basic maintenance aspect

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CONTENTS

SI. NO. DESCRIPTION PAGE NOs.

1. ENGINEERING MATERIAL 1

2. BASIC SCAFFOLD CONTRUCTION 20

3. SLINGING METHODS 36

4. PRINCIPLES OF CORRECT HANDLING AND LIFTING 67

5. MEASURING INSTRUMENTS AND GAUGES 91

6. COUPLINGS 115

7. ALIGNMENT 147

8. REALIABILITY ANALYSIS 156

9. PERMIT TO WORK SYSTEM 180

10.IMPROVING POWER PLANT AVAILABILITYWITH SPECIAL

REFERENCE TO MAINTENANCE183


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1 Engineering MaterialsMETALS

Metals are distinguished from non-metals by their lustre and greater density. In the polished

condition all metallic elements are white, except copper, which is reddish, and gold, which is

yellow.

Few metals are used in the pure state, but are melted together with one or more other metals to

form alloys. This alloying is carried out to give the resulting metal certain desirable properties

such as greater strength, hardness, or increased resistance to corrosion. The proportions of the

various alloying elements are of great importance as slight variation can alter completely the

characteristics of an alloy. The alloying additions need not be metals; carbon and silicon are

added to steel, and sulphur is also found in ferrous alloys although it usually occurs as an

undesirable impurity.

Metals are usually divided into ferrous and non-ferrous metals. Ferrous metals are those

containing and consisting mainly of iron, whilst non-ferrous metals contain little or no iron.

FERROUS METALS

The ferrous metals are outstanding for their mechanical strength and rigidity. Cast iron is very

strong in compression and can be cast into intricate shapes. It is used for machine beds,

columns, cylinder heads, and has countless other used. A further useful property is that a piece

of cast iron will slide over another piece without seizing. This is due to the presence of tiny

flakes of graphite which lubricate the sliding surfaces. This property is used to advantage in

machine tools, for example, the cast iron slide and saddles on a lather.

PLAIN CARBON STEELS

Plain carbon steels are used for all types of constructional work, from girders in bridge building

to tiny nuts and bolts in instruments. Plain carbon steel with a carbon content of between 0.4


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and 1.4 percent can be hardened by heating to a cherry red and quenching in oil or water. This

enables these higher carbon steels to be employed for cutting tools such as chisels and files.

ALLOY STEELS

There are a great many alloy steels each having special advantages. Some possess very high

strength or resistance to corrosion, whiles other retain their strength at high temperature or

possess exceptional hardness and resistance to abrasion.

Note:

Nearly all ferrous metals are magnetic, the exceptions being stainless and highly alloyed steels.

A magnetic material is one which is able to attract, or be attracted by, a magnet, and itself

capable of being magnetised.

NON-FERROUS METALS

In the pure state the non-ferrous metals are al mechanically weaker than the ferrous metals, but

they possess several important advantages.

Under most conditions their resistance to corrosion is good; lead, tin, chromium and zinc are all

used to give protective coatings to steel to prevent it from rusting away.

Copper and aluminum are very ductile metals and can easily be worked into such forms as wire,

tube and sheet in the cold state.

A wide variety of alloys can be obtained by different combinations of non-ferrous metals. Brass

and bronze are made by alloying copper with zinc or tin respectively; the resulting alloys are

much stronger than their constituent elements.

BLACK MILD STEEL

Black mild steel bar is a common rolling mill product. It may be obtained in round, square,


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rectangular and hexagonal sections. Round bar from 1/4 diameter to 10 diameter; rectangular

bar from 1/4" x 1/8" to 2 x 12, square and hexagonal from small sizes upto 6 across are

typical ranges. The surface of black scale is due to oxidizing of the steel by the atmosphere

during hot rolling. Generally, the corners of all black bar are slightly rounded.

BRIGHT MILD STEEL

Is obtained by cold drawing mild steel bar through shaped dies; the finish is smooth, and in

sections other than round; the corners are sharp. The size and shape may be guaranteed within

0.002 in. This accurate size and bright finish are often a great advantage. Capstan, turret and

automatic lathes are sometimes fitted with a collect chuck which feeds the bar forward as

required; this is self-centering chuck, and can be used only with accurate round bar stock. The

drawing operation work hardens the surface of bright drawn bar, the depth of this hardening

depending on the severity of the drawing.

CAST IRON

Carbon is the most important alloying element in iron and steel. In cast iron, which is the general

name for iron re-cast from pig iron, carbon is present in two forms; as free carbon or graphite;

and as combined carbon or iron carbide. The graphite is in the form of flakes which impart the

graphite is also responsible for the brittleness of cast iron and its dirtness when being

machined or filed. The graphite flakes are discontinuities in the structure; they are a source of

weakness if tensile forces are applied, but have little effect on the compressive strength of cast

iron, which is quite good. The small cavities containing graphite have a damping effect on

vibrations. Graphite is an excellent lubricant, and grey cast iron is easily machined, as the tool is

lubricated and the chips break off readily. The freedom with which articles will slide over a

smooth surface of cast iron is largely due to the graphite in the surface.

Although there is a tendency today to replace iron castings by mild-steel welded structures, cast

iron is still one of the commonest engineering materials. It can be cast into intricate shapes, and

is equally useful for one-offs to a wooden pattern, or for mechanical moulding with metal

patterns in mass production foundries. Cast iron is used in construction of machine tools, lathe

beds, etc.


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COPPER

Pure copper is a soft ductile metal of high electrical conductivity. The best quality of copper for

wires and other electrical conductors contains only faint traces of other elements. It is termed

electrolytic copper, from the method of refining. Best select copper is less pure and has a lower

conductivity but is cheaper and finds many uses. Arsenical copper has upto 0.5% arsenic and

smaller amounts of other elements; it is stronger than pure copper, and is used for heater tubes,

rivets, etc. Copper is resistant to a number of corrosive liquids, and is used in chemical works,

food and brewing plants; its ductivity allows heavy cold work, and sheet copper is spun, pressed

and drawn into many shapes.

BRONZE

The simplest type of bronze is an alloy of copper and tin. Bronze containing 95% copper and

5% tin is very ductile, but work hardens more rapidly than 70/30 brass. The tin content of simple

bronzes oxidizes very quickly when the metal is hot, forming tin oxide. This makes the bronze

brittle and scratchy. Various deoxidizers are added, the most common being zinc or

phosphorus.

PHOSPHOR BRONZE

Phosphor bronzes with a tin content of 10%, 13% and 0.5% - 1.0% phosphorus, with the

remainder copper, are used for heavy duty bearings. They have a low coefficient of friction,

great hardness and an excellent resistance to wear, together with very good resistance to

corrosion by sea-water.

ALUMINUM

Aluminum is a white metal which is processed from the oxide (alumina) which is prepared from

a clayey mineral called Bauxite. Pure aluminum is a weak but ductile metal, its most important

property is its light weight roughly one third that of iron.


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Aluminum mixed with other alloys in small amounts will become hard and rigid, aluminum itself

is very ductile and malleable. It can be rolled into leaf about 0.025mm thick and drawn into wire

about 0.10mm dia. A high finish can be obtained by burnishing and polishing. It has a very good

electrical conductivity, lending itself to be used for overhead cable as in the grid system pylons.

Owing to a thin layer of oxide which covers its surface it has a high resistance to corrosion

which makes it a useful metal for cooking pans.

Aluminum foil is used for wrapping chocolates, cigarettes and for sealing milk bottles.

Powdered metal is used as the base for aluminum paint.

TYPE OF STEEL FORM OF SUPPLY CARBON % USE AND PROPERTIES

Dead Mild Black and Bright 0.07-0.15 Pipes, Chains, Rivets, Screws,or Bar, and Tube Boiler Plates.Low Carbon and wire

Easily worked when hot,Difficult to machine owing toTendency to tear.

-------------------------------------------------------------------------------------------------------------------------------Black Bar Section 0.15-0.25 Ship Plates and Forgings,

Mild and Sheet Bright Gears, Shafts, Nuts and Bolts,Strip, Tubes and Rivets, Chains.

Forgings Easily machined and weldedAnd is cheapest steel-------------------------------------------------------------------------------------------------------------------------------

Black Bar Sheet 0.25-0.5 Machine parts and forgings,Medium Sections and Castings, Springs, Drop

Plate Hammer Dies.Bright Bar, Rod, Responds to heat treatment

Carbon Flat, Strip and and can be machinedForgings. satisfactorily.

-------------------------------------------------------------------------------------------------------------------------------Black Bar and 0.5-0.7 Hammers, Sledges, Stamping

High Strip and Pressing Dies, Drop-

Forging Dies, Screwdrivers,Set-Screws.

0.7-0.8 Punches, cold Chisels,Hammers, Shear Blades,Drop-Forging Dies LatheCentres, Spanners, BandSaws, Rivet Sets, Vice Jaws


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Silver Steel 0.8-1.0 Punches, Rivet Sets, ScrewerDies, Screwing Taps, ShearBlades, Drop-Forging Dies,Saws, Hammers, Cold Chisels,Springs, Axes, Rock Drills,

Milling Cutters.

Carbon Rod 1.0-1.5 Drills, Milling Cutters, LatheTool Files, Saw Blades, BallBearings, Wi Drawing Dies,Screwing Dies, Taps

BRASS

This is an alloy of copper and zinc. It has a wide range of properties and uses.

Usually available in bar form for automatic and capstan lathes or as sheet and strip to be cut

into blanks for press work. Castings are of course, available to special order. Any cold working

of brass will tend to harden it, so before any subsequent operations can be carried out it is

nearly always necessary to anneal the brass by heating to about 500OC and quenching in water.

Brass may be sub-divided into 3 main groups, depending upon the zinc content.

1. The Alpha Brasses contain up to 39% Zinc.

They are extremely malleable and may be cold rolled into sheets, drawn into tubes, wire

and rod and used for cold stamping.

The best combination of tensile strength and ductility is found in cartridge brass which

is used for cartridge cases and condenser tubes. Although Alpha brass may be severely

cold worked, it is hot-short i.e. it tends to crack and disintegrate at high temperature.

2. The Alpha-Beta Brasses contain 39% - 46% Zinc. The most common brass in this

group in MUNTZ METAL which has a high corrosion resistance, is readily hot worked

and is used for extrusions, hot stampings, and for rolling into sheets and rods.

Bolts, pins and spindles are manufactured from bar and pump components are

frequently made from this metal. Stresses may be set up during casting, resulting in


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considerable distortion when machining occurs. The remedy being an annealing process

at 600 650OC carried out prior to machining.

These brasses are rather difficult to machine, but this can be remedied by the addition of

up to 3% lead in the composition of the metal. It can be cold worked only to a limited

extent.

3. Beta-Brasscontains 46% - 49% Zinc

Is used a lot in marine engineering due to its excellent corrosion resistance. It has a

tensile strength of 25-30 tons/in 2 and a low ductility, but it cannot be cold worked

without possibility of fracture. It is primarily a hot working metal. Above 49% zinc, the

alloys are very hard, but are so brittle that they are useless for most engineering

purposes. An exception to this is brazing brass with 50% zinc which is used because of

its comparatively low melting point.

GUNMETAL

This is a bronze with 2% zinc and was once used to product artillery, hence the name.

The zinc helps to produce sounder castings as it increases the fluidity of the bronze

counteracting the effect of the lead which is sometimes added to improve mach inability. It also

finds many uses in marine engineering and for steam plant work. Improved properties can be

obtained by an annealing process of about 700OC.

MATERIAL PROPERTIES

DUCTILITY

A ductile material can be drawn out without fracture into rod wire or tube by a tensile force. A

ductile material must possess a fair degree of tensile strength or it will break if an attempt is

made to draw it. Copper, mild steel and aluminium are ductile metals.


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MALLEABILITY

A malleable material can be hammered or rolled into shape without fracture as in forging and

hot-rolling of steel sections. Wrought iron and mild steel are malleable, especially when worked

at a bright red heat. A malleable material extends in more than one direction under compressive

forces.

ELASTICITY

If an elastic material is deformed by a force it springs back to its original shape when the force is

removed. This is known as the elastic limit of the material.

PLASTICITY

This is the opposite of elasticity. A plastic material can be easily deformed in any direction

without rupture by a force and will retain its new shape when the force ceases to act Putty is an

example of a plastic material. Plasticity of metals is increased by heating and the majority of

them can be hot worked.

BRITTLENESS

A brittle material breaks easily when subject to a sudden blow. Engineers have little use for

brittle metals but it must be appreciated that hardness is often accomplished only at the

expense of brittleness, and this means that the cutting tools used in engineering must be

handled with care.

FUNCTIONAL PROPERTIES

HARDNESS

Hardness is the ability to withstand wear and abrasion. The harder the greater the resistance to

scratching and indentation. The hardness of two materials can be compared by finding which


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will scratch the other. A diamond will cut glass because it is much harder.

TOUGHNESS

A tough material can resist repeated blow without fracture. Toughness depends on both the

strength and ductility of the material. Small hand tools drifts, chisels, etc must be tough to stand

up on the rough treatment they receive in use.

NON-FERROUS ALLOYS

BRASSES

---------------------------------------------------------------------------------------------------------------------

Copper Tin Properties and Uses

---------------------------------------------------------------------------------------------------------------------

85 15 Gilding metal-cheap jewelry

---------------------------------------------------------------------------------------------------------------------

75 25 Brazing brass-used where parts are to be

brazed or silver soldered.

---------------------------------------------------------------------------------------------------------------------60

40 Muntz metal-General range of articles e.g.

Water fittings, household articles, etc.

---------------------------------------------------------------------------------------------------------------------

PHOSPHOR BRONZE

---------------------------------------------------------------------------------------------------------------------

Copper Tin Phosphorus Properties and Uses

---------------------------------------------------------------------------------------------------------------------

95.7 6 0.3 Obtained as rod sheet and wire. When severely

cold worked (wire drawing) Used for springs.

---------------------------------------------------------------------------------------------------------------------

88.7 11 0.3 Castings and bearings

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WHITE METAL BEARINGS

---------------------------------------------------------------------------------------------------------------------

Tin Antimony Copper Lead Properties and Uses

---------------------------------------------------------------------------------------------------------------------

93 3.5 3.5 -- Motor car bearings (big ends)

---------------------------------------------------------------------------------------------------------------------

60 10 1.5 28.5 Engines, electrical machines and

ways

---------------------------------------------------------------------------------------------------------------------

There are just a cross-section of a great many alloys and their uses.


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ENGINEERING MATERIALS

Metals Non-Metals-------------------------------------------- ----------------------------------------------------Ferrous Non-Ferrous Plastics Miscellaneous

Copper

Wrought iron Aluminium Cellulose Rubber

Cast Irons Zinc Vinyl Resins Asbestos

Carbon Steels Lead Nylon Wood

Alloy Steels Tin Polythene MicaCadmium Shellac Ceramics

Brass Carbon

Bronze Stone

White Metals Bricks

Solders Concrete

PLASTICS

A plastic is a material which is capable of flowing under suitable conditions to assume a new

shape when the conditions are removed.

There are two main groups of plastics.

1. Thermoplastic materials

2. Thermo-setting plastics

1. THERMOPLASTIC MATERIALS WHICH SOFTEN AT 60OC.

Those can be softened and caused to flow an indefinite number of times by the application of

heat and pressure, provided that heat is not sufficient to cause chemical decomposition of the

plastics.


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They are available in form of sheets, rods, tubes and moulding powders; they are tough, easily

machined and have varying degrees of rigidity, they behave like ductile materials.

TYPICAL USES

Car handles, machine housings, valves, gears, hinges, bushes, kitchen ware.

Example

POLYTHENE

A wax like material that is chemically inert to most liquids. Very tough and slightly eastics. Good

insulating material used for moulded containers; tensile strength is 144.5 Mn/m2.

P.V.C. (POLY VINYL-CHLORIDE)

A tough rubber like material which is practically non-inflammable cheap plastic. Used as

insulating cover on electric cables.

Available in flat sheets at a thickness from about 0.005mm. (46.5-62 Mn/m2

).

PERPEX

Good substitute for glass used for electrical insulation purposes; can be bent, cut or machined,

unaffected by dilute acids, tends to be brittle.

NYLON

Tough and has a low co-efficient or friction with itself and polished steel. Can be moulded, used

for gear wheels, bushes, and bearings.

Strength is maintained to 204OC melting point, at low speeds no lubrication needed, but at high

speeds lubricants can be used.


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POLYSTYRENE

Flow readily at 180OC; used for injection moulding, rather brittle, good insulating material, used

for wall tiles, light fittings, toys, T.V. components, tensile strength 46.5 Mn/m2.

2. THERMO-SETTING PLASTICS WHICH SOFTEN ABOVE

Undergo chemical changes during the initial process of being shaped, and thereafter further

heat and pressure do not affect the shape, provided that he temperature does not reach the

decomposition temperature. Suitable for higher temperature applications than thermo-plastic

materials.

The moulding powder or resin may be shaped by compassion moulds or may be used to bond

together layers of paper or cloth, when compressed under heat, this forms rigid flat sheets or

other required shapes, similar to wood but have a better resistance to water.

BAKELITE

The resin is mixed with a filler of non-plastic material which is added as a powder or in a

fibrous state, so called wood flour filled give more brittle mouldings which crack readily under

shock loads or impact.

Cotton or shredded fabric fillers give tougher mouldings whilst asbestos can be used to produce

heat-resistant mouldings.

Tensile strength is 46.5 Mn/m2

Compressive strength is 154.5 Mn/m2

LAMINATE(TUFNOL)

Sheets of fibrous material are bonded in a solid mass by the thermo-setting, resin surface is

usually polished, generally combine good electrical resistance with mechanical strength, used in

building industry, table tops. Very brittle if used in unsupported thin sections.


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SILICON-PLASTICS-SILICONS

Differ from many other plastics in having silicon and oxygen as their base, with carbon and

hydrogen attached.

One important use is as an additive to oils, waxes, rubbers etc. Silicons are water repellant and

can withstand high temperatures. Very good for high temperature electrical insulation

applications.

Although plastics are replacing metals in many applications, this does not mena that they have

similar physical properties. Generally they do give a neater and cheaper product.

Plastics have excellent corrosion resistance but the correct type of plastics must be used for a

specific need, e.g. chemical plant work, pipes and storage vessels. If tensile strength is

required, laminated and reinforced plastics should be used, heat resitance is poor; they will

soften at approx. 100OC.

Special heat resistant plastics only soften at about 230OC, they tend to become brittle when

cold. They are poor conductors of heat and electricity, for this reason they are used for electrical

fittings.

HEAT TREATMENT OF STEELS

When iron is heated for room temperature it is observed that the temperature rise, after

proceeding steadily is suddenly arrested, and for a time the metal remains at practically the

same temperature even through the metal absorbs heat, the heat brings about certain changes

in the metal instead of raising the temperature. After the change is complete further heating

causes a rise in temperature as before the temperatures at which these changes occur are

termed arrest or critical points.

Critical points also occur in steel, but the temperature at which they occur alter with the carbon

content of the steel, in mild there are four critical points.


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The steel is now at its softest and most ductile state and can be suitable for most types of work,

hot or cold.

Normal Structure After cold worked

NORMALISING

This condition arises after a steel has been heated to slightly above the upper critical point and

then allowed to cool at room temperature.

The steel will be stronger and harder than that of annealed steel, but it does not lend itself to be

cold worked as easily.

Hot rolled plates, sections and forgings are worked whilst the steel is in the upper critical state

and then allowed to cool in about room temperature.

The method of normalising is cheaper and quicker than that on annealing but the cooling rate

cannot be regulated as carefully.

TEMPERING

Cutting tools made from fully hardened high-carbon steel are extremely hard, but are too brittle

to be of any use. Some of this brittleness, which is due to internal stresses set up by drastic

cooling, may be removed by suitable tempering. The shock resistance of the tool will be

increased considerably, whilst the harness will be lowered very little.

Cutting tools are tempered by heating to some temperature between 220OC and 320 OC, and

then cooling off. The high the temperature, the better will be the shock resistance, but the lower


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the hardness, the usual practice is to use the lower temperature for smoth-cutting tools so as to

retain the cutting edge as long as possible, whilst cold chisels and similar tools are tempered at

the higher temperatures to give good shock resistance.

Gauges and other precision measuring instruments are often hardened to improve their wearing

properties; unfortunately they are then liable to alter in length over a period of months or years

a process known as secular change. This change can be almost eliminated by stabilizing, which

consists of tempering several times at about 150 OC. The processes described above are

usually termed low-temperature tempering, and are intended to retain most of the hardness of

the quenched steel, but there is another tempering range from 450 OC to 650OC; this range is

used when steel are required to be tough rather than hard. Plain carbon steels from 0.3% to

0.6% carbon are often quenced and then tempered in the upper range. They are harder and

more shock resistant than the same steel in the normalized state, but are still machine able.

Many alloy steels, particularly those containing nickel and chromium with low mass effects, only

shown their best properties after hardening and tempering temperatures, the final properties can

be varied over a wide range of hardness and strength values.

It should be noted that all tempering is done below the lower critical point. Generally, it is not

advisable to hold steel at a temperature within the critical range.

HARDENING AND TEMPERING PRACTICE

In the workshop carbon-steel tools are often hardened and temperature with the aid of a small

gas-fired furnace or the block smiths hearth. They are heated to above 800 OC (the temperature

being judged by the colour) and then partially immersed in water, the cutting point being held

downwards to ensure its being quenched. Part of the tools shark remains red hot, and on

removal from the water the heat from the shank flows back to the cutting point and tempers it.

This method is only possible due to the peculiar oxidisation of the steel. When the cold cutting

point is removed from the water it is quickly polished and watched carefully. At about 220 OC a

faint yellow oxide film forms on the surface of the steel. This colour slowly turns to brown, then

to purple and finally to blue at about 300 OC. In the case of an orthodox cutting tool the effect

produced in that of a band of colours, headed by yellow passing slowly down to the point of the


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tool. When the desired colour reaches the tool point, the whole tool is quenched out. The

following list gives the tempering colour and typical articles tempered.

The method outlined above is not suitable for parts which require hardening throughout their

length. In such cases the part may be quenched out in water, and then held over a heated iron

plate until the tempering colours and typical articles tempered.

The method outlined above is not suitable for part which require hardening throughout their

length. In such cases the part may be quenched out in water, and then held over a heated iron

plate until the tempering colour appears. By skilled manipulation an article of irregular section

can be tempered in this way. The surface temperature only is indicated by the colour, but a

good craftsman, tempering the tools and observing the results in service, can produce good

work by hot plate tempering.

By far the most accurate method of tempering is to immerse the article in liquid at the tempering

temperature. Various liquids are used, such as molten mixtures of tin and lead (solder), various

salts of low fusibility, and even hot oil.

When steel is to be tempered in the high-temperature range, colour tempering cannot be used,

and the part is either immersed in liquid or a furnace is held at the desired temperature.

Temper Colour Actual Temperature Articles

Pale Yellow 230OC Planing tools, brass turning tools

Deep Yellow 240OC Drills, milling cutters

Brown 250OC Taps

Brown-Purple 265OC Punches

Purple 275OC Chisels

Blue 300OC Springs

CASE HARDENING

As distinct from hardening of parts throughout most articles need a tough strong core and a very

hard surface to resist wear such as pins and rollers, this is obtained by case hardening.


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This finished component made from steel containing about 0.15% carbon is placed in a gas tight

box, surrounded by a mixture of charcoal and barium carbonate (carbon rich material). It is then

heater to 900OC in a furnace for a number of hours.

The low carbon steel absorbs further carbon into its surface and after six to eight hours the

surface may have a carbon content of 0.9% to a depth of 1mm and will thus respond to heat

treatment. But because we have taken the component above the upper critical point the grain

structure of the steel will be coarse and need refining. The component is cleaned and heated to

slightly above the upper critical point of the core (about 870 OC and then quenched in oil. The

core will not have hardened but the case will have a hard but COARSEmartenstic structure.

The component is slowly re-heated to 600 OC then quickly brought up to 760 OC just long

enough to heat the case at this temperature so bring it above its upper critical point.

After quenching the component shall have a strong core and a hard FINE grained case.


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2 Basic Scaffold ConstructionINTRODUCTION

Many accidents are caused by the basic principles of scaffold construction not being fully

understood and by ignorance of the correct function of the various component parts of a

scaffold.

This chapter is an attempt to provide some information on basic scaffolding and to serve as a

guide to:

1. The use and function of various scaffold fittings.

2. The erection of simple scaffolds in common use.

A scaffold is defined any temporarily provided structure on or from which persons work in

connection with building operations or works of engineering construction. It is also any

temporarily provided structure which enable persons to obtain access to places of work. It will

include any working platform gangway, run, ladder, or step ladder, also any guard-rail, toe-board, or any other safeguard and fixing.

SCAFFOLD FITTINGS AND THEIR USES

STANDARDS

Vertical tubes to which the ledgers are fixed. Standards should always be upright or very slightly

inclined towards the building. On all scaffolds over 6M in height the standards should be

staggered at the joints in increase their stability.


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LEDGERS

Horizontal tubes connected to the inside of the standards at right angles, to tie the standards

together. They must be attached using 90Oload bearing fittings. The purpose of the ledgers is to

act as supports of the transoms or putlogs leadgers should also be staggered at the joints to

add strength to the scaffold.

TRANSOM

A short tube fixed at right angles to the top of the ledgers to support the working platform and

held in position by putlog fittings.

PUTLOG

A short tube fixed on top of the ledger to span between the ledger and the wall on a putlog

scaffold. It has one end completely flattened (commonly known as a fish-tail) and it is most

important that at least 56 sq.cm. be inserted between the joints in the brickwork.

DOUBLE COUPLER

The most important scaffold fitting and the

only one which should be used for load

bearing purposes. It is specially designed

for carrying loads and is used for

connecting tubes at an angle of 90O and

must always be used to connect the

ledgers and transoms except the working

lift to the standards. The double coupler

has a swiveled bolt attached to it above

the cup and it is essential that this bolt is

always in the uppermost position above

the ledger. Not only does this make it

easier for the scaffolder so that when he


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has fixed one part of the coupler to the standard the cup will support the ledger even before the

bolt has been tightened, but also should the nut become loose and perhaps even drop off, the

cup will still support the ledge.

PUTLOG COUPLER

Must only be used for securing putlog tubes to transoms to the ledgers to prevent si1deways

movement. They have no load-bearing capacity and must never be usd as a load bearing

coupler.

SWIVEL COUPLER

Used to connect bracings to a scaffold at any angle other than 90 O. It will swivel to whatever

angle is desired. Do not confuse this coupler with the double coupler. They look very similar but

in co circumstances should the swivel coupler be used for load bearing for which a double

coupler has been designed.

BASEPLATE

This is used for distributing the load from a Standard or Raker. It is a square piece of steel atleast 150mm square to give a minimum area of 225 cm2 to comply with the British

Specification. Baseplates help to spared the loads that area imposed on a scaffold and will also

prevent the ends of the standards from sinking into the ground or digging into the wooden sole

boards. They should be used at all times even on concrete floors or pavements and where there

are polished floors the extra area of the Baseplate will provide a friction that assists in

preventing the ends of the standards from slipping. There are also adjustable Baseplates for

taking up variation is ground level.

SOLEPLATE

A good quality timber board of adequate length, usually a scaffold board, used to distribute the

load from the baseplates to the ground. It is essential that the soleplate crosses at least two

standards. Soleplates should always be used on asphalt paths and roofs, grass ground,


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(pavement or earth) or on slippery surfaces such as masble. On surface liable to damage,

(marble, polished floors, etc.) it is wise precaution to place a dust sheet underneath the

soleplate.

SLEEVE COUPLER

Used for joining two tubes together. It is essential that equal lengths of each tube are separately

secured. Recommended for all joints.

PHYSICAL TIES

Extended transoms which pass through a hole or window opening and are securely tied to

another tube at right angles which bears hard on the inside wall, using load bearing couplers.

Scaffolds are required to be tied every 3.6m vertically and every 5m horizontally, and 50% of the

total number of ties required must be physical ties.

REVEAL SCREW

This fitting is inserted into the end of a short length of tube, and by turning the not on the

screw, the tube exerts a friction hold on to two opposing surfaces which as the window sills. Ananchorage point is thus provided to which the scaffolding may be secured. (If must be noted

that the regulations only allow Reveal Screw Ties to be used for 50% of the total number of ties

required on the scaffold). The other 50% must be physical ties.

RAKER

An inclined scaffold tube bearing on the ground at one end and secured to the scaffold (with a

loading bearing coupler) at the other. If over 3m in length it must supported from the scaffold.

BRIDLE

A horizontal tube secured to the underside of transoms or putlogs to support intermediate

transoms or putlogs where as window opening occurs.


26/194

PMI, NTPC 24

GUARDRAIL

Tubes fitted horizontally to the inside of the standards at a height of 1m above the working

platform. (Guardrails must be fitted to every scaffold above 2m in height).

TOE BOARDS

Boards laid horizontally on edge of the working platform and secured to the inside of the

standards by the toe board clips. The minimum width for a toe board is 6 inches and the

distance between the guardrail and top of the toe board should not exceed 0.8m (Toe boards

must be fitted on all scaffolds above 2m in height).

It is essential that all scaffolding materials and fittings should comply with the regulations.

Steel fittings must be periodically checked for serviceability, preferably before each time they

are used.

All the mechanical parts must be sound, free from loose deposits and always well lubricated.

The regulations that are in force for steel fittings also apply to aluminum tubes and fittings.

As the tensile stresses are not the same for aluminum as they are for steel, it is strongly

recommended that only like materials should be used together.

i.e. Steel to Steel Aluminum to Aluminum

GENERAL TERMS

BAY

The space between two adjacent standards along the face of a scaffold.


27/194

PMI, NTPC 25

LIFT

The height from the floor or ground to the lowest ledger, or the vertical distance between

adjacent ledgers.

BRACING

Tubes that are secured to standards with swivel couplers at an angle of 45Oto give the scaffold

stability and prevent distortion.

SAFETY IN SCAFFOLD CONSTRUTION

BEFORE EFECTION COMMENCES

Most scaffolding material has been at some time or another and it is necessary therefore to be

satisfied that the parts are suitable before using them.

In the case of tubes make sure they are not badly corroded. Severe corrosion can be detected

by a thinning of the tube wall at the end, the tube should also be straight and cleanly cut at right

angles. All fittings should be clean and lightly oiled. Never used any fitting that is damaged or

appears mis-shapen.

Inspect the scaffold boards for splits and warping, and make sure that they are free from nails.

The steel band on each end should not be torn, or jagged, and should be securely fixed in

place.

Ladders must not be painted although they can be treated with a clear varnish or a wood

preservative. Check that the stiles are not splintered, cracked, or warped and that all the rungs

are sound and correctly wedged.


28/194

PMI, NTPC 26

ERECTION

Scaffolds should only be erected on a firm foundation. If the foundation is soil it should be well

rammed down to ensure that there are no air packets underneath the crust of the earth. Timber

soleplates should be laid flat on the prepared ground, again ensuring that there is no air space

between board and foundation.

The standards should rest on baseplates and any joints in the standards should be immediately

above a ledger, and should be staggered in adjacent standards, so that they do not occur in the

same lift.

Ledgers must be fixed inside the standards, using load bearing couplers, and they must be

horizontal. Any joints in the ledgers should be staggered so that they do not occur in the same

bay. The decking for the working platform will generally be 200mm x 40mm boards, and each

board should be supported every 1.2m. The boards should be butt jointed but if overlapping is

unavoidable then level pieces of wood should be fitted to the lap joint to eliminate any tripping

hazard. Platform boards should extend at loeas 50mm beyond their supports but no more than

four times their thickness i.e. 40mm boards x 4 = 160mm, 50mm boards x 4 = 200mm.

Always stand ladders on a firm and level base and securely tie them to the scaffold, so that

there is no movement at the top or the bottom. Ladders must extend at least 1.06m above the

stepping off point. Unless specifically designed to be free standing, all scaffolds must be

effectively anchored to the building, or plant by physical ties, to ensure the stability of the

scaffold.

CHECK LIST

1. Baseplates beneath each standard, soleplates if necessary, and standards plumb.

2. Accurate spacing of standards, and lifts, ledgers and transoms horizontal.

3. Sufficient ties effectively made. Even 3.5m vertically and 6m horizontally.


29/194

PMI, NTPC 27

4. All joints in standards and ledgers staggered.

5. Adequate bracing.

6. Correct fittings used.

7. Scaffold is not overloaded.

8. Means of access sound and secure.

9. Any incomplete scaffold properly sealed off or warning notices displayed.

SAFE WORKING LOADS

Very often a scaffold is subjected to many forms of loading, and these can occur

simultaneously.

DEAD LOAD

The weight of the materials employed in the scaffold.

WIND LOAD

The speed of the wind may impose an unusual force on a scaffold, especially if tarpaulin etc.

has been draped over the scaffold, as a means of protection from the elements, or when

sandblasting etc.

SUPERIMPOSED LOAD

The load produced on the platform by materials and equipment and the persons using the

scaffold.


30/194

PMI, NTPC 28

LIVE LOAD

The loading conditions arising from the passage of men and materials along the working

platforms.

MOBILE TOWER SCAFFOLDS

A mobile tower is any tower, where all sides are equal,

formed with standard steel scaffold tube and fittings and

mounted on wheels. The single working platform must not

project beyond the base area and must be provided with

hand-rails and toe boards. The structure must support

(in addition to its own weight and weight of boards) a

distributed load of 45 kgf/m2 over the working

platform. The means of access may be fixed either inside or

outside the structure.

1. Should only be used on a firm and level floor.

2. Should only be moved by pushing or pulling at the base.

3. In addition to normal bracing it must also be provided with plan bracing on alternate lifts.

4. For towers used inside a building the height to the working platform must not exceed 3

times the width of the base; outside a building, 3 times the width of the base.

5. The height of the tower is measured from the ground to the top platform.

6. The height of the lifts shall not exceed 2.6m

7. The bottom lift shall be as close to the wheels as possible.

8. The base width of any mobile tower must not be less than 1.2m.


31/194

PMI, NTPC 29

9. working platforms must be at least 1.2m x 1.2m and every board at least 40mm thick.

Guard rails and toe-boards must be fixed in position.

10. The access ladder must extend at least 1.06m above the landing place and be securely

tied at the top and bottom. It must also be clear of the ground so that it will not foul any

obstruction when the scaffold is pushed along.

11. Wheels and castors must be of the swivel type and fixed in position to prevent accidental

displacement. When the tower is being used they must be braked to prevent movement.

12. The safe working load of each type of castor wheel is usually marked on the body of the

castor and must not be exceeded.

QUICK FORM SCAFFOLDING

METHOD OF ERECTION FOR MILLS LIGHT STEEL FRAMES

1. Base plates to be used on each corner of scaffold to distribute the load.

2. After placing the four base plates in position, place the first two frames parallel to eachother in the base plates.

3. It is now essential to fit a plan brace across the two opposite corners to increase the

stability and rigidity of the scaffold.


32/194

PMI, NTPC 30

4. The distance between the first and successive plan braces should not exceed.

5. Where it is not possible to fix a plan brace such as round a pillar or valve, then a Corner

Tie Bracket may be used.

6. Continue erection by placing successive frames at right angles to the preceding ones up

to the required height, ensuring that the cut out section at the top of all the frames faces

to the inside of the scaffold. (This will give the necessary self-locking effect).

7. A further plan brace or corner bracket should be placed immediately before the last two

frames are placed in position.

The distance between first and successive corner tie brackets must not be more then

3m.

8. Having reached the required height for the working platform the board bearers are now

placed into position. On every scaffold that has an area of more than 0.5m 2at least three

board bearers must be used.

9. Place the selected boards as close as possible on the working platform and if the height

of the scaffold is more than 2.0m to the working platform then toe-boards and guard rails

must be fitted, and the boards securely lashed.

MEANS OF ACCESS

The safest and easiest method is the lashing of a ladder vertically up one side of the scaffold.

The ladder must rise at least 1.06m above the platform height. A ladder should not be placed at

an angle against the top of a free standing scaffold because the pressure applied could cause

the scaffold to fall.


33/194

PMI, NTPC 31

ERECTION OF A GIN WHEEL

If the essential that the outrigger of a Gin Wheel is always secured to two standards and never

to a ledger, transom, or guardrail.

The Gin Wheel must never be supported by a short tube fixed to the scaffolding by only one

coupler. Couplers are not designed to resist the twisting forces that are imposed. The outrigger

must be secured across two standards on an independent scaffold or to one standard and into

the wall of the building on a Putlog scaffold. This is to ensure that there is a downward pull at

one end of the outrigger and an upward pull at the opposite end. Check fittings should be used

above and below the fittings securing the outrigger, as an added precaution, should the

securing couplers slip. The distance from the Gin Wheel to the guardrail is not to exceed 0.76m

maximum.

A ring type Gin Wheel is always to be preferred, but if the Gin Wheel is the type with a

supporting hook then the hook must never be hooked into a coupler. It must be tied tightly to the

outrigger by a figure of eight wire lashing with at least five turns of the wire, and so arranged

that the hook hangs 75mm 100mm below the outrigger. The hook should also be moused to

prevent displacement. Any tendency for the hook to slide along the outrigger can be stopped by

tying the tail of the lashing to the nearest standard or by fixing a coupler to the outer end of the

outrigger.


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PMI, NTPC 32

If the Gin Wheel is fitted with a swivel eye instead of a hook, the eye will slide over a 50mm dia.

Scaffold tube and couplers can be used on either side of the eye to prevent displacement. For

loads in excess of 50kg/f the support should be specialy designed.

Inspect the hoisting rope to ensure that it is sound enough for the job and is marked with a

means of identification. The rope should always be pulled from the side of the scaffold. If it is

pulled from the front it could disturb the scaffold and loosen the putlogs and ties. Winches,

whether hand or power operated, should never be used with a Gin Wheel because the wheel is

not capable of standing up to the loads that winches can impose. The rope dimensions should

be 18mm dia and its length 2 times the distance from floor to Gin Wheel.

MAIN CAUSES OF ACCIDENTS

1. Overloading the scaffold.

2. Concentrated loads at mid-span on the working platform.

3. Removal of bracings and ties.

4. Movement of scaffold boards.

5. Removal of guardrails, handrails and toe boards.

6. Insecure means of access (ladder etc.)

7. Untidy and slippery working platform.

8. Scaffolds not inspected thoroughly (every seven days).

9. Excavating in the vicinity of the standards.

10. Damage by cranes or moving vehicles.

POINTS TO REMEMBER

All the tubes must be straight and all the fittings in good sound condition. Do not mix

steel and aluminum tubes in the same scaffold, as they bend to different extents under

load.

Steel fittings, if used on aluminum tubes, must be sheradised.

Plumb standards, level ledgers and transoms, make sure all fittings are tight.


35/194

PMI, NTPC 33

Use physical ties to make the scaffold secure.

Sec that every board is properly supported.

Fix guard rails and toe boards as soon as possible.

Place material close to standards.

Inspect scaffolds thoroughly before use, and by law every seven days. Store all

scaffolding materials in a safe place when they are not being used.

Keep tubes neatly stacked, and in their respective lengths.

Lubricate all fittings.

BASIC POINTS FOR SCAFFOLD INSPECTION

1. Make sure that the scaffold is rigid, firm and stable.

2. Ensure that all tubes are in position.

3. Inspect tubes for damage. (This could be caused by vehicles bumping into the

standards, by crane loads striking against the framework or even by the scaffolding

being exposed to excessive loading).

4. Inspect physical ties for security, and ensure that any reveal ties so used are firmly in

position.

5. Examine all the couplers for security and tightness and ensure that none of the bolts

have commenced to work themselves loose.

6. Ensure that the working platform is free from rubbish or unnecessary obstructions and

that no nails are projecting from the boards.


36/194

PMI, NTPC 34

7. Have any slippery boars cleaned and sanded as soon as possible.

8. Check that the toe boards and guard rails are secure and firmly fixed in position.

9. Ascertain that the ladder access still extends 1.06m above the landing place and is

securely lashed in place.

10. Report any damage to the rungs or stiles of the ladder and warn persons of the danger.

SEVEN RULES FOR THE INSPECTION OF SCAFFOLD BOARDS

1. No knot or knothole may exceed 50mm in diameter and no cluster of knots or knotholes

may exceed 50mm in overall diameter.

2. No knot or knothole on the edge of the board may exceed 40mm across the face or

15mm across the edge.

3. The board must be flat and free from twist.

4. The width and thickness of the board must be constant though out its length.

5. The board must not be split, even part way.

6. The ends of the board must be bound with metal hoops, in a manner that wil not cause

injury.

7. The board must be free from any grain disturbance. (This appears in the form of waves

in the normally straight grain of the flat face of the board and as cross-grain on the edge

of the board. These defects can cause weakness.


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PMI, NTPC 35

SOME DOS AND DONTS

1. Wear a strong pair of shoes, preferably rubber soled. Wellingtons, and training shoes,

are not suitable footwear for erecting scaffolds.

2. always wear a safety helmet when working on scaffolding, and when working at heights

make sure the chin strap is in position (under your chain).

3. Use a proper scaffolding spanners, never use an open jawed spanner.

4. Do not carry materials up or down the access ladder, use a hand line, or rig a gin wheel.

5. If possible rope off, or suitably fence off, the area around the scaffold.

6. Should the erection of the scaffold the left overnight, see that no loose material is left on

the party erected scaffold, remove any ladders, and hang a SCAFFOLD INCOMPLETE

notice in a prominent position.

7. Keep all tubing in good sound condition, make sure all the fittings are in good working

order and well lubricated. A life may depend on it, and that life COULD BE YOUR OWN!


38/194

PMI, NTPC 36

3 Slinging MethodsINTRODUCTION

Accidents which occure when lifting tackle is being employed are mainly caused by unfamiliarity

with the tackle and unfamiliarity with the correct principles.

Ignorance of the low is a contributory factor, and violation of regulations, whether inadvertent or

deliberate, must lead to unsafe practices.

This chapter is an endeavour to provide some information on the construction of lifting

equipment, the legal requirements for such equipment and some guidance as to its proper use.

The chapter is an endeavour to provide some information on the construction of lifting

equipment, the legal requirements for such equipment and some guidance as to its proper use.

The regulation demand that all lifting gear and appliances shall be:

1. Of good construction.

2. Of sound material.

3. Of adequate strength.

4. Free from patent defects.

5. Clearly marked with the Safe Working Load.

6. Tested and thoroughly examined by a competent person before being used for the first

time. (A test certificate specifying the Safe Working Load (S.W.L.) is given by the

examiner).


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PMI, NTPC 37

7. Recorded in a register which must be kept available at all times.

8. Examined by a competent person at least every six months (or other period as

specified).

9. Maintained in an efficient state, in efficient working order and in good repair.

The intention behind these regulations is to ensure that only approved equipment is employed,

that, al all items, it is strong enough to do the work it is intended for, and that the person using it

is aware of its capabilities.

The use of any tackle that does not conform to all the above requirements is not only dangerous

practice, it is illegal. Regulations require that all gear and appliances be examined by a

responsible person prior to issue.

Although the gear is subject to periodic inspections, there can be no guarantee that defects will

not develop in the period between inspections, so, in the interest of safety, THE PERSON

USING THE EQUIPMENT should examine it before use to ensure it is in good condition.

IF THE CONDITION OF ANY PIECE OF EQUIPMENT GIVES THE SLIGHTEST CAUSE FOR

CONCERN, IT SHOULD NOT BE USED UNTIL IT HAS BEEN EXAMINED BY SOME

COMPETENT PERSON.

The safe use of lifting tackle demands recognition of the following points:

1. Only the right kind of gear must be employed.

2. It must be approved gear to standard specification.

3. The operator must know the strength of the tackle.

4. The equipment must be free from any defect that may reduce its S.W.L. to a dangerous

extent.


40/194

PMI, NTPC 38

5. It must not be used in any fashion which induces additional stresses which may overload

it.

Defects will occur even if tackle is used and maintained correctly, but they are aggravated by

improper use and a failure to maintain properly.

SAFE WORKING LOADS

The definition of the safe working load (S.W.L.) is the maximum load the equipment can handle

safely.

All the equipment has a margin of safety between the figure given for its use and actual

maximum capacity.

Eye-bolts, shackles, etc are Proof-loaded by the manufacturer to twice the S.W.L. figure

Chains, ropes, etc. are given a much greater margin of safety because they are more prone to

damage and subject to the possibility of greater unforeseeable stresses.

Samples are tested to Failure Load to determine their absolute capacity and given a very much

reduced figure as the S.W.L.

This margin of safety, which may very depending on the tackle and the circumstances under

which it is employed, is known as the Co-efficient of Utilisaton.

What must be realized however, is that the S.W.L. figure derived from the above, is only valid if

the equipment is in good condition, and is not being employed in any fashion or under any

circumstances that impose abnormal stress. Such abnormal stresses should, of course, be

avoided if possible, but if they are present the operator must give full consideration to such

factors when selecting equipment.

Despite the wide margin of error for safety it is easy to eliminate this safety factor if the tackle

has depreciated, or any aspect of the work enhances the load on the equipment.


41/194

PMI, NTPC 39

Extreme heat, for instance, demands the use of tackle with increased S.W.L. capacities. Usually

cordage used in such conditions is given a load factor of 8, but, even so, it may still be

necessary to use stronger equipment than would normally be employed.

The use of bights, back-hooking (snickling), or bending cordage over any small radii under load,

these procedures create stress on one particular section of the rope and there may be induced

friction. The S.W.L of the tackle is impaired, and stronger gear is necessary.

Shock loading can impart severe stress on ropes and chains. There is always a possibility of

this when a load is snatched, but it may become extreme on occasions such as a valve

suddenly coming loose from its seating. Where such possibilities exist, it pays to err on the safe

side in the selection of tackle.

Angular stress on ropes and chains influences the S.W.L. and as the distance between the sling

legs increase the S.W.L. decreases.

Manufacturers concern about this fact has resulted in multilegged slings assembled on a ring

now being tested and rated at angles of 90Oor 120Oand stamped accordingly.

This equipment an therefore be used to lift the stated S.W.L. up to and including the given angle

but attention is drawn to the fact that the load to be lifted or the included angle should never be

greater than those marked.

Single slings will, in the future, also be marked with the S.W.L. at various angles, but when they

are used in combination to make a multilegged sling the angle must not exceed 90O.

At 120Othe S.W.L. of two single slings is only equal to that of a single sling and any additional

angle could result in extremely dangerous circumstances. At slightly above 150O the slings

would be stressed to failure load.

The angle is determined by the length of the sling legs compared to the distance between them

at their points of contact with the object being lifted.

If the distance between the sling legs at the points of contact with the load if half the length of

one sling leg, the angle is 30O.


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PMI, NTPC 40

If the distance between the legs is equal to the length of one sling leg, the angle is 60O.

If it is one and a third times the length of one sling leg, the angle is 90O.

One and two thirdtimes the length of one sling leg, the angle is 120O.

At angles in excess of 90O only made-up slings of two and four legs may be employed

because this increases the stress on the rope or chain to dangerous limits.

Three-legged slings may only be used a angles up to 90O.

The use of long slings and care in selection of attachment points can eliminate the need for

wide angles.

This stress induced by wide angles means it is

dangerous practice to hummer bights down tight.

A reeved sling with a bight as shown in the diagram

should only be used if unavoidable and the distance from

A-D should never be less than the distance A-B or A-C.

At this point the bight is not very tight but already the angle is 120O. This, plus possible friction at

the bight, would impose excessive stress at this point. Any further tightening would result in a

dangerous circumstance unless due care was given in the selection of the cordage used.

In such a lift is would also be necessary to use packing at points where the load contacts the

rope.

It is common practice to use span wires to support lifting equipment when faced with an

absence of proper lifting points. Often such ropes are stretched as taut as possible and a

dangerous situation may arise.

A span wire is merely an inverted sling and when the lifting tackle is suspended from it we are

again faced with angular stress.


43/194

PMI, NTPC 41

If a span wire were subjected to a load of 1 tonne and the angle at the point of suspension was

160O(a very commonplace occurrence) the stress on the rope at each side of the load would be

3 tonnes. The ropes safety factor of 5 would be eliminated.

If this method of work must be adopted it is essential that full consideration is given to the

strength of the span wire and the points of attachment to ensure they cope with any angular

stresses that may be imposed.

Where there is difficulty in assessing the weight of the load it is sound practice to use tackle with

a S.W.L. in excess of what is estimated as being sufficient.

Wherever possible it is suggested that objects should have the weight stencillied on and also be

included in a register.

This removes doubt and allows the operator to work with less worry, but in the absence of such

considerations, where he must make his own assessment, there must be greater care in the

selection of tackle and any error must always be on the Safe Side.

Some guides as to weights of various materials are given here in the hone they help in this

context.


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PMI, NTPC 42

WEIGHTS OF MATERIALS

Per Metre Run Rolled Average weight per m3

Steel Joists

Size in mm kg Tonnes

(t)

With Taper ( 75 x 51 7 Loose cement 1.45

Flanges ( 152 x 89 17 Reinforced concrete 2.40

( 178 x 102 22 Wet earth or dlay 1.60

( 203 x 102 26 Wet sand 1.93

Gravel 1.77

( 254 x 102 28 Loose coal 0.90

( 305 x 120 33 Brickwork 2.01

( 356 x 127 39 Water 1.00

( 381 x 152 67 Petrol 0.68

( 406 x 178 74 Steel 7.90

( 457 x 152 82 Lead 11.45

( 610 x 229 140 Cast Iron 7.24

Per Metre Run Round Average weight per m2

Steel Bar

Dia in mm kg kg

13 1.00 Plates 6mm thick 47

25 3.9 Plates 9mm thick 71

38 8.9 Plates 12mm thick 9550 15.4

75 34.7

100 61.7

150 138.9


45/194

PMI, NTPC 43

Low Pressure Pipes Steel Section Bar

Bore in mm Kg Size in mm Metres per tonne

Steel 25 3 50 x 50 51

Steel 50 7 64 x 64 31

Steel 75 12 75 x 75 23

Steel 100 15 90 x 90 16

Cast Iron 100 24 100 x 100 13

Cast Iron 150 45 115 x 115 10

Cast Iron 200 66 130 x 130 8

Cast Iron 225 78 150 x 150 6

Cast Iron 300 121

Cast Iron 450 221

Cast Iron 600 331

FIBRE ROPE AND FIBRE ROPE SLINGS

Fibre ropes may be made from various natural products, Sisal, Hemp, Coir, Cotton, Manilla etc.

but is is recommended that among the natural fibres only Grade I Manilla be used for lifting.

The strength of fibre rope is determined by the ropes size (circumference) the material used in

its manufacture, and its condition.

Three values are given to the condition of fibre rope.

1. Excellent

This is rope direct from the manufacturer, or rope that has not been used and has not

been permitted to deteriorate.

The quoted S.W.L. applies only to rope in this category.

2. Good


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PMI, NTPC 44

This is rope which has been used with only a slight loss in fibre strength and has a

maximum of 20% reduction in quality from new. An allowance in the S.w.L. must be

made for any deterioration.

3. Fair

This applies to rope which shows clear sign of wear and tear or interior deterioration.

This must not be used for lifting or supporting loads. It may be used for tying, etc., where

there is no possibility of damage to persons or goods, but it is suggested that rope with

over 20% deterioration should be scrapped to prevent possibility of wrong usage.

Fibre ropes are easily damaged and will deteriorate naturally even when used correctly and

cared for in proper fashion, but improper use and lock of care results in more rapid deterioration.

They are adversely affected by damp or heat and should be stored in temperatures of 10O-

20OC. Wet ropes should not be allowed to remain in damp circumstances, neither should they

be dried out too quickly. They should be permitted to dry out naturally in the temperature given,

and inspected prior to use.

They are easily contaminated by oil, chemicals, acids, or noxious fumes. If there has been any

possibility of such contamination, the rope should not be used until it has been examined by

some competent person.

Ropes must be protected from sharp corners or edges and from any rough surfaces that may

cut or chafe them. The use of packing, such as wood or Hessian, at points of contact between

rope and load, will eliminate much of the wear and tear that often occurs, as will the use of

correctly sized pulleys that permit the rope to fit and run properly.

ALL FIBRE ROPES SHOULD BE INSPECTED BEFORE USE FOR INTERNAL OR EXTERNAL

DAMAGE.

A warning sign of broken fibres is when short tufts stick out at right angles to the rope. Any

variation in the thickness of the rope should also be noted.


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PMI, NTPC 45

To examine the interior, twist the rope between the hands so the inside is exposed. The fibres

should be of good colour. Any discoloration implies probable contamination.

If the rope smells musty, or if any dry dust is present, these are also sure signs of contamination

or ageing. When the rope is released it should spring back into its normal lay if the fibres are in

good condition and have retained their normal flexibility.

IF THERE IS ANY CAUSE FOR CONCERN REGARDING ANY OF THESE FACTORS, OR IF

THERE IS ANY DOUBT ABOUT THE ROPES CONDITION, IT MUST NOT BE USED.

TABLE I

Safe Working Load of Multilegged Slings with Ring Attachment. SWL calculated at 90Orated as

follows:

For 2 leg slings 1.40) x S.W.L. of single leg

For 3 leg slings 1.60)

For 4 leg slings 2.00)

Nominal SAFE WORKING LOAD

Diameter __________________________________________________________________

of Rope Single Part 2 Leg Sling 3 Leg Sling 4 Leg Sling

mm kg kg kg kg

8 68 95 108 136

10 89 124 142 178

12 134 187 214 268

13 158 221 252 316

14 180 252 288 360

16 254 355 406 508

18 305 427 488 610

20 406 568 649 812

22 483 676 772 966

24 571 799 913 1142

26 666 932 1065 1332


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PMI, NTPC 46

This, and the following, table applies to Grade 1 Special Quality Manila Rope, plain load, of 3

strands.

TABLE II

Safe Working Loads of Single being used in pairs at angles of 0O 90O.

Nominal Diameter S.W.L. of S.W.L. of Two Slings

of Rope Single Part ---------------------------------------------------------

OO +OO 90O

-------------------------------------------------------------------------------------------------------------------------------

mm kg kg kg

-------------------------------------------------------------------------------------------------------------------------------

8 68 136 95

10 89 178 124

12 134 268 187

13 158 316 221

14 180 360 252

16 254 508 355

18 305 610 427

20 406 812 568

22 483 966 676

24 571 1142 799

26 666 1332 942

When a single sling is revved with a bight the angle at the bight should never exceed 120O(see

section on S.W.L.s)

At this angle (120 O) a single sling would have a S.W.L. equal to half the figure in the first

column: e.g. 16mm rope S.W.L. 127kg. An endless sling so used would have a S.W.L.

equivalent to a single part, e.g.

16mm rope S.W.L. 254kg.


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PMI, NTPC 47

WIRE ROPE AND WIRE ROPE SLINGS

Because a wire rope is made from steel this does not mean that we can treat it with a lack of

concern. It is subject to wear and tear and will depreciate naturally when in use, but again this

deterioration is accelerated by improper use and lack of care. A knowledge of its structure and

composition will help to understand why this happens.

Usually, wire rope has six strands, each composed of a varying number of wires. The number of

wires per strand, plus their size, quality, and formation, determines in ropes surround a wire

rope core which gives greater strength and longer life but with some reduction in flexibility.

The older ropes have a fibre core which adds greatly to the ropes flexibility.

ANY DEPRECIATION OF THIS CORE MAY PERMIT INTERNAL CORROSION AND

DAMAGE, AND RESULT IN A LOSS OF FLEXIBILITY, AND IF SUCH ROPES ARE STILL IN

USE A NOTICEABLY REDUCED FLEXIBILITY SHOULD BE SUSPECT.

The size of a wire rope is measured in terms of its diameter, and all wire ropes should be

marked with the S.W.L. which again is only valid if the rope is in good condition and is being

employed in a manner which does not subject it to abnormal stress.

Before use, wire rope should be examined for obvious defects such as broken wires, flats on

individual wires, dangerous kinks where flats and breaks readily occur, or any apparent

corrosion. These defects are created mainly by improper use, and observance of the following

points will reduce the possibility of damage.

1. Loads should not be snatched from the floor. The leads to excess tension on the rope

and opens out the strands. The weight of the load should be taken gradually.

2. The rope must be protected from sharp corners, edges, and rough surfaces. Again, the

use of Hessian, or wood, at points of contact between rope and load, can prevent

kinking and cutting and cordage. Rough pulleys, or the use of pulleys that do not permit

the rope to fit correctly, contact with blocks, etc., may cause serve chafing, especially if

such contact is repetitive.


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PMI, NTPC 48

3. Taking a rope over a girder, or similar object, then imposing a load on it, will create kinks

and flats on wires. The use of a girder clamp can prevent such occurrences.

4. Slings should never be dragged from under a load resting on them. The load should be

set down on blocks, leaving the sling free for extraction.

5. Wire rope should not be bent over any diameter that is too small. This is certain to kink

the rope, with the other detrimental effects ensuing, and these kinks can never be

straightened out. A rough guide to pulleys is that diameter of the pulley should be at

least 24 times the diameter of the rope.

EXAMPLE

10mm Rope 240 mm Pulley

6. Wire rope should never be knotted.

7. Rope should never be allowed to remain for long periods on could concrete floors.

8. Ashies, clinker, coke breeze, even smoke of chemical fumes can have detrimental

effects on wire ropes and when any of these conditions is present, care is essential, and

regular inspections necessary.

9. Rope should be inspected regularly for any dirt or grit between the strands and cleaned

with the wire brush.

A certain amount of wear and tear is unavoidable, and, with rope in regular use, broken wires

are inevitable. However, these must always be regarded as a WARNING SIGN, and there is a

limit to the number that can be tolerated without the rope weakening and perhaps becoming

unserviceable.

The Regulations say, No rope shall be used in hoisting or lowering, if, in any 8 diameters of the

rope, the total number of wires in the rope.


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EXAMPLE

A 9mm rope containing 6 strands of 36 wires (6 x 36)

8 diameters = 72mm 6 x 36 216 wires.

If in any 72mm of rope there wire more than 21 broken wires, the rope should not be used.

The Regulations says No wire rope shall be used if in any length of 10 diameters of the rope,

the total number of visible broken wires exceed 5% of the total wires in the rope.

EXAMPLE

A 9mm rope containing 6 x 36 wires. 10 diameters 90mm. 6 x 36 = 216 wires. If in any 90mm

of rope there were more than 10 broken wires the rope should not be used.

Even when the number of broken wires is less than stated above, it is good practice to return

the rope for inspection by the responsible person and there is still a handling hazard to be

considered.

In the selection of wire rope slings for lifting purposes all imposed additional stresses previously

referred to (brights, angles, etc.) must be considered, as must also the lengths of slings and the

points of attachment which govern the angle of lift. It must also be remembered at this point that

not only must the slings be capable of sustaining the load, but so must all the tackle employed,

lifting points, attachments, and any part of the which is under load.

The figures in the following tables apply to wire rope 6 x 36 I.W.R.C. ordinary lay R.H.

preformed. Minimum breaking load at 180 kgf/mm2.


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PMI, NTPC 50

TABLE I

Safe working Load of Multilegged Slings with Ring Attachment.

S.W.L. calculated at 90O, rated as follows:

For 2 leg slings 1.4 ) x S.W.L. of Single Leg

For 3 leg slings 1.6 )

For 4 leg slings 2.0 )

Nominal Diameter SAFE WORKING LOAD

of Rope mm ---------------------------------------------------------------------------------------------------------

Single Part 2 Leg Sling 3 Leg Sling 4 Leg Sling

9 900 kg 1.2t 1.4t 1.8t

13 1.9t 2.6y 3.0t 3.8t

16 2.9t 4.0t 4.6t 5.8t

19 4.1t 5.7t 6.5t 8.2t

22 5.5t 7.7t 8.8t 11.0t

26 7.7t 10.7t 12.3t 15.4t

28 8.9t 12.4t 14.2t 17.8t

32 11.7t 16.3t 18.7t 23.4t

35 14.0t 19.6t 22.4t 28.0t

38 16.5t 23.1t 26.4t 33.0t

NOTE : S.W.L.s marked on lifting tackles are in kg up to 1000kg and then in tones, to one

decimal place only, except where the figure is 1.25, which in given to two decimal places. E.g.

160kg : 1.25t : 6.9t : 26.4t.


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PMI, NTPC 51

TABLE II

Safe Working Loads of Single being used in pairs at angles of 0O 90O.

Nominal Diameter S.W.L. of S.W.L. of Two Slings

of Rope Single Part -----------------------------------------------------------------

mm 0O +0O 90O

-------------------------------------------------------------------------------------------------------------------------------

9 900 kg 1.8t 1.2t

13 1.9t 3.8t 2.6t

16 2.9t 5.8t 4.0t

19 4.1t 8.2t 5.7t

22 5.5t 11.1t 7.7t

26 7.7t 15.5t 10.7t

28 8.9t 17.9t 12.4t

32 11.7t 23.4t 16.3t

35 14.0t 28.0t 19.6t

38 16.5t 33.0t 23.1t

EYE BOLTS

Eye bolts are mainly used to lift heavy loads that have definite pre-determined lifting points.

The eye bolts should be used for the job it was designed to do and no other purpose, and

only eye bolts of a suitable manufacture should be employed.

HOME MADE EYE BOLTS SHOULD NEVER BE USED NOR SHOULD AN OFFICIAL EYE

BOLT BE MODIFIED TO SUIT SOME PARTICULAR PURPOSE. EITHER PRACTICE IS

DANGEROUS, AND IS AGAINST THE LAW. DAMAGED EYE BOLTS SHOULD BE

SCRAPPED AND NEVER REPAIRED.

The following instructions must be followed.

1. There must be a forged collar and not a welded one at the end of the shank.


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2. The underside of the collar must be machine accurately smooth and at right angles to

the shank. It must also be provided with a recess.

3. The portion of the shank adjacent to the collar must have a specified radius.

4. The screw threads must be clearly cut and of a Standard Specification.

5. Each eye bolt must be proof-loaded to twice its vertical S.W.L.

The reasons for such regulations are easy to realize. It would be dangerous to have welded

equipment unless this was subjected to proper tests. To use any welded tackle without

authorization is dangerous and illegal, because one does not know the strength of the weld. The

eye bolt must be seated properly. It is laid down that when the eye bol is in place, it should not

be possible to get a 0.4mm feeler gauge between the eye bolt and the job. The strength of the

eye bolt is fully dependant on the full purchase of all the threads.

To modify the eye bolt by cutting off part of the shank, or to use packing, such as washers, etc.,

between the eye bolt and the job, means that the purchase of all the threads is not being

employed, so the S.W.L. is drastically reduced. The use of packing also implies that any lateral

pull on the eye bolt could cause the shank to bend. Over tightening the eye bolt, especially by

hammering, or levering, should also be avoided. This may set up shock stresses which could

result in fractures. These may occur internally or they may occur in the shank whilst the eye bolt

is being hammered down; in both cases they will be undetectable.

Before use, eye bolts should be inspected for wear and tear of the threads, fractures, or bruising

of the collar as a result of improper use. After use, they should be stored safely, and not

permitted to be subjected to conditions where the treads may be damaged or become clogged

with dirt.

The S.W.L. on an eye bolt is only true when the pull on the eye bolt is vertical. Any lateral stress

imposed by inclined sling legs seriously effects the safe aspects of using eye-bolts, so any

angular stress should be avoided. Where an angled lift is unavoidable, then eye bolts with

integral links should be used.


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PMI, NTPC 53

Safe Working Loads of Eyebolts under Vertical or Inclined Conditions of Loading

Metric Thread Safe Working load Maximum load to be lifted by to`

For single eye-bolt eyebolts when the slings are at

VERTICAL an angle

mm 0O 30O 30O 60O 60O 90O

12 300kg 400kg 250kg 150kg

16 600kg 800kg 500kg 300kg

18 1.0t 1.3t 800kg 500kg

20 1.25t 1.6t 1.0t 600kg

22 1.6t 2.0t 1.25t 800kg

24 2.0t 2.5t 1.6t 1.0t

27 2.5t 3.2t 2.0t 1.25t

30 3.2t 4.0t 2.5t 1.6t

33 4.0t 5.0t 3.2t 2.0t

36 5.0t 6.3t 4.0t 2.5t

39 6.3t 8.0t 5.0t 3.2t

45 8.0t 10.0t 6.3t 4.0t

mm 0O 30O 30O 60O 60O 90O

52 10.0t 12.5t 8.0t 5.0t56 12.5t 16.0t 10.0t 6.3t

64 16.0t 20.0t 12.5t 8.0t

70 20.0t 25.0t 16.0t 10.0t

76 25.0t 32.0t 20.0t 12.5t

In the case of inclined loading the S.W.L.s are only applicable when the tension is applied in the

plane of the eye.

Despite the above warning on the use of washes, in the event of eye bolts being used in pairs

and being slightly out of line when screwed down to the correct degree, a special washer can be

employed to remedy this adverse circumstance.


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PMI, NTPC 54

On no account should eye bolts be used a turn a load over on to its side from vertical, or vice

versa.

SHACKLES

The most important part of the shackle is the pin, because this is subjected to the greater part of

the stress from the load. It is vital that it is the correct type for the shackle and complies to the

regulations which say.

1. The pin must be forged or machined from mild steel or high tensile steel or appropriate

standard specification.

2. The diameter of the pin must not be less than the diameter of the Bow or Dee.

THE USE OF ORDINARY NUTS AND BOLTS, OR ANY OTHER MODIFICATION, IS

EXTREMELY DANGEROUS PRACTICE AND CONTRARY TO LEGAL REQUIREMENTS.

Very often shackles (or other equipment) can be used advantageously to do jobs of a special

nature, but this does not imply that deviations from standard procedure can be adopted or

unlawful modifications to the tackle permitted. In such cases it may be possible to obtain a

specially constructed piece of tackle which can be tested and approved. This will result in safer

work and comply with legal requirements.

More concern in this respect can eliminate many dangerous practices, and it is suggested that

the provision of special equipment, where this is required, is the only way to prevent the need

for dangerous modifications to existing equipment, or the use of such equipment in improper

fashion.

USE OF EYE BOLTS WITH SHACKLES

The eye of a bolt of the correct design is always too small to admit safely the hook of a crane or

block that has the same S.W.L. This means the SHCKLES MUST BE USED TO CONNECT

THE HOOK TO THE EYE BOLT.


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PMI, NTPC 55

Some eye bolts that do permit the use of a hook direct are still in use, but their employment is

undesirable.

When using eye-bolt in pairs, it is common practice to take

a sling from the crane hook, through one shackle and

across to the other shackle, then back to the crane hook.

This is wrong, because it sets up two tensions, the

normal vertical tension to the crane hook, and a horizontal

tension between the eye bolts. This produces stress far is excess of what can normally be

anticipated and also induces exceptional wear and tear of the cordage where this is revved

through the shackles.

At some future date a new design of eye bolt will be available which will permit direct application

of the hook.

BULL-DOG GRIPS

When properly applied, these afford a simple and effective means of securing the ends of a

rope as an alternative to splicing or socketing.

The use of them for lifting should not be encouraged and in this capacity they should be

regarded as a TEMPORARY MEASURE ONLY. Great care in their use for such work in

imperative.

The use of bull-dog grips haphazardly as is accepted practice is extremely dangerous. The

following hints may assist in safer use of this type of equipment.

The U-bolts must never be placed in contact with the working part of the rope. This lowers the


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PMI, NTPC 56

efficiency by 25% or more.

When being use in this fashion, securing to a thimble or forming a loop, bull-dog grips should be

spaced at approx. 6 rope diameters apart.

The minimum number of grips for any connections is as follows:

Rope up to 19m not less than 3 Grips

Over 19mm up to 32mm not less than 4 Grips



Over 44mm not less than 7 Grips

EXAMPLE: For 26mm rope not less than 4 Grips would be employed, spaced approx. 150mm

apart.

If a rope fitted with bull-dog grips is being used for any purpose that puts it under stress an

inspection should be made following an initial strain on the attachment. It will usually be found

that some adjustment to the nuts is needed.

Serving the rope where the grip has to seat, or wrapping with material such as canvas will

improve the efficiency of the connection.

IF ALL CORRECT MEASURES ARE TAKEN, THE CONNECTION SHOULD HOLD APPROX.

85% OF THE ACTUAL BREAKING LOAD OF THE ROPE USED.

To join two ropes using bull-dog grips the above conditions still apply, but double the number

of grips must be used.

To joint two 26mm ropes it would be

necessary to use 8 grips, and they must

be fitted in the fashion shown below.


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basic maintenance aspect

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