the elgi magazine 1 10 apr 2015 - mar 2016 ... the elgi magazine 7 ... the joys of the cruise have a...

THE ELGI MAGAZINE 1

THE ELGI MAGAZINE 2

Send in your letters, faxes and e-mails to:

THE ELGI MAGAZINECorporate CommunicationsELGI Equipments Ltd.,Trichy Road, Singanallur,Coimbatore - 641005Ph: +91-422-2589555Fax : +91-422-2573697E-mail: [email protected] version available at www.elgi.com

VOLUME 10 APR 2015 - MAR 2016

MANUSCRIPT AND ART

Author:Mr. Kumaran Sathasivam

Layout Design and Editing: STRAIGHT CURVE SOLUTIONS, Chennai

Printed at:THE SAFIRE OFFSET PRINTERS, Sivakasi

Image Courtesy:commons.wikimedia.org, www.shutterstock.com,www.istockphoto.com, www.howstuffworks.com

EDITORIAL NOTEDear Reader,Welcome to the 2015 issue of ELGI Magazine!ELGI air compressors are put to a great many uses, and we find the stories behind the applications very fascinating. And so we present a number of these stories in each issue.The various applications we look at in this edition take us to diverse locations: dockyards and oil platforms, for instance.We are inspired to poetry by the use of compressed air in the manufacture of bearings.If you are visiting Coimbatore, consider taking a trip to the various destinations nearby. In this issue we feature Kumarakom, located on Vembanad Lake, which is renown for backwaters tourism.We look at the sense of sound in our series on Nature and compressed air.Other articles in this issue include a business proposition from ATS ELGI.We hope you enjoy reading the magazine.We look forward to your suggestions and feedback.

Editorial Team

THE ELGI MAGAZINE 3

CONTENTS

412 20 26

32

26A BUSINESS OPPORTUNITYATS-ELGI AUTO CAR WASHER

40

34

46

4STRANGE CONSTELLATIONSBACKWATERS OF KUMARAKOM

12STANDING OUT IN ALL WAYSELGI COMPRESSORS IN MARBLE MINES

20COMPRESSED AIR IN NATUREALL EARS

32TECHNOLOGY IN RHYMEBEARING MANUFACTURE

34EXTREME SYSTEMSELGI-SAUER COMPRESSORSIN SUBMARINES

40 DEEP WATERFAR FROM LANDELGI-SAUER COMPRESSORSIN OIL AND GAS EXRACTION

46HELPING BONES HEALCOMPRESSORS INBONE IMPLANTS MANUFACTURE

52NEW PRODUCTSELGI, ATS-ELGI, ELGI-SAUER

THE ELGI MAGAZINE 4

ConstellationsSTRANGE

B A C K W A T E R S O F K U M A R A K O M

THE ELGI MAGAZINE 5

Constellations

A few hours’ travel away from Coimbatore is an unusual geographical feature. It is actually a set of

interlinked features—lakes, lagoons, rivers and canals—and it is collectively known as the backwaters of Kerala.

The popular images of the idyllic backwaters evoke a certain feeling of timelessness. Imaginably, things have been much the same there for eons. But actually there have been changes recently. In the 1980s and 1990s, the backwaters began to draw the attention of the world. Overnight, as it were, they became a tourist phenomenon, with cruises on houseboats becoming immensely popular.

My backwaters experience began at Kumarakom, on Vembanad Lake. Kumarakom used to be a sleepy town. With the tourism phenomenon, it was transformed. Kumarakom rapidly became a popular tourist destination. A number of smart resorts came up, and the village became a point where one could begin a houseboat cruise. There is a well wooded patch at Kumarakom in which there is a nesting colony of

The popular images of the idyllic backwaters evoke a certain feeling of timelessness. Imaginably, things have been much the same there for eons. But actually there have been changes recently. In the 1980s and 1990s, the backwaters began to draw the attention of the world.

THE ELGI MAGAZINE 6

waterbirds. With the tourism, this sanctuary too became well known. I had heard much about the bird sanctuary but knew little about it. Thus it was to the sanctuary that I proceeded on reaching Kumarakom.

I set off from the water’s edge, with the sun shining powerfully on the expanse of Vembanad Lake behind me. The edge of the water was extremely lush, with aquatic vegetation such as rushes growing with a vigour that bordered on the unseemly. At one spot I could see pneumatophores—the air-breathing roots of mangroves—emerging from the soil at the edge of the water. A cloud of dragonflies hung above a patch of reeds. The dragonflies were conspicuously marked with black and amber—they were all of one species, a species that is called the Variegated Flutterer or the Common Picture Wing. I do like the former name better. Actually, I like the scientific name of this dragonfly, Rhyothemis variegata, even more. But I digress. Let me continue with my narrative.

I walked on into the sanctuary—you can only travel through it on foot. The path wound through tall trees. They cut off the sun’s rays most effectively.

But it was very humid and fairly hot. Everywhere there were shallow pools of water with dead leaves at the bottom that had grown very dark as they decomposed. In some places the water was flowing, and I guessed that the movement was related to the tides, which must be changing the water level of the lake all the time. At other places, screwpines stood in the water, supported by their trademark slanting roots. Creepers, ferns and orchids adorned the trees. The undergrowth was quite dense. On the whole it was an archetypal jungle that I was walking through. But it was also not like any other jungle that I had seen.

There were a number of jungly sounds around me as well. Cicadas produced their loud whining sound from the tree trunks. I also heard the unmistakable loud whistles of the Racket-tailed Drongo. I was surprised because I have always associated this

bird with montane forests. Here it was at sea level, almost at the coast!

There was much more to see as I walked along. And the path kept going on, winding through the forest. There were a number of other birds. There were waterhens, for instance, which I saw crossing the track a number of times. They flapped their absurd short tails as they walked about ungracefully on outsize feet. At one place there was a Jungle Striped Squirrel.

I continued my walk, stopping frequently to watch. I may also add that I was perspiring freely in the intense humidity and heat. There were small turtles at every pool of water. As I approached, they dropped into the water with a soft but audible plop and disappeared. Once in a while I could spot the reptile swimming along, its nostrils protruding above the surface.

I FOUND THE ANSWERS LATER. THE KUMARAKOM ‘FOREST’ IS APPARENTLY

MANMADE. IT WAS CREATED BY THE EFFORTS OF ONE MAN, ALFRED GEORGE BAKER, WHO LIVED IN THE

19TH CENTURY.

THE ELGI MAGAZINE 7

At one spot there were Flying Foxes, which are large fruit bats, in the trees. Sporting maroon-and-white pelage, flapping their leathery black wings, they screeched and complained as they are wont to do. Here and there I saw dragonflies perched on twigs. These were tiny Brachydiplax, with transparent wings. A small black crab sidled across the track once. At the back of my mind, there were questions about the forest all the time. Was it a natural forest? How large was it? Were there other places where such forests could be found?

I found the answers later. The Kumarakom ‘forest’ is apparently manmade. It was created by the efforts of one man, Alfred George Baker, who lived in the 19th century. The son of a Christian missionary who came to India from England, Baker asked the king of Travancore for a grant of 500 acres of wet land at Kumarakom. He wished to cultivate paddy and

coconut on the land. The king gave Baker the land he sought. Using a system of canals and bunds, Baker assiduously made the marshy land fit for growing paddy. He maintained some of the land undisturbed so that birds could nest there.

Baker’s efforts showed the native people how land could be reclaimed from the water. Eventually, in the 20th century, Baker’s lands were sold by his successors.

The path wandered close to one of the narrow ramifications of the lake, and

soon I could see boats in the water. Houses appeared next. The path looped back then, and eventually I reached the heronry. The birds nest at the tops of bushes and trees. A couple of watchtowers have been constructed so that the nesting activities can be observed conveniently.

I could see many active nests. There were probably several hundreds of them. The nesting birds were all egrets, herons and cormorants. The egrets were snow-white, with long legs, necks and beaks. They sported elegant ‘aigrettes’ on their backs and

Clockwise from top left: Cormorant, Rhyothemis variegata, Brahminy Kite, Pond Heron, Flying FoxesRight below : Egret , Shag

THE SIGHTS & SOUNDS

THE ELGI MAGAZINE 8

breasts. Aigrettes are filamentous feathers that have given egrets their name. Occasionally an egret would raise these feathers and present a very exquisite sight. In contrast to the egrets were the shags. These birds were entirely black, except for a white mark on the side of the head. They were also short legged and had short beaks. There were a few Purple Herons to be seen among the crowd of egrets and shags. Purple Herons are similar to egrets in shape, but they are somewhat dark in colour, and they have prominently striped necks. There were also a few Night Herons—smaller, greyish cousins of the Purple Herons—at the heronry. I did not see any chicks at the nests. I suppose the birds were all incubating their eggs.

I returned to the shore of the lake in the evening. The sun set, but light lingered on for a long time. I could see a lot of activity in the sky in the twilight. Night Herons went flying past now and then, uttering short guttural sounds. Large numbers of Flying Foxes emerged, setting out for the night. I believe they came straight to the lake to slake their thirst since the day had been quite warm. They seemed to be suspended above the water much as the dragonflies had been in the daytime. There were strange constellations indeed, at Kumarakom! If the Flying Foxes were metaphorically stars or planets, then the Whistling Teals were meteors. Whistling Teals are ducks, and they were flapping past rapidly in groups. They called to each other constantly in high pitched voices. I guess that there was a lot of activity in the firmament above the lake even after it became quite dark.

The next day I went on a cruise on one of the houseboats which are so popular now. I boarded my boat at one of the quiet branches of the lake. The boat had a slender prow and stern, but overall it had a broad construction. It had a picturesque superstructure of wood and thatch. If truth be told, the entire boat was made of wood. On the cruise I passed many other houseboats, and all of them seemed to have been built to the same design.

The boat set off at a very gentle pace, and I explored the vessel. There were two comfortable looking bedrooms on

it. In the aft section was a kitchen. The engine was located below this kitchen. The boat had a steering wheel at the bow. The space on the deck between the wheel and the superstructure was covered above but open at the sides and front. This space was well appointed. There was a good view almost all around.

The engine was remarkably silent. The boat slid past the resorts strung out along the Water Hyacinth-decorated shore. Even when the boat moved into the open, where the depth was presumably too great, small breakaway rafts of Water Hyacinth drifted past. They continued to do this throughout the cruise.

The joys of the cruise have a certain dreamy quality to them. One sits back and relaxes, enjoying the fact that whereas the sun is beating down very energetically on the lake, one is protected by the roof and that the movement of the boat provides a refreshing breeze. One slips into one’s reflections, half alert to events in the surroundings. After all, these events do not make onerous demands! They are restricted to happenings such as the sudden emergence at the water’s surface of a cormorant that has been swimming unseen in the water hitherto. The cormorant spies the boat and apparently cannot believe its eyes. It seems to blink hoping that the boat will not approach it any closer. But the

THE ELGI MAGAZINE 9

boat heads towards the bird, and the cormorant explodes from the water with an effort. It flies low and disappears shortly.

At other times excitement is generated by a tern flying past on slim, pointed wings. It is the essence of grace as it moves, sailing along lightly and scanning the water. Terns, like cormorants, have a penchant for piscine food.

All is well with the world, and there is a crew consisting of the pilot, a cook and a general attendant to take care of one. This is a setting where one makes oneself more comfortable and slips into one’s thoughts. ‘Real life’ is normally too busy to indulge oneself such. On a houseboat, one takes stock of one’s life, one philosophises. All events such as take place do so in one’s head. One could sleep very peacefully in this situation. One only needs to wake up for a meal, which will be served on a proper table on the deck.

One could see, as I did, the astonishing sight of what appears to be a wall built in the lake. This is the

Thanneermukkom bund, a two kilometre long barrier built in the water. Apparently it prevents the movement of salty water from the seaward side of the lake towards rice fields on the other side and thus permits more crops of paddy to be grown there. Would you have believed that you could prevent saltwater and freshwater from mixing by simply building a relatively short length of wall where they meet?

One could catch a glimpse of the aforementioned fields, in Kuttanad. This fertile region has been described as the rice bowl of Kerala. It is a low-lying region, and parts of it are situated below sea level. Outright flooding is prevented through assiduous bund building and maintenance.

The boat was halted close to a bund for lunch. The vessel was tied fast to coconut trees growing on the bund. I could not help noting even as I ate that many Rhyothemis variegata were hovering above the bushes below the coconut

ON A HOUSEBOAT, ONE TAKES STOCK OF ONE’S LIFE, ONE PHILOSOPHISES. ‘REAL LIFE’ IS NORMALLY TOO BUSY TO INDULGE ONESELF SUCH.

THE ELGI MAGAZINE 10

trees. The eye-catching clouds of Rhyothemis v. remain an enduring image of my impressions of Vembanad Lake.

The boat was unfastened after lunch, and soon it turned about in a great circle. It was past midday, and the temperature dropped a little. I could see a sizeable tree-covered island far away. The boat proceeded towards the island at a leisurely pace. It was an island of the kind that inspires stories about treasures and ruthless men. It looked like the sort of island where there is adventure at each step. Even its name suggested adventure: this was Padhiramanal (Malayalam for midnight) Island. Unfortunately only smaller boats could land there. So I had to be content with viewing it from a distance. As my boat hove close, I noted with a slight sense of disappointment that there were a few coconut trees to be seen on the island. Coconuts! How civilised! The island should have been covered entirely with forest trees, and there should have been deadly perils lurking at every turn. Ah well.

COCONUTS! HOW CIVILISED! THE ISLAND SHOULD HAVE BEEN COVERED ENTIRELY WITH FOREST TREES, AND THERE SHOULD HAVE BEEN DEADLY PERILS LURKING AT EVERY TURN. AH WELL.

My cruise ended with an approach to a series of sluice gates built across a neck of the lake. At one end was a lock, built to allow the passage of boats from one side of the gates to the other. Where else can you find such locks in India but in the backwaters? Where else can you find a sign that reads ‘Kochi 42 km, National Waterway—3’? Just think about it, National Waterway, not National Highway!

NATIONAL WATER WAY No.3

Engineering your future energy savings via innovative solutions

80+years of recognizedinnovation experience

See how tomorrow’s solutions are ready todayvisit www.danfoss.com/India | Phone: +91 44 6650 1555


ADV E R T I S EMEN T

Engineering your future energy savings via innovative solutions

80+years of recognizedinnovation experience

See how tomorrow’s solutions are ready todayvisit www.danfoss.com/India | Phone: +91 44 6650 1555


Standing Out in All Ways

Typically, these compressors operate from the bottom of a great oval depression

in the ground, a few hundred feet or so deep. The walls of the depression are

smooth and almost vertical. The sides are indented in a fashion that puts you in mind of extraordinary staircases, with the risers going up tens of feet while the treads are just a few centimetres or so broad. These ‘steps’ are also suggestive of the seats of

a ridiculously designed amphitheatre. Something about them suggests that they

have been created by human agency.

Clue 3

These compressors are trolley mounted machines. But unlike the majority of trolley mounted

compressors, they are electrically powered, not driven by diesel

engines.

Clue 1

Some Elgi air compressors are used in the most uncommon applications. Other Elgi compressors that are put to mundane uses are distinguished by the locations they work in—these locations are exotic in some instances, and in others they are extreme—occasionally, the locations are both exotic and extreme at the same time. And then there are some compressors that stand out in all these ways. This article is about a set of compressors that belong to this last group.Here are some clues about how and where these particular Elgi machines are deployed. Perhaps you would care to identify the location and the application? They are used outdoors, in

locations open to the sky. Characteristically, the sun shines down brightly on

them.

Clue 2


The immediate surroundings are rugged and rocky or piled

with great mounds of earth and stone. The rocks and

stones are white or very lightly coloured. The landscape in the vicinity is very arid and on the

whole somewhat lunar.

Clue 4 But here and there, water seeps down the walls of the ‘amphitheatre’, making a dark

stain of moss or salt, it is difficult to say which. A few shrubs or short trees have established themselves on the vertical

walls. Life is evident in a couple of other forms as well in an otherwise sterile

environment: there is a hive of rock bees high up on the walls, and pigeons are flying

about. The birds are clearly interested in drinking the water that has formed a broad

sheet at the bottom of the pit. There is a white powder that has settled everywhere

below, including in the water, imparting it a curious bluish colour.

Clue 5

There are several derricks around the edge of the pit.

And there are numerous earthmovers inside.

Clue 6

The compressors supply compressed air to an unpretentious looking

machine that drills 4-inch holes in the ground.

Clue 7

It is usually quite hot in the daytime. The temperature

in summer is in the 40s (degrees Celsius, that is).

Clue 8

The product of this application is a material

that has been prized since ancient times. At some

times it was considered a royal material, but it is now

used widely.

Clue 9 ANYGUESSES?


What did you guess? Give yourself one point if you identified a mining application after Clue 9.

If you thought it was marble mining, you are correct! Give yourself two points then. If you thought the location was Rajasthan, again you are right—give yourself two points.

If you got both the application and the location correct, give yourself two bonus points. If you needed fewer than nine clues to guess the answer, give yourself an extra point for each clue less.

Give yourself two extra points for each—give yourself three—treat yourself to lots of points!

Anyway, folks, the clues describe to you a common setting in a marble mine in Rajasthan,

famous as a tourist destination, the leading marble producing state of India. As a matter of fact, Rajasthan enjoys a near-monopoly as a marble supplier. There are just a couple of other states in the country, to wit Gujarat and Madhya Pradesh, that have any significant marble resources. And it is to be noted here that India is said to be the third largest producer of marble in the world, contributing 10 percent of global production (Italy stands first, with 20 percent, and China is next, with 16 percent).

Marble is a form of limestone that has been recrystallised naturally under intense heat and pressure. This metamorphosed rock is composed mostly of calcite and dolomite. The characteristic swirls of marble are caused by impurities such as silt and clay that were present in

the original limestone as layers or grains. A green colour may be produced by serpentine or tremolite.

Marble has been the preferred stone of many sculptors because of its physical properties. It is easy to carve. At the same time, it is fairly resistant to shattering. It is also homogeneous. Above all, light penetrates several millimetres into marble before being scattered out—marble owes its trademark waxy look to this last property.

The other major use of marble is of course as a construction stone. It is capable of taking polish, and its popularity as a flooring material is well known. Marble has been used as a construction material for a long time. That marble from Rajasthan has been used in architecture ‘from time immemorial’ is supported by a series of monuments and temples: the Victoria Memorial, Kolkata (early

20th century); the Taj Mahal (17th century); the Ranakpur Temple, Pali, Rajasthan (15th century); Dilwara Temple, Mount Abu, Rajasthan (11th century to 13th century). The presence of marble in the Rajasthan region may have been known even longer.

But systematic efforts to document the marble wealth of India probably began only in the middle of the 19th century, when the East India Company formed a Coal Committee to study the availability of coal in parts of India. Other such committees were formed next, and geological surveyors were appointed. The Geological Survey of India was established in 1851, and its scope of work expanded quickly from coal to oil and ore deposits and to geological studies in general and mapping mineral resources.

Rajasthan’s reserves of good quality marble are estimated at 1100 million tonnes. These reserves are known

THE POINTS TABLE


p

to be distributed widely across this large state: around Nagaur, Jaipur, Alwar, Dausa, Jaisalmer, Rajsamand, Pali, Banswara, Udaipur, Bundi, Sirohi, Ajmer, Sikar, Jodhpur, Chittaurgarh, Churu…

Anyone who proposes to commence marble mining operations must identify an area that has been earmarked for mining and purchase a suitable extent of land therein. An environmental clearance must be obtained before mining can begin.

1

2

3 4

RAJASTHAN’S RESERVES OF GOOD QUALITY MARBLE ARE ESTIMATED AT 1100 MILLION TONNES.

1. Victoria Memorial 2. Taj Mahal 3. Ranakpur Temple, Pali, Rajasthan 4. Dilwara Temple, Mount Abu


In some instances the marble is found at the surface, but it may also lie under a mass of material known as ‘overburden’. The depth of the overburden could be 100 feet or so in places. It is essentially made up of earth, stones and rocks. The location and quality of the underlying marble must be determined by a core drilling operation. A core drill yields a cylinder of material from underground. Core samples are analysed by geologists before a mining company decides to begin mining in a particular place.

The overburden, if any, is removed using earthmovers. Usually this mass of material is simply heaped near the mine because it is too expensive to transport it anywhere else.

Once the marble rock is exposed, blocks must be cut from it. Larger blocks fetch better rates, and so the size of a marble block tends to be that of the largest one that can be conveniently handled. In practice marble blocks from mines are rectangular solids, and they could be 40 feet long, with corresponding widths and heights. Their weights could be as high as 20 to 30 tonnes.

When a block is to be cut, its corners are marked on the rock, and vertical holes are drilled at these points. The machine used in this crucial operation is a ‘slim drill’ or a ‘wagon drill’, which is mounted on wheels. It looks modest, but it is versatile and can drill both horizontal and vertical holes. It is this machine that is driven by compressed air. It has two air motors: one lifts the drill bit and brings it down on the rock, while the other air motor rotates the drill bit simultaneously. The end of the bit itself has buttons with diamonds embedded in them. If you looked at these buttons, you would

The machine used in this crucial operation is a ‘slim drill’ or a ‘wagon drill’, which is mounted on wheels. It looks modest, but it is versatile and can drill both horizontal and vertical holes. It is this machine that is driven by compressed air.

1

2 3

4

1. Slim drill 2. Drill bit 3. Vertical 4 inch hole 4. ELGI ET compressor


not say that they had diamonds on them. The diamonds are too small and uncut, and they do not sparkle. The rotating and linear motion of the bit against the rock produces a hole. The hole is usually 4 inches in diameter. The length of the bit can be increased through the use of extenders as the hole grows deeper

Once the vertical holes are drilled, the wagon drill (or slim drill) is used to drill horizontal holes corresponding to the horizontal edges of the block. The vertical and horizontal holes that have been drilled around the rock need to meet for the sawing operation to begin. Thus some precision is required in marking and drilling them.

To cut one face of a block, a wire saw is threaded through the vertical and horizontal holes corresponding to that face. A wire saw, despite its name, does not look like a saw at all. It is a cable covered entirely with a series of helical springs and short metallic sleeves passed around it. The sleeves, like the bit of a slim drill or wagon drill, have diamonds embedded on them to cut the marble. Again, you would not say that there were diamonds on the sleeves if you looked at them. And the sleeves do not feel particularly

rough or hard to the touch. Talking of diamonds, a wire saw is referred to at the mines as a ‘mala’ (necklace) because of its appearance.

Once the wire saw has been passed through the holes in the rock, its ends are passed around a large pulley and fastened together. The pulley is then driven, causing the wire saw to turn and the sleeves to rub against the marble, abrading it. Slowly, the wire saw cuts through the marble. The saw must be cooled because it heats up, and so water is constantly sprayed along it. If ground water seeps into the mine, it serves as a ready source of cooling liquid. The springs on the wire saw serve to keep the sleeves apart during the cutting operation. And the sleeves themselves are not fixed firmly on the cable because the cable would be too stiff if they were.

Once cuts have been made corresponding to the sides of the marble block, a cut must be made along its bottom. This calls for another drilling operation. A horizontal hole is made at the back of the bottom surface of the block now, and the wire saw is deployed again. When the horizontal cut has been made, the block is free to be lifted out. One

ABOVE-FROM LEFT :DIAMOND PELLETS ON THE WIRE,THE SAWING PROCESS, THE DERRICKUSED TO LIFT THE CUT BLOCKSBELOW-FAR RIGHT :EARTH MOVERS WAITINGFOR REPAIR


of the derricks around the edge of the mine is used to lift the block. The block is placed on an earthmover, which transports it out of the pit. The block could be lifted straight out using a derrick itself, but this is a slow process—the earthmovers are much quicker.The marble blocks from the mine will be transported to one of the many processing units in Rajasthan. In the processing unit, the blocks will be cut using a gangsaw, which has a number of blades. Thus the blocks will be sliced like so many loaves of bread. The slabs will be bought by customers, possibly from far away. These slabs, ‘pieces of Rajasthan forever’, will adorn the floors and walls of houses, offices and other buildings all over the country and abroad.

Marble mining is ‘big business’. Work goes on around the clock at a marble mine. Workers live on the site for extended periods since the mines are usually located at remote places and they cannot commute daily. The mining company arranges facilities such as drinking water (shipped in tankers to the mine) and a canteen where they get their meals.

Mining calls for large investments—the cranes and earthmovers are expensive. This means that none of these machines can be kept idle. A workshop is built at the site so that repairs can be carried out. And yes, the compressor must run day and night, heat, dust and all.

TALKING OF DIAMONDS, A WIRE SAW IS REFERRED TO AT THE MINES AS A ‘MALA’ (NECKLACE) BECAUSE OF ITS APPEARANCE.


ALLEARS

compressed air in nature


If you ask a physicist for a good reference book on sound, he or she may well recommend to you a two-volume work by John William Strutt (Baron Rayleigh).

This book, The Theory of Sound, was published in 1877 and 1878. The extended currency of this book, over close to a century and a half, suggests that the treatment of the subject was quite comprehensive—one is tempted to say that the treatment was very sound. The writing style that John William Strutt, or Baron Rayleigh if you will, used belongs to a bygone period, and that style too defies improvement.

‘The sensation of sound is a thing sui generis,’ writes Rayleigh, ‘not comparable with any of our other sensations. No one can express the relation between a sound and a colour or a smell.’

On reflection, it is also impossible to write down many sounds as words, even common ones—such as the chime of a bell or the trill of a bird. The alphabet and written language are simply not capable of dealing with sounds other than those of the syllables of the spoken language. As Rayleigh puts it, ‘Directly or indirectly, all questions connected with this subject must come for decision to the ear, as the organ of learning.’

Indeed, sound is very closely associated with our ears. Invoking the words of Rayleigh again, ‘Without ears we should hardly care more about vibrations than without eyes we should care about light’. In effect, sound is all about ears. But ‘… we are not therefore to infer that all acoustical investigations are conducted with the unassisted ear. When once we have discovered the physical phenomena which constitute the foundation of sound, our explorations are in great measure transferred to another field lying within the dominion of the principles of Mechanics. Important laws are in this way arrived at, to which the sensations of the ear cannot but confirm.’

Just as sound is strongly associated with ears, so too is it related to vibrating bodies. It is common knowledge that anything producing a sound is in a state of vibration—a drum, a string, our vocal chords and so forth. As soon as the vibration is damped, the sound stops. It is also well known that for a sound to be heard, there needs to be an uninterrupted medium between the source of the sound and the ear.

Happily for us, the air surrounding us remains continuous at all times—it is not given to developing pockets of vacuum

Only two animal groups have evolved the ability to hear-vertebrates like mammals, birds and reptiles; and arthropods, such as insects, spiders and crabs. No other animals can hear.Source: www.nms.ac.uk/our_museums/national_museum/explore_the_galler-ies/natural_world?animal_senses.aspx

ONLY TWO ANIMAL GROUPS

‘The sensation of sound is a thing sui generis,’ writes Rayleigh, ‘not comparable with any of our other sensations. No one can express the relation between a sound and a colour or a smell.’


spontaneously. That is why we are free to do in an uninterrupted fashion the numerous things facilitated by sound—holding conservations with others, hearing announcements at railway stations or airports, listening to musical performances of orchestras.

Talking of music, it is thanks to a certain property of sound that we hear the aforesaid musical performance as we do. This is the property that for all practical purposes sound travels at the same velocity regardless of its intensity or pitch. Imagine the disorder that would result if the sounds from different instruments of the orchestra travelled at different speeds! These sounds might set out from the instruments simultaneously, but the sound of the drums, for example, might reach your ears long after the sound of the flute or the violin reaches you. What if louder sounds travelled faster than softer ones? You would hear the loud sounds first and then, after a delay, the softer ones. It would all be very cacophonous and… well, it would not be music as we understand it.

The speed of sound does change with temperature—but the change is really not sufficient to make any difference in daily life. And the speed gets affected by movement of air too. A wind will change the velocity of sound, depending on the direction in which it is blowing.

As school physics textbooks tell us, sound travels through air as longitudinal waves. These waves consist of alternate regions of compressions and rarefactions of air generated around the source of

sound. When the sound travels from the source to a listener (or any other point), what moves is the series of rarefactions and compressions—a pressure oscillation is set up at each point around the source; there is, of course, no rush of air such as produced by a fan. When the level of rarefaction or compression is greater than a certain threshold, the oscillation is perceived as sound. The

number of oscillations produced in a given period of time, the frequency of the sound, must also be within a certain range to be sensed by the ear.The ear, of course, is vital to hearing, but another organ has a major role as well: the brain. The brain receives auditory signals and processes them (in ways we do not completely understand) so that we have the sensation of hearing. Areas

THE EARWhat is commonly referred to as ‘the ear’ is actually only the visible part of the external ear. This is anatomically called the pinna, auricle or auricula. The small, pointed protuberance is the tragus. The fleshy part at the bottom of the pinna is the lobe. And the part immediately above the lobe is called the anti-tragus.

Pinna

Ear canal

Tympanum

Malleus andincus


The amplitude of a sound wave can be expressed in terms of the maximum pressure change at the eardrum, but a relative scale is more convenient. The decibel scale is such a scale. The intensity of a sound in bels is the logarithm of the ratio of the intensity of that sound and a standard sound. A decibel (dB) is 0.1 bel. Therefore,Number of dB = 10 log(intensity of sound/intensity of standard sound)Sound intensity is proportionate to the square of sound pressure. Therefore,Number of dB = 20 log(pressure of sound/pressure of standard sound)The standard sound reference level adopted by the Acoustical Society of America corresponds to 0 dB at a pressure level of 0.000204 dyne/cm2 [1 dyne/cm2 is a thousandth of a millibar], a value that is just at the auditory threshold for the average human.

Source: Ganong’s Review of Medical Physiology, by Kim Barrett, Heddwen Brooks, Scott Boitano and Susan Barman, 23rd edition, McGraw Hill, 2010.

The Threshold of Hearing

of the brain with names such as the dorsal and ventral cochlear nuclei, the inferior coliculi, the medial geniculate body, the auditory cortex and the olivocochlear bundle are all involved in hearing. Through the use of techniques such as positron emission tomography (PET) scanning and functional magnetic resonance imaging (fMRI), our knowledge about how the brain processes auditory

information is growing rapidly. But there are findings that need to be explained. In engineering terms, the ear acts as a system that converts sound into electrical signals and feeds these to the brain through nerves.

The ear is a complex device, most of it located in an inaccessible part of the head. What is visible—‘the ear’—is the pinna, which serves to funnel

Tympaniccavity

Eustachian tube

Cochlea

Semi-circularcanals


the hair cells. This shearing action produces an electrochemical signal which is picked up by the auditory nerve.

The elaborate mechanism of the ear in humans is sensitive to sound frequencies ranging from a minimum of 20 Hz (or cycles per second) to an upper limit of 20,000 Hz (20 kHz). Thus the highest frequency that is audible to humans is a thousand times higher than the lowest one. Other animals, best known among which are dogs and bats, have ears that are sensitive to much higher frequencies.

The range of sound intensities that the ear can process starts at 0 dB, at the threshold of hearing. It must be noted that 0 dB does not mean a lack of sound but a sound level equal to a standard. The sound level of a rustling leaf is 10 dB, and the level

in a ‘quiet’ room is around 25 dB. A normal conversation at a distance of 1 metre is around 50 dB. Household electrical devices and television sets generate 60 dB or so, while a car at 10 metres may produce 80 dB. Loud tools such as jackhammers produce sounds of around 100 dB, and jet engines at 100 metres generate up to 140 dB.

Prolonged exposure to sounds of 85 dB and more can lead to hearing damage. The ear has a protective mechanism: when it faces very loud sounds, there is reflex contraction of muscles in the middle ear, which dampens sound conduction. Sounds of 120 to 130 dB cause pain, and there is a risk that hearing loss will be induced. At 140 dB, the organ of Corti is potentially damaged.

What are the pressures produced by these loud sounds? The answer is that

sound into the external ear, along the auditory canal. The canal terminates at the eardrum. Beyond the eardrum is the middle ear, an air-filled cavity in which three small bones are situated. These are the malleus, incus and stapes (Latin for hammer, anvil and stirrup, respectively), named for their shapes. The three bones link the eardrum to the oval window, which leads to the inner ear. In this section of the ear are the cochlea, a coiled tube, and the semicircular canals. The canals are a set of three mutually perpendicular canals, and they play a role in maintaining the sense of balance.

When sound strikes the ear, the pressure disturbance makes the eardrum move. The bones of the ear act as interlinked levers, magnifying the movement (by a factor of 1.3) and acting on the oval window. The pressure of the stirrup on the oval window sets up pressure waves in the perilymph, a fluid within the cochlea. The area of the eardrum is 17 times greater than that of the oval window. Thus the pressure set up in the perilymph is more than 22 times the sound pressure that generated it. Key to the conversion of the mechanical movements of the perilymph into electrical impulses (‘action potentials’) in the auditory nerve are the auditory hair cells, within a part of the cochlea known as the organ of Corti. The movements of fluids and membranes within the cochlea cause a shearing back and forth of stereocilia, which are organelles in

The greatest atmospheric pressure recorded ever in the world was 1094 millibars; the lowest was 870 millibars. Now consider hearing. The largest sound pressures are created by those painful 140 dB sounds: these are a mere 2 millibars.


the entire range of pressure levels associated with sound lies in a realm far removed from the world of air compressors. Compressors typically produce air pressures of 7 bar (7000 millibars) and commonly generate much higher pressures.

To provide a perspective, atmospheric pressure at sea level is 1013.25 millibars, with 1 millibar being one thousandth of a bar. At a height of 2000 metres above sea level, the pressure drops to around 800 millibars. Underwater, the pressure rises, rather more rapidly—at some 1000 millibars with each 10 metres. The ear is sensitive and needs to be protected from these changes. The middle ear is hollow, and so if we move to a high altitude or dive, we create a pressure difference across the eardrum. If this pressure difference is sufficiently high and if it is not relieved, it can damage or

burst the eardrum. The Eustachian tubes, connecting the inner ear and the nasopharynx, serve to equalise the pressure within the middle ear and the air pressure. Normally the Eustachian tubes are closed at the nose end to prevent entry of mucus. But when the jaw is protruded or lowered, such as when we chew or yawn, they are opened, making the pressures the same.

The atmospheric pressure also changes according to the weather. It may even vary on an hourly basis. But these variations are very mild compared with the changes due to altitude. The greatest atmospheric pressure recorded ever in the world was 1094 millibars; the lowest was 870 millibars. These measurements were both made during extreme weather events—the former during a prolonged spell of very cold weather in Russia and the latter during a

typhoon. Normally, the atmospheric pressure may vary by just 20 millibars or so across a large land mass.

Now consider hearing. The largest sound pressures are created by those painful 140 dB sounds: these are a mere 2 millibars. Gentler sounds naturally produce much lower pressures. And the span of 0 to 140 dB that the ear can cope with represents a 10 million-fold variation in the sound pressure. At the threshold of hearing, therefore, the pressure level is an astonishing two ten-thousandths of a microbar—a microbar is a thousandth of a millibar! This pressure may be scarcely detectable, and the level may scarcely qualify as compression, but there you are, in sound you have a ubiquitous representative of compressed air in nature.

Comparison between pressures of compressors and the ear


A BUSINESSOPPORTUNITYATS-ELGI AUTOMATIC CAR WASHER


THE ATS ELGI SMART WASH IS A VERY MODERN CAR WASHING SYSTEM. IT OFFERS NUMEROUS ADVANTAGES TO CAR OWNERS AND GARAGES ALIKE. INVESTING IN THE ATS ELGI SMART WASH MAKES FOR A SOUND BUSINESS ENTERPRISE.

Cars have become ubiquitous and are available in a large number of makes and models

today. The world car production has nearly doubled over the decade. India has become the sixth largest car manufacturer in the world with a four fold increase in car production. As a result, vehicle servicing is a burgeoning business.

At the same time, it is also a demanding business. Customers, enjoying the benefits of choice, select vehicles from a variety of shapes and sizes. They expect high standards from both the product and the servicing of the vehicle. Vehicle owners expect professional servicing and faster service times.

In today’s market, a car service business is rated on customer

satisfaction. The appearance and cleanliness of vehicles play a vital role in achieving this satisfaction. In this situation, maintaining a uniform wash quality and improving washing techniques are essential.

This seems to have been recognised even a hundred years back. In 1914, a couple of gentlemen are said to have opened an ‘automated car laundry’ in Detroit. Automated car washers have developed since then, and they have a niche for themselves in garages, service centres and petrol bunks that offer drive-in washing. Whereas most of the diverse gear in a garage is meant for repairing and maintaining engines, keeping mechanical parts in trim and so forth, there is one piece of equipment that cleans a vehicle and makes it look good, the automatic car washer.


The ATS ELGI Smart Wash is a very modern car washing system. It offers numerous advantages to car owners and garages alike. Investing in the ATS ELGI Smart Wash makes for a sound business enterprise.

The main component of the Smart Wash is a gantry, vibrantly painted in red, that moves on a pair of parallel rails. The gantry, made of rust-proof galvanised iron, is a rectangular bridge-like frame designed to move on the rails. The wash bay comprises the area covered by the gantry and rails. A water drainage pit is provided between the rails, and a chequered stopper is provided on one side of

this pit. No washing hoist or washing ramp is required.

There are 21 spray nozzles strategically positioned around the gantry to direct water, shampoo or wax all over the car. Three sprays located on the horizontal column of the gantry direct water on the vehicle from above; there are two arrays of vertical sprays on either side of the gantry; and there is a pair of rotating nozzles mounted on a moving carriage to direct high-pressure water on the under-chassis.

The Smart Wash features a set of three brushes. The brushes are made up of

smooth polyethylene bristles. One brush is mounted horizontally such that it travels vertically and scrubs the top surface of the car. The other two brushes are of similar construction and are provided on either side of the gantry. These are vertically oriented and are capable of moving in and out of the wash bay. They clean the front, sides and rear of the car most effectively. Additionally, wheel brushes are provided on either side to clean the wheels. They are brightly coloured and bestow a cheerful look on any garage.

An overhead high-capacity blower is mounted on the gantry. The blower

SMART WASH21 Spray Nozzles to direct water, shampoo or wax all over the car.

3 Polyethylene smooth bristle brushes

Disk Wheel Wash for wheels


follows the contour of the car and blows away water droplets on the body. Simultaneously, side blowers blow air in an optimal direction from the top of the windows down to the rims.

A system of sensors is an important feature of the Smart Wash. The sensors completely control the working of the machine. The signals provided by these sensors are fed to a programmable logic controller which governs the operation of the car washing system.

Preparation of a car for an automatic wash consists of cleaning the engine

A system of sensors is an important feature of the Smart Wash. The sensors completely control the working of the machine.

compartment and the wheel arches. (A trigger gun with adjustable flow is provided for washing the wheel arches and the engine compartment.) The windows are raised fully, the outer rear view mirrors are folded back and the radio antennas, if any, are removed. The car is now driven on to the washing bay and positioned in alignment with the chequered stoppers. The Smart Wash is switched on. The wash that follows is entirely automated.

The gantry moves from the front end of the car to the rear, rinsing the vehicle with water to loosen any dirt. The gantry sprays car shampoo

Overhead and Side Blower for comprehensive drying

Under Chassis Wash System for a total washing performance

6-7 minutes/ car


over the body. This cleaning solution is specially formulated to not only loosen and remove grime but also impart an after-wash glow to the surface.

Simultaneously, the under-chassis is washed by jets of high-pressure water produced by the rotating nozzles. The nozzles move on a carriage delivering water at a high pressure, ensuring that all the dirt and grime is dislodged

When the gantry reaches the end of the car, the sensors stop it from moving further, and the horizontal and vertical brushes start to spin at an optimum speed. By centrifugal action, the bristles spread out. The horizontal brush moves down from its home position at the top, till it is close to the boot. The vertical brushes move inward. A spray of water wets the brushes at the same time. The

combination of the movement of the horizontal and vertical brushes and the action of the long, spinning bristles is a surprisingly simple but effective means of cleaning any complex contour. Every part of the vehicle’s surface is gently, yet thoroughly, cleaned—grill, rear bumper, rear windshield.

The gantry starts moving back towards the front of the car. The horizontal and vertical brushes are moved upward and outward, respectively. They follow the contours of the vehicle so that the body of the car is wiped clean as the gantry proceeds. The brush speed and pressure are continuously monitored by a control system.

When the gantry passes over the front end of the roof, the sensors cause the horizontal brush to move down,

cleaning the front windshield and the bonnet.

As the gantry reaches the end of the car, the vertical brushes move inward, cleaning the front bumper and the radiator grill.

When the gantry is in line with the front wheels, it stops. The wheel brushes extend and spin, cleaning the wheels and the front tyres. The wheel brushes are stopped and retracted, and the gantry proceeds to the rear wheels, which in turn are cleaned. The vertical and horizontal brushes clean the car further as the gantry moves to the rear of the vehicle.

During the next pass, the gantry sprays a wax solution over the car. The specially designed wax facilitates faster drying and gives a glossy finish to the car.

Now the blower moves over the car with a steady flow of air from the top and the sides. The air stream envelops the vehicle, drying it rapidly, and the car is ready to move out.

Productivity and Quality improvement studies carried out by ATS ELGI show that the payback period for a Smart Wash used to wash 40 to 50 cars a day is less than 2 years.


The entire operation takes just between 6 and 7 minutes.

The Smart Wash offers several advantages over manual washing:

1. The time required to wash a car is reduced (by nearly half), and productivity is increased.

2. The manpower requirement is reduced (again to around half). At the same time, worker retention is improved. Manual washing is tedious work, and so attrition is high with manual systems.

3. The consumption of water and consumables is controlled. The Smart Wash reduces water consumption by a third.

4. The washing quality is superior to that of manual washing, and it is uniform, whereas the quality is variable in manual washing.

5. The gloss of the vehicle is improved.

6. Customer retention is good, and new customers, particularly

owners of high-end cars, are attracted.

7. During manual washing, a worker is constantly exposed to dirt, diesel fumes and grease. But with the Smart Wash, there are no health hazards whatsoever.

Thus not only is it desirable to have one’s car cleaned using the Smart Wash, it would also be a good business proposition, as mentioned previously, to invest in the equipment. Productivity and quality improvement studies carried out by ATS ELGI show that the payback period for a Smart Wash used to wash 40 to 50 cars a day is less than 2 years. The critical components of the ATS ELGI Smart Wash are made of stainless steel and hot dip galvanised iron for extended life. It is perfectly feasible for entrepreneurs to start even a chain of automatic car washing garages offering uniform, superior-quality service. ATS ELGI has the investment calculations and business plans. Are you interested? If yes, just write to Prasanth Thiagarajan ([email protected]).

THE SEQUENCE


Learning about machines, technology and the like is funParticularly when it is doneThrough poetry—the metre could be relaxed, and one only needs to be strict about rhymeEngineering textbooks should be in verse. Why has no one thought of it? It is high time!

Take for instance this workIt is about ‘invisible heroes’ that in common machines lurkWithout them (the heroes, that is) parts would need to be replaced in a manner ceaselessFriction would be wearing components out like axles greaseless

You know them (these unnoticed heroes again) as bearingsNot to be confused with fairingsThey keep wheels spinning—and of course shafts and rotorsIn everything from bicycles to electric motors

A bearing get its name from ‘to bear’,As it supports (‘bears’) another element, which is an explanation fairThus, if a shaft rotates within an orificeYou have a bearing surface

You could introduce on top of such a surface a metallic layerAnd you would get a bearing metal, the etymology is quite clearIf you used a separate sleeve, it would be of the type ‘discrete’Fused to the substrate, it would only be ‘semi-discrete’, but still, it would be a bearing neat

So much then for terminology; these simple thingsThese ‘plain bearings’Are widely used, often with lubricant (in quantities large or just a spot)But the engineer, of ball and roller bearings he or she thinks a lot

Some of these are extremely precise devices, you will allowThe technology involved will make you lift your eyebrowTo appearances, even a run-of-the-mill bearing is rather complexIts multitude of parts may perplex

But it is all quite simple: first there is an inner ringThat’s literally the central feature of the thingTo make this part you need to ‘turn’ metal, give it heat treatmentAnd grind it and hone it—ah, the job is done, that’s an achievement!

Where there is an inner ring, there should be an outer ring, and so there is in verityAnd between the manners in which they are made there is a great similarityThese is a gap between these two rings, the inner and outerAs can be verified by dismantling them by any doubter

The invention of the rolling bearing, in the form of wooden rollers supporting, or bearing, an object being moved is of great antiquity, and may predate the invention of the wheel.

Though it is often claimed that the Egyptians used roller bearings in the form of tree trunks under sleds, this is modern speculation. They are depicted in their own drawings in the tomb of Djehutihotep as moving massive stone blocks on sledges with the runners lubricated with a liquid which would constitute a plain bearing. There are also Egyptian drawings of bearings used with hand drills.

The earliest recovered example of a rolling element bearing is a wooden ball bearing supporting a rotating table from the remains of the Roman Nemi ships in Lake Nemi, Italy. The wrecks were dated to 40 BC.

THE ANTIQUITY OF BEARINGS

BEARING MANUFACTURE

Technology in Rhyme


WHAT BEARINGS ARE?A bearing is a machine element that constrains rela-tive motion and reduces friction between moving parts to only the desired motion. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by con-trolling the vectors of normal forces that bear on the moving parts. Many bearings also facilitate the desired motion as much as possible, such as by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts.

Source: Wikipedia

PRECISIONBearing components are manufactured so that their dimensions are extremely accurate. The dimensions of an inner ring may vary by no more than 40 microns from the stated measurements.

COMPRESSED AIR IN BEARING MANUFACTURECompressed air is used to clean bearing components when they are being machined. It is also used to move components from machine to machine and in assembly of the components.Automated machines such as CNC machines operate at high speeds, and air is used to change tool heads and operate spindles. These machines need a supply of clean and dry compressed air.

And there are balls in this spaceHard, metallic marbles in the groove formed between the rings (the groove is called a race)Uniform in size to an extent astonishing, this clone-collectionIs produced by moulding, rolling, grinding, selection

In lieu of the balls there could be rollers or cylinders—their use is quite frequentThey too are subjected to the same treatmentIt is clear that if you are to be a bearing component, it is your lotTo be moulded, ground, made very hot

The balls or rollers or cylinders, as alike as peasThey erode each other with easeFor they tend to cluster if they are not kept apartThings called cages are used for this, contraptions simple but smart

Notwithstanding their nameNot all of them look like cages, not quite the sameThey are pressed out of sheet metal, and in agreement you would nodIf someone remarked that some of them put you in mind of a pea pod

All these thingsCages, rollers, inner rings, outer ringsAre made using a CNC machine or lathe and pressMachines that are powered hydraulically or pneumatically, oh yes

Pneumatic! To power them you need air compressedAren’t you impressedBy this utility, compressed air, which is so essential for industry?Without it, where would bearing manufacture be?

Let us end this ode reflecting how poetry makes simple and easyWhat looked complex and even tedious prima facieWhat a happy thought to think that a manual of manufacturing technologyCould simultaneously be a literary anthology!


Extreme Systemssystems that, at times, come close to being isolated systems. Submarines are among these. Most submarines are used for military purposes, and naturally they must be very stealthy when they are in action. They avoid being detected visually by submerging well below the surface of the water. A submarine must also be very quiet because any sound it produces can be detected by an enemy, giving away its presence. A submarine is totally silent only when all the machinery within it is turned off. One of the subterfuges practiced by submarines is to do just this and lie still on the bottom of the ocean. They may even turn off their air conditioning to avoid making sound, so that they are the same temperature as the water around them. Even when they do this, they can be detected using active sonar, a technique in which pulses of sound are emitted and echoes are listened for. So modern submarines are provided with an anechoic coating, usually a sound-absorbing layer of rubber, on the outer hull. A quiet submarine on the ocean floor is then literally one with the environment, non-existent for all purposes.

When the temperature of the water changes, heat is transferred from the submarine to the water or vice versa.

Except for this, the still submarine is rather like an isolated system.

But submarines cannot lie still for indefinitely long times. It is true that modern submarines do not need to surface for air—they have systems for recycling air and generating oxygen from water through electrolysis. It is also true that if a submarine happens to run on nuclear power, it does not need to surface frequently for fuel—its machines can operate for very long periods without refuelling. And a submarine can even produce fresh water for the crew from seawater. But eventually it will exhaust its stores of food. And so any submarine must rise to the surface some time to replenish these stores.

To rise, or indeed, to dive—to perform any vertical manoeuvre in general—a submarine must alter its state of buoyancy. This is achieved by letting in water from the sea into ballast tanks or by emptying these tanks to the sea. Incidentally, these actions are ‘exchanges of matter with the surroundings’ and as such automatically disqualify a submarine’s candidature as an isolated system.

When a submarine is at the surface, it is said to be in a positively buoyant

THERE ARE SOME SYSTEMS THAT, AT TIMES, COME CLOSE TO BEING ISOLATED SYSTEMS. SUBMARINES ARE AMONG THESE.

The science of thermodynamics classifies physical systems as open, closed or isolated

systems. An open system is one which can exchange matter and energy (in the form of heat or as work) with its surroundings. Many systems encountered in daily life are open systems—a room with open windows and doors, for example, is one: air can move into and out of it, and the room gets hotter and cooler all the time as the temperature of the surroundings changes.

A closed system is one which can exchange energy with its surroundings but does not exchange matter. Examples of closed systems are also not difficult to find. An airtight room is close to a closed system—matter cannot enter or leave it, but it absorbs heat from its surroundings at times and sheds heat to them at others. An electric motor with an airtight construction is another system that might be considered as a closed system. Electrical energy enters it, and the motor performs work on its surroundings.

Isolated systems are systems that do not exchange heat, work or matter with their surroundings. These are ideal systems, and so examples are not found in real life. There are some


Consider anything within the sea, such as a submarine or a fish: the water pressure acts all over its surface. Water pressure at a given point in the sea acts equally in all directions. So the pressure acting on the upper surface of the submarine (or fish) is directed so as to push it down; the pressure on the lower surface acts to push it up. But the magnitude of the pressure increases with depth. Thus the total pressure on the lower surface is greater than the pressure on the upper surface. Thus the resultant vertical force exerted by the water on a body submerged in it is always so as to push that body up. This force is known as the force of buoyancy.

F O R C E O F B U O Y A N C Y

condition, like any ship floating in the water. This refers to the tendency of the craft to rise or return to the floating state if it were to be submerged by external means into the water. A submarine descending into the depths of the ocean, in contrast, is negatively buoyant. The term ‘buoyancy’ is also used for the net force that the water exerts on the submarine. This can be confusing because this force of buoyancy is always in the upward direction, regardless of whether the craft is positively buoyant or negatively buoyant.

What the terms ‘positive’ and ‘negative’ refer to is the direction

DCTs

of the resultant force acting on the submarine. The direction of the force of buoyancy is opposite to that of the weight of the submarine. If the weight is greater than the force of buoyancy, the net force is downward, and the submarine is negatively buoyant. If the weight is less than the force of buoyancy, the net force is upward, and the submarine is positively buoyant. And there is a situation in which a submarine is neutrally buoyant—one in which the downward-acting weight and the upward-acting buoyancy are equal.

When a submarine takes water into its ballast tanks, it effectively

increases its own weight and moves downward. The opposite happens when a submerged submarine rises to the surface: it reduces its own weight by expelling water from its ballast tanks.

During a de-ballasting operation, the ballast tanks of a submarine are opened to the sea. The water in the ballast tank is expelled by increasing the pressure in the tank. It may be pointed out that the pressure of the water in the sea increases by approximately 1 atmosphere for every 10 metres of depth. And submarines may descend to depths of hundreds of metres, with correspondingly high

SURFACE

BOTTOM

POSITIVEBUOYANCY

NEUTRALBUOYANCY

NEGATIVEBUOYANCY

Depth Control Tanks

Main BallastTanks

andMBTs


The ballast tanks in a submarine are of two kinds: main ballast tanks (MBTs) and depth control tanks (DCTs). MBTs tend to be entirely filled with water when the submarine submerges and to be entirely filled with air when it surfaces. In contrast, DCTs are partially filled with water, and the water level in the DCTs is controlled to change the depth. If the density of the water outside the submarine changes (this happens due to temperature or salinity changes), it is the water level in the DCTs that is adjusted to maintain the submarine at a constant depth.Water may also be moved from one tank to another to change the orientation of the submarine with reference to the horizontal (its ‘trim’). This is performed using pumps.In practice, a fully submerged submarine is in an unstable equilibrium and tends to either float or sink. So the DCTs need to be operated continually.

water pressures. Compressed air at pressures greater than these water pressures is used to push out the water in the tanks.

A submerged submarine must therefore carry sufficient compressed air at a sufficiently high pressure to de-ballast its tanks and return to the surface.

Other uses of compressed air on board a submarine are no less critical. At times submarines operate submerged and at the same time take in air from above the surface. This permits them to operate on diesel engines (which require a continuous

supply of air), the advantage being that they can cover long distances; if they run on electric motors, apart from having a lower ‘endurance’, they also have lower speeds. To take in air (known in the parlance as ‘snorting’), submarines use a device known as a snorkel. This is essentially pipe-like and is raised like a periscope. Snorkels are provided with automatic valves to prevent seawater from being drawn in when it washes over them. Compressed air is essential for the operation of these valves.

Indeed, in some submarines, the valves of the ballast tanks are also pneumatically operated.

The engines of a submarine are so large that compressed air is required to crank them when they are started (see also An Interesting Role in Elgi Magazine, volume 3, April 2007–March 2008).

Compressed air finds a number of other uses on board a submarine: in the firefighting system; in the water supply system of the vessel; and in the relatively commonplace application of driving pneumatic tools.

Naturally, a submarine has on-board compressors and an elaborate compressed air supply system. Given that the risks involved in the near-

A SUBMERGED SUBMARINE MUST THEREFORE CARRY SUFFICIENT COMPRESSED AIR AT A SUFFICIENTLY HIGH PRESSURE TO DE-BALLAST ITS TANKS AND RETURN TO THE SURFACE


isolated world of the submarine cannot be overstated, this system is built to extraordinary specifications. All precautions are taken, particularly to prevent corrosion: (a) The dewpoint of the air is exceptionally low, (b) the valves are ground to close tolerances, (c) the pipes supplying compressed air are made of titanium, and (d) the inner surfaces of the pipes are given a mirror finish to discourage condensation, which is a potential source of pitting.

In addition, each submarine carries a bank of compressed air bottles holding air at 300 atmospheres or so. Some of these bottles are reserved for emergencies—they will be used only for de-ballasting.

Use of the on-board compressors to fill the bottles (during snorting time) is avoided so that these machines experience less wear (and are therefore more reliable). The bottles are filled using an on-shore compressor when the submarine comes to the dockyard. And considering the application, it is not surprising that the on-shore compressors are designed and certified to work under particularly exacting conditions. They need to work in the extreme conditions found along the coast, including ambient temperatures of 45 degrees Celsius and a corrosive environment.

The requirements relating to the quality of air are particularly stringent. The air delivered by the compressor needs to be extremely pure, and practically all dust, oil and moisture must be removed. The purity with respect to humidity is specified in terms of the dewpoint. Whereas the dewpoint is -40 degrees Celsius in typical industrial applications, for submarine use, the dewpoint must be -55 degrees Celsius. The machine must deliver air at a pressure of 300 to 350 bar. It should be possible to tow it to any location along the dock, and there should be a provision to lift it using a crane.

Elgi Sauer has designed HURRICANE series compressors for these dockyard requirements and has begun supplying these machines. These four-stage reciprocating compressors have the cylinders arranged in a circular layout. They are trolley mounted and have weather-proof canopies. These compressors

are electrically driven, and they are provided with 50 metre power cables connecting them to the mains. The compressed air is delivered through a hose, also 50 metres long. Both the cable and hose are wound on drums.

The machines feature an inter-stage moisture separator, and a de-mister is provided to remove oil and water from the compressed air. The air from the de-mister is cooled to less than 60 degrees Celsius and passed through a desiccant dryer for removal of remnant moisture. These compressors also have a number of features to ensure safety. They are provided with anti-vibration mounts that protect the machines during transport and prevent vibrations from being transmitted to the surroundings during operation.

The dockyard compressed air systems are built for easy mobility and are very stable. They have been aesthetically designed.

THESE FOUR-STAGE RECIPROCATING COMPRESSORS HAVE THE CYLINDERS ARRANGED IN A CIRCULAR LAYOUT. THEY ARE TROLLEY MOUNTED AND HAVE WEATHER-PROOF CANOPIES.


DEEP WATER,

ELGI COMPRESSORS IN THE EXTRACTION OF FOSSIL FUELS

FAR FROM LAND


DEEP WATER,

The human world consumes fossil fuels with an appetite that is well beyond the limits of

seemliness. This is so well known that one hardly needs to furnish statistics to substantiate the statement. But consider oil alone (apart from gas): we consume some 80 million barrels of it each day, with a ‘barrel’ being nearly 160 litres. The thought that consumption at this level has been going for years or decades is staggering. It is also astonishing that so much petroleum has accumulated within the earth as a result of the breaking down of the remains of tiny organisms that have dropped to the sea floor.

But it is hardly surprising that, given the gargantuan craving for oil and gas, remarkable technologies have been developed for extracting these resources. Oil and gas are typically found at great depths below the Earth’s surface (most of the world’s petroleum is said to be trapped at depths ranging from 150 to 7600 metres below the surface), apparently impossible to reach, where temperatures and pressures are high. And with the proportions of land and sea on the earth’s surface being what they are, more of these resources are found below the sea. The demand for hydrocarbons is so great that even here, petroleum is not beyond the reach of humans—they have found it worthwhile to develop extreme technologies, expend resources on a very large scale and even put life at risk to extract these substances.

This article highlights a role that Elgi compressors play in the extraction of fossil fuels.

In the early days of prospecting for oil, locating deposits was simply a matter of looking for oil that leaked to the surface. As such deposits became increasingly difficult to find, other methods had to be employed. Once the process of formation of hydrocarbon deposits was understood, geographical signs were studied to locate anticlinal faults below the ground. When a potential oil reservoir was found, an exploratory well was drilled to confirm the presence of hydrocarbons.

Looking for deposits under the sea was rather more complicated, to say the

least. It became feasible mainly with the development of seismic methods. These are methods in which, to put things simply, explosions are set off at the surface and the shock waves reflecting off the rock layers below are studied. Much can be determined by placing listening devices (geophones on land, hydrophones at sea) at particular locations and determining the intensities of the returning shock waves and the durations after which they reach these locations.

Today prospecting for oil under the sea is a sophisticated affair. An array of compressed air cannons is used to produce the shock waves. These waves are powerful enough

The formation of oil and gas is believed to have begun when dead organisms sank to the bottom of the sea. It began long ago, in the geological period known as the Carboniferous (some 300 million years back). Over a period of time, layers of decaying creatures built up, and the remains got buried under deposits of silt and sand, forming a sludge. Millions of years passed, and these remains got buried deeper and deeper. Tremendous pressures and temperatures were developed. The heating of the sludge was anaerobic (it was not exposed to oxygen), and crude oil, natural gas and water were produced. Any rock containing all these materials is known as source rock.Natural gas and crude oil can migrate through porous rocks such as limestone. So hydrocarbons tend to keep moving until they encounter an impermeable layer of rock. They accumulate in traps (‘structural anticline traps’) where rocks have folded due to tectonic action, producing an arch or dome.

to penetrate 6000 metres below the surface. The recorded data are analysed using computers, and accurate three-dimensional images are generated. Whereas oil and gas cannot be seen, the structures that potentially hold them can be seen in these images. This prospecting is a bit like carrying out an ultrasonic examination of the earth, only it is rather more noisy.

Along with seismic surveys, other studies are carried out. For example,

Source: Wikipedia

FORMATION OF OIL AND GAS DEPOSITS BELOW THE SEA

WE CONSUME SOME 80 MILLION BARRELS OF IT EACH DAY, WITH A ‘BARREL’ BEING NEARLY 160 LITRES


cores are drilled and the samples obtained are examined. When the presence of oil and gas is confirmed, further core tests are conducted to assess the extent of the oilfield. The quality of the hydrocarbons and the amount of oil and gas present are also assessed.

Once a viable oilfield has been identified, the challenge is to drill in the dark depths of the ocean and transport the gas and oil to the surface. This must often be done under very rough weather conditions, and care must be taken to ensure that the ocean is not polluted.

It is to meet this challenge that oil offshore platforms are built. On average, a well is economically workable for 10 to 20 years. So platforms are built with long operations in mind. These offshore platforms have facilities for drilling oil wells and for extracting oil and gas from these wells. Platforms also have facilities for processing these materials and storing products before they are transported to land. Drilling may proceed at a large number of wells from a single platform. Drilling may be at an angle, and so the deposits that are tapped may be located kilometres away from a platform. Even after the wells have dried up, an offshore platform may continue to serve as a processing and storage hub for other oil platforms nearby.

There are different kinds of oil platforms—some of them float and are tethered to the seabed; others are built on under-sea towers rising hundreds of metres from the depths. As a rule, oil platforms are enormous structures—they have been described as ‘marvels of modern engineering’ and as ‘cities on the sea’. It has been pointed out that an oil and gas

platform may be as tall as a skyscraper and as broad as a sporting stadium.

Apart from drilling rigs and production facilities, the space on an offshore platform also has quarters for the crew. Hundreds of people may work on an oil platform. The personnel on a platform range from the installation manager (the ultimate

It may be pointed out that in the course of prospecting for oil, the extremely powerful sound waves used are sent into the sea every 10 seconds, for weeks at a time. The air cannon arrays are trailed behind vessels travelling at fixed speeds in predetermined survey patterns.It is possible that many living things are harmed or killed by exposure to these shock waves. Whales and dolphins, which depend on their sense of hearing to feed and communicate, may suffer permanent hearing damage. Once they cannot hear, they do not have a chance of surviving.Just how loud are air cannons? The maximum sound level within 500 metres of air cannons may be 180 decibels. In comparison, the sound level during normal human conversations is 60 decibels. Humans can undergo permanent hearing damage after even momentary exposure to sound levels of 140 decibels.

RATHER MORE NOISY

TYPES OFOFFSHOREPLATFORMS


authority on the platform) to crane operators, ballast control operators, dynamic positioning operators, scaffolders, maintenance technicians and production technologists. There is a catering crew and, if drilling operations are being performed, a drill crew. There may be a well services crew, including tubing operators.

Everyone on a platform is constantly engaged with two thoughts. One is about how to maintain the oil and gas production at the greatest rate. The industry works round the clock, seven days a week. This means that shifts are long—up to 12 hours long—and that there are night shifts.

The other preoccupation is safety. There are great risks associated with extracting highly inflammable substances. There is an ever-present risk of explosions. And accidents do occur, with loss of lives. Even otherwise, an offshore platform

is a hazardous place. Dangerous machinery is in operation, and work may have to be carried out at great heights regardless of the weather. A platform may even capsize in stormy weather.

Petroleum companies train their employees extensively to work safely on platforms. And they

PETROLEUM COMPANIES TRAIN THEIR EMPLOYEES EXTENSIVELY TO WORK SAFELY ON PLATFORMS. AND THEY PAY THEM HANDSOMELY.

pay them handsomely. A worker may earn a holiday of two weeks for every two weeks on the platform. The accommodation on the platform is comfortable, and food is available around the clock. There are recreational facilities on the platform, and computers connected to the Internet are available.

LIVINGQUARTERS

THEDERRICK

CRANE


MISTRAL & PASSATBut there are also unmanned platforms. These are smaller, satellite platforms that are designed to be operated remotely. Personnel are not present continuously on such platforms. They visit only once in a week or fortnight for supervision and maintenance. The machinery on a ‘normally unmanned installation’ runs automatically, and it is controlled remotely. Any faults are signaled to the main platform.

Among the machines on an unmanned oil and gas platform are air compressors. These compressors are run when personnel visit the platform for maintenance, and the compressed air is stored in bottles. When the maintenance staff leave the platform, the compressors are turned off. The stored air runs a range of applications, from instrumentation to valves and pumps, until the next visit.

MISTRAL and PASSAT series compressors from Elgi Sauer are used in unmanned platforms—at locations far from land, positioned high above water tens of metres deep. These are multi-stage reciprocating air compressors and have special features that make them suitable for installation and use on oil and gas platforms. For example, these compressors are mounted on portable box-type skids and are provided with sling-and-shackle arrangements so that they can be easily lifted using cranes. And all the electrical items of these machines are designed to meet the standards of classification societies.

AMONG THE MACHINES ON AN UNMANNED OIL AND GAS PLATFORM ARE AIR COMPRESSORS. THESE COMPRESSORS ARE RUN WHEN PERSONNEL VISIT THE PLATFORM FOR MAINTENANCE, AND THE COMPRESSED AIR IS STORED IN BOTTLES.


The heart is, as we know, a tireless organ—it is constantly pulsating because it pumps

blood as long there is life. So do the lungs too expand and collapse alternately all the time. The muscles involved in locomotion are, naturally, dynamic things, contracting and relaxing during movement. Even the eyes, fixed in sockets as they are, are energetic, darting hither and thither incessantly. These are all clearly active organs, exhibiting obvious signs of life. Somewhere towards the quieter end of the spectrum of activity you find the bones.

You may well conclude that there is nothing in the human body that is more dull and inert—nothing that is as, well, lifeless as a bone. In contrast with the pulsating heart, the heaving lungs or even the skin (breaking into a sweat when cooling is required, for instance), the bones appear rigid and inert. They are just unchanging building blocks that are within us. And they do nothing but get moved by muscles attached to them.

But such impressions are incorrect. As the moral of one of Aesop’s fables goes, appearances are often deceiving; bones are actually very active organs. They do change. And contrary to appearances, they are possessed

of elasticity, both figuratively and literally.The various functions of bones give an indication of just how dynamic these organs are.

A great many functionsMovement—of individual body parts or the entire body—is an obvious activity in which bones play an important role. The leverage that bones provide through their rigidity allows forces to be generated that produce motion. The advantages that the musculo-skeletal system confers for movement may be readily appreciated by comparing an animal with an internal skeleton (say a very small snake) and one without (such as an earthworm—a very large earthworm, for purposes of comparing similar-sized creatures).But bones have mechanical functions other than movement. They form a scaffolding, as it were, on which the human body is built. Imagine what we would look like if we did not have bones: Maybe we would be shapeless blobs, having the form of giant amoebas.

Bones also protect various organs such as the heart, lungs and brain.

Further, we have a set of three small bones in each ear that transmit and amplify the pressure changes

associated with sound. Thus these bones have a vital role in our perception of sound (see the article ‘All Ears’ in this issue of Elgi Magazine).

What are not obvious are the numerous metabolic functions that bones have. The term ‘metabolism’ is all-encompassing, referring to the entirety of chemical reactions involved in keeping cells and organisms in the living state.

Bones are great storehouses. They serve as reserves of elements that are important for the body, particularly phosphorus and calcium. They also store growth factors (substances—mostly proteins and hormones—that are involved in regulating various cellular processes and that may stimulate cellular growth). Some bones store fat as well. Bones can also remove and store toxic elements from the blood so that the effects of these elements on other tissues are reduced.

Bones are constantly absorbing or releasing alkaline salts, maintaining the acid–base balance and preventing excessive changes in the pH level of the blood.

Bones also control the metabolism of phosphates. They release a substance


HELPING BONES HEAL

known as FGF-23 (short for fibroblast growth factor–23), which reduces phosphate reabsorption by acting on the kidneys.

Bone cells produce a hormone called osteocalcin. This hormone has roles in regulating fat deposition and in regulating the level of glucose in blood.

Apart from all these functions, which are quite important by themselves, bones are responsible for producing blood. Blood cells are produced in bone marrow, which constitutes a surprising 4 percent of the total body mass of a human. It has been pointed out that a person weighing 65 kilograms, for example, has around 2.6 kilograms of bone marrow.

VarietyTalking of marrow brings us to the structure of bones. As even the most cursory of glances at the skeleton will reveal, not all bones are of the same shape or size. Depending on their shape, bones are broadly classified into different groups.

COMPRESSED AIR FINDS INNUMERABLE USES IN OUR LIFE TODAY. AS A RESULT, IN PRACTICALLY ANY FIELD, YOU ARE LIKELY TO

FIND MULTIPLE ROLES PLAYED BY COMPRESSED AIR. ONE USE IS MENTIONED AT THE END OF THIS ARTICLE. WE INVITE YOU TO

CONSIDER THE QUESTION ‘WHERE IS THE COMPRESSED AIR IN THIS STORY?’ AS YOU READ THE ARTICLE AND TO ANTICIPATE

THE APPLICATION BEFORE IT IS REVEALED.


Long bones are, as their name suggests, those bones that are considerably longer than they are wide. A number of bones of the limbs, such as the femur (thigh) and humerus (upper arm) are long bones. Short bones (examples are found in the ankle and wrist) are not only short—they are also roughly cube shaped.

Some bones are embedded within tendons. Such bones are known as sesamoid bones. The patella (knee) is a sesamoid bone. Others are found in the hand, wrist and foot.

Most bones of the skull are thin and curved. These are known as flat bones. The sternum (breastbone) is another flat bone.

And then there are irregular bones, with complex shapes—the bones of the pelvis and spine, for instance.

Bones, in these varied forms, have two kinds of tissue. Both these forms are composite structures, made up of rigid calcium compounds and more elastic collagen (a protein).

One of the two kinds of bone tissues is compact bone tissue, also referred

to as dense bone. This tissue has few spaces within it. Compact bone has a white and smooth appearance.

The other kind of bone tissue is cancellous bone, also known as spongy bone or trabecular bone. Cancellous bone is typically found in the interior of the bones of the spine and at the ends of long bones. It is weaker and more flexible than compact bone. Cancellous bone is well supplied with blood vessels.

Cancellous bone often contains red bone marrow, the form of marrow in which blood cells are produced. There is another form of marrow, yellow marrow, that is found in the hollow portion of long bones. Yellow marrow is mostly made up of fat

cells. Curiously, if there is a severe loss of blood, yellow marrow may be converted to red marrow to boost blood cell production.

As it happens, change is a significant theme in the things bones do.

ChangeThe skeleton is always being ‘remodelled’—that is to say, some of the constituent material is being transferred to blood and subsequently replaced. As a result of this ‘bone turnover’, a tenth of the entire mass of the skeleton is replaced each year although there is little change in the shapes of the bones.

Bones also adapt to the loads to which they are subjected. If the loads on a

IT HAS BEEN POINTED OUT THAT A PERSON WEIGHING 65 KILOGRAMS, FOR EXAMPLE, HAS AROUND 2.6 KILOGRAMS OF BONE MARROW.

BONESTYPE OF


particular bone are increased, over time that bone grows stronger to withstand that type of loading. The reverse is also true. If the loading of a bone is reduced, it grows weaker. Thus if there is increased physical activity, bone grows stronger (by growing thicker at the points of maximum stress), and if there is no loading (as in bed rest or space travel), it grows weaker. This was formally stated by a German surgeon, Julius Wolff, in the 19th century, and thus we have Wolff’s law:

Every change in the function of a bone is followed by certain definite changes in its internal architecture and its external conformation.

When the loading is optimal, the bone gets hypertrophied, that is, its bulk and strength develop greatly. But loading beyond the tolerance of the bone results in stress fractures, wherein the bone fails. Stress fractures happen commonly in fresh army and police recruits.

Above all, there is perhaps no better indication of the living, responsive nature of bones than the fact that they heal themselves. No manmade machines can repair themselves after damage in the way living things recover after an injury. Bones are said to be genetically programmed to heal after fracture. At first the collagen fibres are randomly oriented, and so the newly formed bone is called woven bone. Soon the woven bone is replaced by lamellar bone, which is more organised. The collagen fibres are found in layers in lamellar bone, with the fibres in each layer being parallel.

StabilisationBroken bones may need to be aligned first through traction, which is the application of a pulling force. Then, to heal, they need to be ‘stabilised’—as is obvious, there should be no relative movement between the broken parts of a bone for restoration to take place.

However, micro movements between the fragments actually help the healing of fractures such as collar bone fractures and rib fractures.

Historically, the treatment of fractures involved restriction of activity and bed rest. A more practical method was to use splints, or rigid strips.

The use of bandages stiffened with various materials was also practiced. Over the ages, resins, starch, wax and parchment have all been used to stiffen bandages.

The use of plaster of Paris casts, perhaps the best known treatment for fractures, was apparently introduced in Europe only in the 19th century. Plaster of Paris casts continue to be used to the present day, but they have some disadvantages. They are quite heavy, and so they can restrict

movement considerably. They can also cause cutaneous complications. Lighter casts made of fibreglass, with waterproof liners, are now available. Patients can even bathe and shower with these casts. But doctors have developed, and have been using for many years, a variety of other ways of healing fractures.

Plates, screws, nailsA fractured bone may be broken in a number of ways (transversely, obliquely, fragmented and so forth).

REPAIR OF FRACTURES

BONES ALSO ADAPT TO THE LOADS TO WHICH THEY ARE SUBJECTED. IF THE LOADS ON A PARTICULAR BONE ARE INCREASED, OVER TIME THAT BONE GROWS STRONGER TO WITHSTAND THAT TYPE OF LOADING.


The use of intramedullary nails began in 1858, when the technique was used in Norway to treat a fracture of the neck of the femur. A problem of corrosion was faced with the early nails. Materials used today are chosen so as to avoid this problem and for biocompatibility. Usually an intermedullary nail can remain inside a bone for ever.

Medical opinion on the merits of removal of implants and nails appears to be divided. There can be complications in removing implants, particularly when these are deep and have been in place for a long time.

Depending on the particular bone or bones affected, the age of the patient and the extent of damage to the surrounding soft tissues, the doctor chooses an appropriate method of treatment.

External fixation. This method may be used in instances (among others) of severe open fractures and closed fractures in which there is severe injury to the soft tissues. A tube, rod, circular device or other arrangement made of metal provides the support to the broken parts of the bone. This rod or other device is outside the body, and it is linked to the bone by implants. These implants are typically special screws, and they extend from the external plate or rod through the skin and soft tissue into the bone. Holes are drilled in uninjured areas of the bone to fasten the screws as though it were so much metal or wood.

Naturally, the procedure is carried out under anaesthesia. Healing of a fracture may take from 6 weeks to many months. The screws and the external frame are removed after healing is complete. Removal usually does not require anaesthesia.

Implants. The fractured bone may be stabilised using a metal plate that is inserted into the body surgically. Plates were first used for stabilising bones in Germany in 1886. These were made of German silver, an alloy of nickel, copper and tin. The use of plates has progressively developed over the years. The plates are available in standard formats. They may also be contoured specifically so as to match the natural shape of the outer surface of the bone involved and to hold the broken parts together with a compressive force. Plates are usually made of titanium or stainless steel. The screws come in some standard diameters, and their lengths are chosen as required for each position. Threads may be tapped into the bone for fixing the screws; alternately, the screws may be self-tapping screws.

Bones may need to be aligned (‘reduced’) during the surgery before a plate is fixed. This alignment is referred to as ‘open reduction’. In many cases the implants are left inside the body. Implants may need to be removed, however, if they cause irritation to surrounding tissues, as happens at times.

Intramedullary nailing. This technique is typically used to treat fractures of long bones such as those of the arm and leg. In this method, a ‘nail’, a specially designed rod, is inserted through the hollow (marrow) space in the middle of the bone.

WHERE IS THE COMPRESSED AIR?Compressed air is used in the process of producing the stainless steel implants. These plates are machined in a CNC machine. When the cutter of the machine removes metal as it shapes the stainless steel form, minute chips are generated that get deposited on the workpiece. Air at high pressure is directed over the plate to remove the tiny chips and dust and obtain an implant that is free of burrs.Compressed air also drives the pneumatic tools used during surgery. Further, hydroxyapatite coatings may be applied on implants using compressed air.

THE USE OF INTRAMEDULLARY NAILS BEGAN IN 1858, WHEN THE TECHNIQUE WAS USED IN NORWAY TO TREAT A FRACTURE OF THE NECK OF THE FEMUR.

PICS: Dr. A. Chandrasekaran, orthopaedic surgeon, Chennai


NEW PRODUCTS

Breathing Air CompressorElgi Sauer has designed and tested a compressor to deliver breathing air. This compressor was developed in collaboration with the Greek manufacturer Paramina, and it is to be launched shortly.

Breathing air compressors deliver air at high pressures and are used in scuba diving and fire fighting applications and in general in situations where humans work in contaminated air spaces. A breathing air compressor must deliver air that is free of all potentially dangerous contaminants such as oil vapours, rust, moisture and gaseous hydrocarbons.

The new compressor delivers air at 300 bar and an outlet air temperature of 41 degrees Celsius. The calculated free air delivery (FAD) of the machine is 4.2 cfm. Its overall dimensions are 1140 mm (length) × 480 mm (breadth) × 690 mm (height), and it weighs 126 kg.

Natural Gas CompressorsThe Hurricane series reciprocating compressors from Elgi Sauer are designed for boosting the pressure of natural gas or biogas (methane produced from organic material using microbes).

Biogas can be produced from agricultural byproducts and waste using systems known as anaerobic digesters. Compressing biogas or natural gas to high pressures makes it easier to transport the gas from the point of production to consumers.

Since the gas is highly inflammable, the motors and valves used in the gas compressors are flameproof. The compressors are gas-tight. No leak is permissible as the gas is also toxic. The piston and cylinder are made of special-grade material.

Hurricane compressors are available in three models: WP4331, WP4341 and WP4351. They deliver gas at 300 bar, with their capacities ranging from 38.5 to 121.5 cfm and their power requirements ranging from 14 to 37 kW. The suction pressure is a minimum of 200 mbar. These air-cooled machines compress gas in four stages.


Prospot i4Inverter-based spot weldersTraditionally, transformer-based welding machines have been used for spot welding. The introduction of new-generation high-strength steels has stretched these machines beyond the limits of their welding power. Transformer-based welding machines also tend to overheat because of the low duty cycles of spot welding. This affects the quality of the welds.

Globally, automotive aftermarket body shops have moved to inverter-based spot welding machines. These spot welders have higher welding power compared with transformer-based machines. The new-generation welding machines consume less power and can be used to efficiently weld both new-generation steels and normal steels.

ATS ELGI offers the Prospot i4 to tackle all spot welding jobs. The Prospot i4 has features that spell convenience, efficiency and high productivity:• A dual-amp setting that makes it easy to weld high tensile steels

with low welding currents• High welding power• Low power consumption—reduced costs• High duty cycles—improved weld quality and increased

productivity• Water-cooled spot guns for greater productivity• Self-aligning electrodes with easy-to-change C arms• A variety of extension arms that reach inaccessible parts• Data log for managing and tracking weld history• Large LCD displayThe Prospot i4 alerts the operator about the quality of each spot (whether it may be approved or rejected), thereby ensuring quality.

Synergic 176The Synergic 176 is another product from ATS ELGI that uses inverters in place of transformers.

In gas metal arc welding (GMAW), as with spot welding, there is a shift to the use of inverter-based welders. With their advantages of high welding power and low power consumption, inverter-based welding machines are smaller and lighter than equivalent transformer-based machines.

The welding parameters are automatically set by the Synergic 176. This lightweight and compact welding machine has a high-quality torch for a perfect finish. The Synergic 176 has a control for fine-tuning the arc length. This welding machine supports wire reels weighing up to 5 kilograms and having a diameter of up to 300 millimetres. A wire feeder unit and cylinder stand are standard fittings. A power factor correction feature has been built into the Synergic 176. The result of these features is a high-quality weld.


SMART DRYThere is a definite drift in automotive applications from the use of solvent-borne paints to water-borne paints. Water-borne paints have reduced volatile organic compound (VOC) emissions, but their drying times are longer compared with solvent-based paints.

ATS ELGI’s Smart Dry reduces the drying times of water-borne paints by creating a turbulent air flow above a painted surfaces. The turbulent flow quickens the drying process by disrupting the slow-moving boundary layer adjacent to the painted surface.

The Smart Dry can be integrated with all paint booth models. It has a certified flameproof motor. It has 10-micron pocket filters. The doors of the Smart Dry open and close automatically. The power consumption is low—each Smart Dry tower consumes only 0.25 kilowatts.The use of Smart Dry gives a better finish.

PREP KINGThe Prep King is a prep station—it is used for carrying out all preparatory work before painting. Even minor paint jobs can be carried out inside this specially designed preparatory booth. It has walls on three sides and a PVC curtain of a flameproof material. An integral drive-on ramp is provided to reduce the installation space.

A downdraft is produced in the drying and painting modes. Filters are provided on the ceiling and base. The Prep King also has a pre-filter and a pocket filter. During drying, the air is subjected to three levels of filtration before it is let out, and during painting there is a four-level filtration. The multiple stages of filtration ensure that pollution is controlled. Further, it needs less exhaust ducting, which translates to a lower cost to the customer.

The Prep King features a pneumatically operated automatic dampener control which makes it suitable for minor paint jobs. This feature ensures quick repairs, thus increasing the productivity. Among the other features of the Prep King is an emergency stop switch.

NEW PRODUCTS

the elgi magazine 1 10 apr 2015 - mar 2016 ... the elgi magazine 7 ... the joys of the cruise have a...

Documents