safety in engineering paper iii

7/27/2019 Safety in Engineering Paper III

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SAFE GUARDING THE POINT OF OPERATION

DEVICE BARRIER

GUARDS

(CONTROL ACCESS TO THE POINT OF OPERATION) (BAR ACCESS TO THE POINT OF OPERATION)

EMPLOYEE CONTROLLING MACHINE CONTROLLING EMPLOYEE CONTROLLING AND

MACHINE CONTROLLING

PULL BACK OR PRESENCE SENSING TWO HAND CONTROL

PULL OUT

RESTRAINT

FIXED BARRIER GUARDS ENCLOSURE GUARDS ADJESTIBLE BARRIER GUARDS INTERLOCK

BARRIER

GUARDS

(Guards are made up of woven wire, expanded metal, perforated metal, sheet metal, wood or metal strips (crossed),

wood or metal strips (not crossed), plywood/plastic, standard railing.

Types of Guards :

1. Fixed GuardBest guard. fixed guard should be used as Feras Possible. This should be used when access to the

dangerous parts of the machine is not required frequently.

2. Interlocking GuardWhen it is not prachable to use fix guard on a dangerous part of M/c, Interlocking guard

can be used the interlocking device may be mechanical or electrical. The guard will safe guard the dangerous parts of

the M/c from the start to the m/c come to rest.

3. Trip GuardWhen both the guards are not possible, trip guards are used whenever, hand of operater reaches

towards moving / dangerous part of M/s beyound a certain limit, the trip guard get actuared and stop the m/c. The trip

guard may be creatical, infra red or photo electric.

4. Automatic GuardIt will automatically remove the hand of operater out of dangerous area.

5. Two hand Control guardWhen more than ohe parsen are working an a M/c trip guards are to be used. The M/c can not start the both hands of operater are not engaged sima housing.

Dangerous Parts of M/c which must be Guarded

1. Paint of operation.

2. Transmission Machinery

3. Any other dangerous parts.


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hands of the operator are kept engaged away from the danger area. If more than one person is to work on a machine,

two hand control device should be provided for each operator and unless all the operator operate their device together

the machine should not start.

DESIGN ASPECTS OF GUARDS (ERGONOMICS)

Many a time accident had taken place on machihes although the guard was there. This meant that the guards where

not effective and were not functioning for the purpose for which they were installed. There may be some fault in the

design or operation. The following points should be considered in the design of the guard.

It should provide positive protection and prevent all the access to the danger zone during operation. It is not

enough for the guard to give only a signal or an alarm to warm.

It should not cause discomfort or inconvenience to the operator. For example, where a job is to be seen when

it is being worked, transparent screen should be provide instead of blank barrier.

It should not unnecessarity interfere with production.

It should work with minimum efforts.

It should be suitable for the job and the machine.

It should be weaken the structure of the machine. This may arise when guards are not incorporated in the

original design and are provided later on.

It should be durable and resist normal wear and shock and should require minimum maintenance.

It should not constitute a hazard by itself. Splinters, sharp corners, rough edges, traps between the guard and

the moving part which it is guarding should be avoided.

As the main function of the guard is to prevent a person coming in contact with moving parts of the machine, data

based on human measurements is very important for proper design of the guards. A person can reach up-

wards, over, into, around and through.

Upward ReachIt the dangerous part of m/c is above 8'6". It is safe. A dangerous part which is beyond an upwardreach of 8'6" is regarded as positionally safe in the absence of conditions to the contrary.

Reach over Barriers

a) If the barrier is low, body can be bent and reach will be longer than the length of the arm.

b) If the barrier is at armpit, reach is equal to length of the arm.

c) If the barrier is above shoulder height, reach is equal to length of the forearm.

d) If the barrier is still higher, reach is equal to the length of the hand or fingers.

Reach into pits

The height of the side of the hoppers etc. determines the extent or reach.

Reach around Barriers

Reach is interrupted by the elbow joint or by the wrist depending upon the length of the side of the barrier and

position of the man in relation to the barrier.

Reach into openings admitting fingers or hand

a) No reach is possible through openings less than 1 cm 1 cm.

b) If opening admits one, two or three fingers, reach is restricted to maximum length of the largest finger.

c) If opening admits four fingers, than size and shape of the opening will be an important factor in determining

the extent of reach.

d) If opening admits four fingers and the thumb, reach is limited by -

i) thickness of the bond

ii) thickness of the wrist


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Fencing of Machinery (Guards)

Every moving part of prime mover.

Every flywheel connected to prime mover

Headrace & tailrace of every water wheel & water turbine.

Any part of stock-bar which project beyond the head stock of lathe

Every part of an electric generator, a motor, or rotary convertor.

Every part of transmission machinery

Every dangerous part of any other machinery

Shall be securely fenced by safeguards of substantial construction

Wood Working Machinery(Wood Wokring Machinery means of circular saw, and saw, planning machine, chair

mortising machine or vertical spindle moulding machine operating on wood or cork. Circular saw means working in

a bench which is moved towards the wood for cutting operation. Band Saw means a band saw, the cutting portion of

which runs in vertical direction. Planning Machine means a machine for overhead planning or for thickning or for

both operations.)An efficient stopping and starting device shall be provided on every wood-working machine.

Every circular saw shall be fenced as follows:

Behind and in direct line with the saw there shall be an arriving knife, which shall have smooth surface, shall be

strong, rigid ans easily adjustable. The distance between the front edge of the knife and the teeth of the saw shall not

exceed 10 mms. For a saw having dia. of


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operator from the danger zone at every descent of the blade, punch or stripper cutter. All couplings with projecting

bolt heads and similar projections shall be completely encased or effectively guarded as to prevent danger.

Guarding of different machines

Machines Dangerous Parts Types of Guard

Textile machinery

Blow room machines Main drive, beater cover, grid bars, dust Separate motors, belt shifting device,chamber interlock guard, fixed fencing.

Lap M/c Lap forming rollers. interlock guard

Carding M/c Cylinder interlock guard

Speed frames Headstock interlock guard

Calendering Running rolls Nip guard

Cotton Ginning

Line Shaft to run the gins Line shaft Wall or fencing with locking doors.

Wood Working Machinery

Circular Saws The Saw A riving knife of prescribed dimestions

and setting.Adjustable top guards, two metal

plates guard, push sticks.

Band Saw Top & bottom pulleys and the blade Fixed guards

Planning machine Cutting slot, freed roller Bridge guard (adjustable) - bridge

guard above the cutter to reduce

access to the cutter. Should be wider

than the gap in that table, to prevent

contact of hand with cutter

Rubber Mills

Rubber mill In-running rolls Height>96.5cm, a distance guard.Trip guard within 1.8m height

Calender machine In-running rolls Trip guard within 1.8m height, tight

wire cable connected with it.

Other machines

Pedestral Grinder Grinder wheel Adjustable safety glass screen

(Bench grinder)

Power Press (Punching) Point of operation - punch point Fixed mesh guard in front of punch

continuous point.

Power Press (Punching) Punch point Interlock guard.

Single strokeHand operated press Punch point Sliding guard - if ram goes up guard

also slides out side.

Milling machine Point of operation Telescopic guard, two piece barrier

guard-guard is just front gate.

Drilling machine Point of operation Telescopic guard for radial & heavy

pedestal drilling m/c.

Sensitive trip bar - Sensitive trip bar

suspended closed to the drill

swithces off power supply and

applies a brake if the trip bar is

deflected. The Sensitive trip bar is

telescopic so that it can be adjusted

to suit the length of the drill.


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HAND TOOLS AND POWER TOOLS

Main Causes of Tools Accident Each year hand tools are round to be the source of about a percent of all

accidents reported under the factories Act. In all branches of industry numerous hand tool and powered tool injuries

are observed. Disabilities and injuries resulting from hand and powered tools include loss of eyes and vision, punc-

ture wounds from flying chips, severed fingers, arteries etc. broken bones, contusion, infection from wound and

numerous other type injuries. The proportion of permanent disability case from the use of hand tools is low ascompared to such in many other activities like machine operation etc. flying particles from mushroomed heads, over

tempered points may cause many serious accidents. Many fatalities result from the use of electric powered hand

tools. The minor injuries in hand tool accident are too large i.e. the lost time due to injury is high enough and

alarming. Therefore hand tool injuries should be prevented and it is always profitable. Different types of hand tools

are used in different industry, mainly in metal working industries and wood working trades. But some tools are

common to all industries and woodworking traders. But some tools are common to all industries. Hand tools are also

used in maintenance and repair work, construction, logging and lumbering. Certain special tools are also used for

special purpose. It is mainly the responsibility of the supervisory staff to keep the tools in safe working condition, to

check the unsafe methods of use of tools, to select the right tool for the right job and making the working mass awareof reduciing the injuries.

The main causes of the tool accident (hand tool or powered tool) may be summarized as :

1. Wrong selection of tools.

2. Improper use Due to lack of Knowledge and lack of supervision.

3. Unsafe condition (Using Defective tools)

4. Improper Storage / Stacking

5. Improper Carrying.

6. No ear thing of electric tools

Control :

1. Proper Supervision

2. Proper selection of tool (Proper tool and its material tool)

3. Proper use (at right place in right way)

4. Safe working condition (Proper maintenance and repairing and supply)

5. Selection of right person (Trained person/Skilled person) For Proper job)

6. Proper storage, carrying and repair.

7. Centralized control

Safety practice :1. Always use the proper personal protective equipmentGoggles for eyes, gloves for hands, safety helmet for

head and safety shoes for your legs.

2. Select the right tool for the bojCheck unsafe practices-striking handed surface with hardened head tool using

a wrench as hammer, a file to be used as a pry etc. knife used as a screw driver, pipe used on wrenches leverage etc.

3. Keep tools in good conditionUse of cracked or worm jaws of wrench, screw driver without proper head,

mushroomed head hammer or chisel, hammer with broken handle, dull saws etc.

4. Use tools correctlyThe common causes are : Screwdriver applied to job held in the hand. Knives pulled

towards your body. Hammer striking hardened tool. Placing the fingers or thumb close to the bade when starting its

cut. Pliers and wire cutters cutting a line or repairing files used without handles. Hitting a file with a hammer.5. Keep tools in a safe placeMain cause are: Falling from overhead. Unprotected sharpened adages of knives,

chisels etc. keeping the sharp adags in pocket or tools box exposed.


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available in the stock. The inspection should cover the housekeeping in the tool supply room, tool maintenance,

service number to tools in the inventory handling routinge and condition of the tools. Hand tool receiving the heaviest

wear such as chisels, punches, wrenches, hammers, star drills and black smith's tools require frequent maintenance or

regular basis. Proper maintenance and repair of tools require adequate facilities like-work benches vises, safety

goggles, repair and sharpening tools and good lighting. Specially trained and sklilled persons be engaged for such

work.Tempering of toolsHammber struck and striking tools (Chisels, stamps, punches, cutters, hammers, sledges and

rock drills) should be made of carefully selected steel and heat-treated so tht they are hard enough to withstand blos

without mushrooming excssively and yet not be so hard that they chip. For safety it is better that shock tools some of

which can be dressed frequently, be a little soft rather than too hard, because a chip may fly from an excessively hard

tool without warming when the tools is struck with a harmer or sledge. Tempering of tools is metallurgical process

and require vary special skill. It is a process of heat-treatment or tempering is quite different than the low-carbon mild

steel tools. Therefore before tempering the exact analysis of the tool and its method of heat-treatment should be

ascertained.

Safe-endling of toolsHammer-struck tools, such as chisels, rock drills, flatters, wedges, punches, cold cutters andnumber dies, should have heads property hardened by qualified person. The hazards of burned heads can be reduced

by safe-ending of tools. This can be quickly and economically achieved by grinding or flame-cutting a should recess

about 1/8 inch wide by inch deep into the tool head and then bronze welding it. The proper bore-metal for bronze

welding is 1600 f to 1700 f. the correct temperature is in directed temperature by a bright red colour when the tool is

looked t through dark-glasses in the light of any acetylene flame. Short section of tight fitting rubber hose can also be

set with the striking ends of hammer-struck tools to keep chips off from flying and protect the hand too.

Dressing of toolsShock, cutting and pointed tool require regular maintenance of their edges or striking faces.

Once the cutting or striking faces have been properly hardened and tempered, only an emery wheel, grind stone, file

or oil stone need be used to keep the head in shape and the edges clean and sharp. Proper precaution should be takenbefore grinding hardened tools. They should not be ground untill after they have been drawn or tempered. The

grinding should be done in the specialized way with the proper recommendation of grinding wheel. Each cutting

edge should have correct angle, according to its use and be finished off with a file.

Re-Dressing requires the following

1. Rigidly support the tool being dressed.

2. Use a hand file or shetstone, never a grinding wheel.

3. Restore the original contour of the cutting edge by filling.

Cold ChiselCold chisels are hardened on the cutting edge. Dressing may be done with a hand file or whetstone

restoring to original shape or to an include angle of 70.

Other commonly used metal working chisels are Roound Nose, Diamond Point and cope. Dressing instruction are

same as for flat cold chisels except the bevel angles are as shown.

Hot chisel-same as cold chisels.

PunchesThe working end of pin and rivet punches and blackmith's punches should be observed flat and square

with the axis of the tool. The point of center punches should be redressed to an include angle of 60 while prick

punches to an angle of 30.

HandlesThe tool handles should be of the best straight-grained material. Fitting of handles is very important.

Poorly fitted handles make it difficult for the workers to control the tool. Wooden handles of hand tools used for

striking such as hammer, and sledges. Should be of preferably hickory ash or maple neatly finished. Alternate

materials like fibergladss or steel with a rubber sleeve may be used. Loose wooden handle in sledges, axes, hammers


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iv) Round nose chisel is used for cutting rounded or semi-circular groves.

Chisel should be discarded if it is bent, cracked or chipped. The cutting edge should be redressed to the original

contour when grinding a chisel, the cutting edge should not be pressed hard against the wheel because otherwise it

will be tempered due to the heat generated due to the heat generated due to grinding action. To avoid it, the chisel

should be immersed in cold water frequently while grinding.

Hack SawsHacksaws should be tightened to the frame to avoid breaking and bucking. It should not be tightened

too much to break off the pins to support the balde. Blade should have a forward teeth. 14-teeth blade should be used

for soft metal cutting. 18-teeth blade should be used for cutting steel, iron pipe, hard metal and general purpose. 24-

teeth for drill rods, sheet metal, copper, brass, tubi ng. 32-teeth for thin sheet metal, tubing.

For thin metals at least 2 teeth must be in contact. Force should be applied in the forward stroke with a speed 40/60

strokes/minute.

FilesSelection of right kind of file for the right job should be done to prevent injury and long life. A file should not

be used without a handle otherwise it will damage and puncture the palm. The file should not be cleaned by strking

against vice or any hard surface but a file-cleaning card should be used. File should never be hammered otherwise

hard material will chip and fly to cause injury. For working, the job should be held firmly on vice or clamp and the

stroke of the file be made gently in the forward direction only.

Wood cutting toolsWood chisels, saws, Axes and hatchets.

Wood chiselWood working chisel with wood handle but designed to be struck by wood or plastic, metal, the

handle should be protected by a metal or leather band. Heavy dury chisels made of solid metal handle may be struck

by metal or steel hammer. The finish cuts to be done by hand strokes only. The job must be held firmly in a wire or

clamped properly. The chisel should never be used as pry or wedge. Other use the tool should be kept in rack or tool

bench.

SawsSelection of the proper type for proper job is a vital factor. For fast cross cutwork on green-wood a coaxes

saw (4 to 5 points per inch) should be used. For smooth dry wood cutting a (8 to 10 points per inch) fine saw should

be used. No of points per inch is stamped on the blade. Never drop a saw otherwise the balde may break or get loose.

Use of safety goggles is a must.

Material Handling ToolsCrowbars : Crow bard of proper size with kind of bar for the job should be used. The

crow bar of proper size with kind of bar for the job should be used. The crow bar should have a proper point or toe

of such shape that it will grip the object to be moved and a heel to act as a pivot. The handle may be made as long as

feastible but not too long.

HooksHand hooks for handling of material should be kept sharp so that they will not slip when applied to box or

other object. The handle should be of proper size and shape to suit the hands. The hook tip and handle should lie in

the same plane to give true action to the hook.

ShovelsShovels edges should be kept trimmed and handles should be checked for sprinters. The wearing of safety

shoes be checked for sprinters. The wearing of safety shoes is a must. The workers should carry the load his legs

before striking with a shovel. Dipping of the edge in water time to time keeps the stickly material away off the edge.

When not in use, they are to be kep in racks lying horizontally.

Torsion ToolsTypes : Open - end wrenches, combination wrenchwes, box and socket wrenches adjustable

wrenches, pip wrenc hes, wrenc hes, tongs, pliers etc. the worker should be alert and skillful while using such tools.

The possibility of slipping of the wrench or the job being free or loosing the balance or his body while in action are

variojs causes of the injury. The use must take care of all possible factors regarding the safe condition of the tool and

his own safe way of using the same. The correct size wrench should be selected for a job and never a wrench of

different size be used for the job by grinding its grip to make the size.


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4. Hydraulic.

5. Powder Actuated (Explosive)

The tools like saws, drills and grinders are common to the first three groups. Hydraulic tools are used mainly for

compression work. Powder-actuated tools are used exclusively for penetration work. Cutting and compression.

HazardsA portable power-tool presents similar hazards as a stationery machine of same kind, in addition to the

risk of handling. Burns, cutrs and strains are the main injuries.

Sourcethe sources of injury are Electrical shock

Particles in the eye

Fire

Falls

Explosion of vapours or gases

Falling of tools.

Safety Tips :

1. sources of power should be disconnected before any accessories are changed.2. Before any use / work the guard should be placed in proper position.

3. The tool should not be left in overhed position. It will cause an injury if the cord or house is pulled.

4. The cord or hose should not be kept lying on the floor they will create a tripping hazard. They should be kept

suspended over aisles or work areas.

5. Where it is not possible to keep the cord or hose sususpended they should be covered with wooden planks so that

they are protected from the human contact.

6. While in suspension cord or hose should not disturb the operator's way.

7. The cord should never be hanged sharp edge and should be kept away from oil, hot surfaces and chemicals.

8. Pwer-driven tools while in use should be covered properly otherwise they create hazards if come in contact with

the human body easily.

9. They should be stored properly and never be left encored on the ground.

Selection of toolsSelection of a power tool replacing the hand tool for the same job will increase the degree of

hazard. The hazard will be electrical or mechanical in place of manual. Therefore, the safe design (safe condition)

and proper training (safe use) should be ensured before any power-tools brought into use. Complete information

about the job should be made available so that the tool selected should be most appropriate. The tool selected for

intermittent use or light work are called "home owners grade" and those for hevy decay are called "industrial duty".

Provision of tool-proof training for the proper selection of tools is of.

Inspection and RepairPeriodic inspection is essential for the maintenance of power tools. A schedule be maintained.

Defective tool should be repaired of replaced. Electrical tools should be thoroughly checked visually and also "knock

down" inspection should be carried out at specified intervals. A coloured tag can be attached to the tool last inspected.

The inspection should be done by a skilled and expert person who knows all the checking procedures. Proper

training arrangement should be done for know-how in detail. The responsbility to carry our inspection and the follow

up action should be maintained by a authorized person. Make-shift arrangement must be avoided. No repairing

should be done without proper authorization. Cleaning of the power tools should be done with a recommended non-

flammable and non-solvent. Air-drying should be used in place of blowing with compressed air.

Inspection Checklist :

GeneralLow voltage or battery powered equipment used in tanks and wet areas>

Tools well maintained?


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MANUAL MATERIAL HANDLING

METHODS OF LIFTING

This injuries resulting from manual handling of objective and materials are especially prominent in the total of

compensable injuries. This is obviously a problem for considerable concern to the safety professional, and represents

an area where the biomechanical data relating to lifting and carrying can be applied in the design of jobs and work

layour, which require handling of material. The relevant data concerning lifting can be classficfied into task variables

and human variables.

Task Variables

1. Location of object to be lifted.

2. size of object to be fitted.

3. Height from which and to which the object is lifted.

4. Frequency of lift.

5. Weight of object.

6. Working position.Human Variables

1. Sex of worker

2. Age of worker.

3. Training of worker.

4. Physical fitness of conditioning of worker.

5. Body dimensions, such as height of worker.

Environmental Variables

1. Extremes of temperature

2. Humidity

3. Air contaminants.

Lifiting is so much a part of many everyday jobs that most of us do not think about it. But it is often done wrong, with

unfortunate results; pulled muscles, disk lesions, or painful hernia. Here are siz steps of safe lifting.

1. Keep feet partedOne alongside, one behind the object. Feet confortably spread give greater stability; the

rear foot is in position for the upward thrust of the lift.

2. Keep back, straight, nearly vertical. A straight back keeps the spine, back muscles, and organs of the body in

correct alignment. It minimizes the compression of the guts that can cause hernia.

3. Tuck the chin in so the neck and head continue the straight back line and keep the spine straight and firm.

4. Grip the object with the whole hand. The fingers and the hand are extended around the object you're going to

lift. Use the full palm; fingers alone have very little power.

5. Tuck elbows and arms into the side of body after drawing the close. When the arms are held away from the

body, they lose much of their strength and power. Keeping the arms tucked in also helps body weight centered.

6. Keep body weight directly over feet. This provides a more powerful line of thrust and ensures better balance.

Start the lift with a thrust opf the rear foot.

ACCESSORIES (TOOLS) FOR MANUAL HANDLING covered under hand tools.

WEIGHTS - STATUTORY PROVISION

Adult Male 55kg

Adult Female 30kg

Adolescent Male 30kg

Adolescent Female 20kg


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The following figure indicates the hand signals for use in crane operations. Drivers must only take signals from the

person responsible for the lift and must make no movement until such a signal is given. Only signals in accordance

with the relevant code should be used.

overloading

Overloads are forbidden except of the purpose of a test and the driver should demand a weight check on any

suspected load. The slinger is responsible for ensuring that the load is properly slung before given instruction to the

driver.

Drivers must not lifts any load unless satisfied that it is properly sling and should insist on the safe slinging.

Riding on the load

Under no circumstances must any person be allowed to ride on the load or on the empty hook.

Inspection Procedures

The following are the points to be checked in case of new cranes :

1. Deflection of bridge girders (at full load and at over load)

2. Hoist limit switches3. Trolley travek limit switches.

4. Long travel limit switches

5. Crane bumpers (Spring loaded buffers)

6. Ranaway rail stoppers

7. Insulting rubber mating in operator's cabin.

8. Condition of wire rope (broken wires, abd lubrication, kinks, bends etc.)

9. Anchorage points of wire rope on the drum.

10. Horn or bell.

11. Brke liners and brake drums.

12. Condition of hook, hook block, rope guide, sheaves etc.

The following points should be checked during the regular use of the crane :

1. Condtion of the hoisting wire rope.

2. Condition of the hook (hoising, opening, cracks, dents, etc)

3. Condition of the drum and drum grooves.

4. Condition of the brakes (shoe wear, touching of the rivets on the drum)

5. Alignment of bridge (screeching or squealing wheels are an indication of misalighment.)

6. Broken, cracked, or chipped rails of trolley or runway.7. Condition of limit switches.

8. Condition of drum controllers.

9. Condition of gears (grinding or sequeality may mean lack of lubrication or foreign material in gear teeth).

10. Condition of end stops of trolley and bridge runways.

11. Mechanical parts loosened by vibration (belts, screws, keys, covers etc.)

12. Bumpy right (worm wheels)

13. Warning or signal device.

14. Lubrication.

15. Condition of access ladders to cabin or bridge (loose, bent, or broken steps etc.)

Deflection Test


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MOBILE CRANES

Mobile cranes include locomotive cranes, crawler cranes, automotive cranes, and industrial truck cranes. All

these cranes have booms with load falls and boom hoists. In most instances, the rig slews on a turntable which

rests on a rail-road car crawler, or auto truck chassis. To prevent the boom from being dropped accidentally the

boom hoist should be operated by a worm drive. The boom hoist drum will then lock automatically when the

hoist is stoppped, and power will have to be used to lower the boom.

Every crane should have on it a capacity plate or a sign plainly legible to the crane operator, or rigger, stating

the safe loads at various radii from the centre-pin of the turntable. A plate can be mounted on the safe of the

boom near the hinge, with a pointer actuated by gravity suspended freely in front of it. The safe loads are

painted on thre plate, so that the pointed will directly indicate the safe load for any angle of the boom.

The operator must have safe access to an egress from his cabin or seat, regardless of the position of the crane

boom. He must have an unobstructed view of the load hook and the pointed of operation at all times. He must

also be able to see ahead of the crane when it is traveling, whether the motion of the chassis is forward or

backward.

if the crane is operated after dark, it should be equipped with clearance lights. Foodlights should illuminated

the scene of operation beneath the boom and lights mounted on the underside of the boom are recommended.

Loads should never be picked up when the weight supported by the chassis rests on springs over the axles, for

if would be difficult it not dangerous, to control the load. For instance, an automotive crane may have a high

boom swing to one side of the chassis when it picks up the load. As the strain is taken on the boom, the springs

on that side of the truck will compress, while those on the opposite side will ease up somewhat. As a result the

top of the boom will move outward, and the load, as it is picked up, will swing accordingly. Then the boom is

slewed to the other side of the chassis. When the load passes the centre of the chassis, the springs will take the

opposite action, the crane will tilt the other way, and the load will swing. To prevent this hazard, all load should

be taken off the springs of the vehicle by means of built-in jacks or blocks and wedges.

The boom must not be slewed too fast, because the suspended load will be swing outward by centrifugal force

and the crane may rock or even be upset and the load may swing an strike a person or object.

operating a crane on soft or sloping ground is dangerous. The crane should always be level before it is put into

operations.

When operating crane with the boom and a high angle, the operator should take care that the suspended load

does not strike the boom and bend the steel lattice bars on its underside. Bending these members will weaken

the boom, and when the next heavy load is picked up, the boom may collapse, Likewise, if the main members

of the boom are bent even slightly, the strength of the book may be materially reduced.

The hook must be centered over the load to keep it form swining while it is being lifted. The hooker, rigger and

everyone else must be in the clear before the load is lifted. A tag line should be used for guiding loads.

A heavy load should never be removed from a truck by hooking a crane to the load and then having the truck

pull out frm under it. If the load should prove too heavy for the crane, the crane will upset before the operator

can lower the load to the ground. The load should be lifted clear of the truck body, and the operator should

make sure that the crane can safety handle it before the truck is moved out from under it.

Except for very short distances, a crane should not travel with a load suspended from the boom.

The boom and cables of a crane should be kept away from all electric wires, regardless of their voltage.

Equipment should not be operated in such a manner that any part of it, includeing the load may reach within 2

m of electric lines or apparatus unless the power is shut off.

If the boom or cables accidentally come into contact with a wire, the operator should swing the crane so as to


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The carrying of passengers should be forbidden.

The width between forks should be adjusted to suit the load.

If a load is so bulky as to ohbstruct forward vision, the truck should be driven in reverse.

When carrying a load up a slope the truck should be driven forwards.

No one should be allowed under forks when elevated.

INSPECTION NORMS

FORKS

Forks should be regularly maintained and checked to ensure safety. They should be inspected at intervals of not more

than six months or whenever any defect is detected.

Surface Cracks :

The forks should be examined for cracks and appreciable wear. For this purpose its surface should be put into a state

which allows easy detection of cracks. Special attention should be given to heel and top hook. It surface cracks are

found the fork should be put out of service.

DeformationOn the new forks suitable marks should be provided on the neutral axis on the side of the fork for checking guage

length L2 as per the following table :

Form Arm Length Load Centre Distnce Guage Length H5

(L2+/-1)

800 400 550 395

1000 500 700 500

1200 600 1100 800

The forks should be checked visually for any deformation. The guage length should be measured within +/-

1mm. If it is found to exceed the value in the table by 2 per cent the forks should be put out of service.

Wear

After checking for cracks and deformation the fork should be tested with twice the rated load applied at load centre.

The guage length should be checked after removal of load. This load should be applied twice gradually without

shocks and maintained for 30 seconds. The fork should be checked before and after the second application of test

load. If an increase in guage length is observed the fork should be removed from service. Only the forks put out of

service for deformation should be repaired, and that too, the work should be done by the manufacturer.

CHAIN PULLEY BLOCKS

There are three general types of chain hoists; spur geared, screw geared (or worm drive), and differential. The

supergeared type is the most efficient. it will pick up a load with the least effort on the part of the person. The

differential type is the beast efficient. Screw-geared and differential hoists are self-locking and will automatically

hold a load in position. Since the spur-geared type is free running, it tends to allow the load to run iteself down.

Therefore, an automatic load brake, similar to that on a crane, is provided to hold the load.

Care and safe use of Chain Pulley Blocks

Chain pilley blocks are prevision made and should be treated with appropriate care. Do not drop chain pulley blocks

from a height.


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25

10. Extend the ladder side rails at least 3 feet (0.9mm) above the top landing.

11. Do not place a ladder close to electric wiring or against any operational piping (acid, chemical sprinkler system,

etc) where damage mat be done.

12. Ladders are for only one person at a time.

13. Do not place a ladder close to electric wiring or against any operational piping (acid, chemical, sprinkler system

etc) where damage may be done.14. Ladders are for only one person at a time.

15. Do not overload a ladder. Do not hit it.

16. Hold o with both hands when going up or down.

17. Always face the ladder when going up or down.

18. Never slide down a ladder.

19. Be sure your shoes are not greasy, or slippery before your climb.

20. Do not climb higher than the third rung form the top on straight or extension ladders or the second treat from the

top on step ladders.

21. Tools may be carried on a tool belt.22. Do not make-shift ladders, such as cleats fastened across a single rail.

23. Be sure that a step ladder is fully open and the metal spreader locked before you start to climb it.

24. Before using a ladder, inspect it for defects.

25. Never use a defective ladder. Tag or mark it so that it will be repaired or destroyed.

26. Do not splice or lash short ladders together. They are designed for use in their original length and are not strong

enough for use in greater lengths. Also most spkicing methods, particularly "on-the-job methods", and not

recommended.

27. Keep ladders clean and free from dirt and grease, which might conceal defects.

28. Do not use ladders during a strong wind except in emergency, and then only when they are securely tied.

29. Do not leave placed ladders unattended. Remember that children may be attracted to them.

30. Ladders shall not be used as guys, braces, or skids, or for other their intended purposes.

31. Adjustment of extension ladders should only be made by the user when standing at the base of the ladder, so

that the user may observe when the locks are properly engaged. Never attempt adjustment while user is stand-

ing on the ladder.

32. The length of a straight portable ladder is 30 feet (9mtr) or less. On two section extension ladders, the minimum

overlap is specified by standards.

33. Glass fibre ladders, as well as wood should be considered for use near electrical hazards.

WORKING ON ROOFS

Fragile roofThe common practice of walking along the purling cannot be relied upon. The best way to prevent

falls through such materials is to use roof ladder (crawling ladder). They should be at least 38cm wide and should

have cross battens at least 3.2 cm thick, fixed not more than 38cm apart. Safety belt should be used as an additiional

precaution. A permit-to-work system can help to ensure that men are not allowed to work on roofs without taking

appropriate safety measures.

In case of flat roofs it may be either the standard railing and toe-boards or a complete barrier to a minimum height of

90cm. For slopping roofs, the barrier may be in the form of scaffold boards extending to a minimum height of 40cm

above the roof surface and a guard rail at a height not less than 90cm or more than 120cm.

SAFETY WITH SCAFFOLD

Scaffold provides a convenient platform for work at heights and privides a safe means of access to all places where

any person may be required to work.


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Tubular welded frame scaffolds

1. Metal tubular frame scaffolds, including accessories such as braces, brackets, trusses. Screw legs, Ladders, etc.

shall be designed, constructed, and erected to safely support four times the maximum rated load.

2. Scaffold shall be properly braced by cross or diagnoal braces for securing vertical members together laterally,

and the crosses braces shall be of such length to automatically square and aling vertical members.

3. Panels shall be locked together vertically by pins or other equivalent suitable means.4. Drawings and specifications for all frames scaffolds over 125ft. high above the base plates shall be designed by

professional engineer.

Suspended scaffolds

Suspended scaffolds are platforms supported at more than two points by ropes suspendced form overhead outriggers

suitably anchored to the building. For raising or lowering the platform, a hoisting mechanism provided.

Suspended scaffolds should be designed with a factor of safety or four and shall never be overloaded. The outriggers

supporting the scaffold shold be of adequate strength abd be attached to the framework of the building with U belts

and anchor plates. The outer ends of the outriggers should extend beyond the outer edge of the scaffold platform by

about 30cm. they should be kept as horizontal as possible. Where counter - weights are used for preventing overturing,

they should be adequate factor of safety.

Wire ropes capable of taking at least 6 times the intended load should be used for supporting suspended scaffolds.

The upper ends of the ropes should be securely attached by shackles or U belts to the outriggers. The lower ends of

the ropes should be attached to the hoisting drum. The rope anchorage on the drum should be capable of sustaining

a load equal to the safe working load of the winch. Further, there should always be at least 2 dead turns of the rope left

on the last length of the rope left on the drum.

Suspended scaffolds should be slung as close to the building face as possible, allowing rooms for projections Wher-

ever necessary, they should be prevented from swinging by means of guy ropes.

The scaffold should be provided with handrails and toe-boards of dimension as detailed earlier. The space between

the top guardrail and toe-boards should be covered with 38 mm wire mesh of 16 guge wire. Overhead protection

should also be provided, if there is risk form failling objects.

Out rigger Scaffolds

These should not be normally used for general building constrcution, if other types of scaffolds can be conveniently

used. The outriggers should be passed right through the wall and be secured, adequately on the inner side. The

method of anchoring such scaffolds by inserting hook shaped member in between brick joints is dangerous and can

cause serious accidents.

Normally, the outriggers should not project beyond 2 meters from the wall. If it is necessary to exceed this limit, it

should be secured by anchor belts or other suitable means.

WORKING IN DEPTHS AND CONFINED SPACES

ENTRY INTO CINFINED SPACE - HAZARDS AND CONTROL

A. Entry into Confined spacesUnlike other accidents those arising from entry into confined spaces are pre-

ceded by a deliberate and conscious actthat it, the entry into the confined space. In case of work associated

with confined spacesm we can very well know where the accidents should any occur, will take place. We can

even know the persons most likely to be affected. Work in such cases is usually of a non-routine nature and this

we normally give more consideration there to. It is therefore possible to foresee probable causes of an accident.

Hence accidents associated with work in confined spaces are avoidable. What will be the severity of the injury,

if an accident occurs? The mishap in a confined space has a high probability of being fatal. It is, there fore, very

essential to set up safe working procedures. Such procedures should not only be devised, but enforced too.

They will not be effective unless they are enforced stricltly. Legal Requirements : Section 36 & 36 A of the

Factories Act 1948 prescribes the steos to be taken for work in confined spaces.

a) Rule 68 prescribed under section 36 lays minimum dimensions of manholes. They should be not less

than shoulder width of the person concerned plus 8 cms in legnth and 30 cms wide in case rectangular


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16/42

31

12. Flow VelocityLiquid velocity in the line should be restricted if the resistivity of liquid is high. This applies

specially if droplets of a second liquid phase are present. A limit on pipeline velpcities of 7m/s and 1m/s

respectively, for liquids without and with an immiscible component has been recommended. The much lower

limit for liquids with an immiscible component, such as free water, is due to the fact that in such liquids the rate

of charge generation can be up to 50 times greater.

FLAME ARRESTOR / SPARK ARRESTORFlame-arrestor

The flame arrestor or trap is a device used to prevent passage of a flame along a pipe or duct. most flame arrestores are

an assembly of narrow passages through which gas or vapour can flow. Flame arrestors are fitted on vents of storages

tanks containing flammable liquids, on pipe systems supplying fuel gas to burners, con certain pipelines conveying

flammable gases within the plant and flare stacks. Also used on, exhausts of internal combusion engine working in

flammable area.

Type of Flame-errestpr :

Crimped metal arrestor

Wire gauze Perforated plat

Wire pack

Packed bed etc.

Desirable Properites :

Arrestor should have high free cross-sectional area available for gas flow and low resistance to flow, freedom from

blockage, high capacity to absorb the heat and the flame, ability to withstand mechanical and thermal shock including

explosion.

Design :

Depned of the combusion properties of the flammable mixture and on the function and location of arrestor in the system.

The size of the aperture through the arrestor is determined by the quenching distance (some times covering both quench-

ing dia and critical slow witdth) of thr flammable mixture. The diameter of the aperture of an arrestor should be smallerthan the quenching diameter by atleast 50%. The quenching distance decreases as the temperature increases.

Flame arrestors are liable to blockage by dust, by condensate, by corrosion product. It is sometimes appropriate to

protect the arrestor with an expandable filter. A blocked arrestor should be cleaned by blowing air, or steam through

it or by washing and never by roding out.

Storage of Petroleum (Flammable materials)

Every tank shall be fitted with an independent vent pipe leading into the open air. The vent pipe shall be securely

supported and shall not be less than 4 meters in height and 4 meters from any adjoining land or any other facility in

which sources of fire are likely to be present. Vent pipe of anh tank shall nto be interconnected with the vent pipe of

another tank. The open end of every vent pipe shall be covered with two layer of non-corrodible metal wire guaze

having not less than 11 meshes per linear centimeter and shall be further protected from rain by hood.

Storage Shed - Storing Petroleum in drums/containers

The storage shed shall be adequately ventilated near the ground level and also near the roof. The ventilator shall be

provided with two layer of non-corrodible metal wire guaze having not less than 11 meters per linear centimeter.

Spark-arrestor

Transport on land by Vehicles carrying Petroleum

The exhaust shall be wholly in front of the tank or the load, as the case may be and shall have ample clearance from

fule system and combustible materials and shall not expose to leakage or spillage of the fuel.

The exhaust pipe shall be fitted with an approved spark arrestor (The open end of exhaust pipe shall be covered with

two layer of non-corrodible metal wire guaze hving not less than 11 meshes per linear centimeter)The muffler or silencer shall not be cut off from the exhaust system. The engine air intake shall be fitted with an

effective flame-Arrestor.


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33

The quality of illumination depends on three factors - diffusion, distribution and colour value. Regardless of the

quantity of illumination, its effects may be impaired because of the unenenness, the glare or the faulty direction of the

light.

Diffusion is the process of reflaction of light by a relfacting surface or of transmission of light through a translucent

material. This factor presents itself in the form of the problem of glare i.e. brightness of such a character as to cause

annoyance, discomfort, interference with vision. Glare and other factors are explained in the subsequent paras.Avoidance of GlareGlare is of two typesdirect and reflected.

Direct glare comes direclty from the light source to the eye and depends for its effects upon the position of the light

source in the field of view and on the contrast in brightness betwen the light source and its backgroubd. It can ve

avoided by

1. Reducing the brigntness of the light source (e.g. by enclosing the lamp in bowl reflactor)

2. Reducing the area of high brightness (e.g. by installing louvers below the light source)

3. Increasing the agnles between the source of glare and the line of vision and

4. Increasing the source of glare so as to lessen the contrast.

Reflected galre is that comes to the eyes as glint refection of the light source form some polished surface. It is caused

by a mirror image of the bright light source reflected from shiny or wet workplaces such as glass or plated metal.

Theses reflections distract attension, make important detail difficult to see and cause acute discomfort. It can be

avoided by

1. Changing the finish by having matt finish

2. Changing the task position or its surrounding

3. Using light sources of low brightness

4. Arranging the geometry of the installation so that there is no glint at the particular vie wins direction,

5. Providing supple monetary lighting.

Types of Light Sources :

Types of Lamp Luminous Efficiency Lumens/watt1 Incandescent 12 - 22

GLS or PAR Tungsten 10 - 13

Filament 13 - 18

2. Tungsten - halogen 20 - 27

(T - M) 14 - 22

3. Fluorescent Tube 75 - 95

50

With Tubes 62 - 66

Triphosphor 69 - 704. Mercury Vapour Lamps

High Pressure HPMV) 55

With fluorescence 35 - 50

MBI 63 - 72

5. Sodium Vapour Lamps

Low Pressure (SOX) 110- 140

High Pressure 95

Flurorescent lamps are good for medium ceiling and general uniform lighting where as for high bays HPMV lamps or

their combination with tungsten filament lamps are used. Generally fluorescent lamps are preferred because of theirhigher efficiency, longer life, low brightness, minimum glare and shadows, colour rendering close to daylight less

heat and linear form.


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35

ILLUMINATION

Thus illumination or lighting is an important working condition not only in factories but at all work places. Therefore

it should be effective and not poor.

Effects of bad lighting are direct and manifold because it affects our sight or visual perception. Bed light causes glare

shadows, darkness, eye strain and unhealthy eyes, restricted vision fatigue, accidents and lower output. Poor lighting

requies more time to see or distinguish objects. Glare and shadows cause eye-strain resulting in more chances ofaccidents. Therefore to increase safety, prescribed standard of accidents. Therefore to increase safety, prescribed

standard of illumination is the basic working condition.

Effect of Good Lighting are also direct and manifold, because if affects out sight as well as the object to be seen. It

helps two ways by better seeing for work performance and better environment. Better seeing condition causes better

dicrimination. Concertration, alterness and les fatigue. Better discrimination causes less spoiling and quick faulty

detection.

Sr. No. Area and Work-Room Minimum intensity of illumination in lux

1 Stockyards, main entrance and exit roads, cat-walks

of outdoor plants, coal unloading and storage areas 20

2 Passageways and corridors and stairways,

warehouses, stock-rooms for large and bulky 50

materials, platforms of outdoor plants, basements.

3 Engine and boiler rooms, passengers and freight

elevators, conveyers crating and boxing department,

Sotre-rooms and stock-rooms for medium and fine 100

materials, lockers rooms, toilet and wash rooms.

Ventilation & Heat Stress

(Ventilation is covered under 0856)

HEAT STRESSMEASUREMENT AND CONTROL

Problems of heat stress are very common in some industries such as Iron and Steel Mills, Glass and Ceramic Units,

Forge shoes, Foundries, Bricks and Tiles Factories. Thermoelectric plants, Cements, Coke ovens, Laundries, Mines

and many others. There are many work places in these units where artificial hot climates are deliberately created for

requirement of some processes. Whenever an individual is exposed to heat stress condition, there is a resulting strain

due to considerable changes in many physiological reactions such as 'sweat production', 'increased heart rate' and

'higher core temperature' etc. the greater the stress level the greater is the degree of strain experienced. It is well

known that prolonged exposure to excessively high temperature is a serious hazard to the health of an individual.

High heat stress distrubs the thermal equilibrium of the body. And consequently produces many adverse physiological

reactions in man. The condition becomes very alarming when high degree of industries heat combines with the

metabolic heat arising out of heavy physical work performed by the workmen, particularly during the summer months.

Work under such conditions not only produces undue strain and fatigue but also results in pregressive decline in

efficiency and productivity. It is, therefore, of prime importance to investigate this problem in order to ascertain and

quantify varous, contributory factors, and mitigate them, as far as possible, by suitable measures, In general terms, the

'Heat Sress' of any given working situation is considered as the combination of all the factors, both climatic and non-

climatic/person which lead to convective or radiative heat gain to the body or which limit of prevent the 'Heat

Dissipative Mechanism' of the body.

According to 'World Heath Organization' the 'Heat Stress' is the load of heat that must be dissipated by the body,m if

is to remain in thermal equilibrium, it is represented by the sum of the metabolic rate (minus external work) and thegain or loss of heat by convectin, radiation or the evaporation of sweat, these factors being governed by the tempera-

ture, humidity and movement of the air and by the temperature of the surrounding walls and objects. It is important to


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37

of discomfort or distress, and consequently the 'heat strain' developed among the individuales exposed to such

environment.

MEAUREMENT OF HEAT STRESS

Meaurement of Environmental (climatic) Factors (Stress Parameters)Heat has beem on record as a hazard to

man since biblical times. However, it is only in the late few decades that national means have been developed for

evaluating the stresses of hot environment identifying the contributing factors and prediciting the resulting physi-ological strain.

Air TemperatureThe air temperature is expressed in degree Celsiud (oC), or degree Fahrenheit (oF) and can be

measured with the help of mercury thermometers, thermocouples, thermostats and resistance thermometers. The

mercury thermometers are most widely used which are very simple, and more convenient other types, particularly

from the cost point of view, but very fragile, requiring care in handling.

Air humidityThe air humidity can be estimated from the absolute and relative humidity values. Wheres the absolute

humidity indicates the actual amount of water vapour in the air (expressed in grams of water vapour per cubic

centimeter) relative humidity is the percentile ratio of the amount of moisture present in the air and the amount that the

air could hold if saturated and at the same temperature.

PsychrometerInstrument used for measuring air temperature and humidity : The psychrometer basically consistsof two thermometers - a 'dry bulb' and a 'wet bulb' - over which are passes at a certain speed. Dry bulb thermometer

is just a liquid (most frequent mercury) in glass thermometer. Wet bulb thermometer is a similar one, but having its

bulb covered by cotton wick. The wick which covers the bulb of one of the thermometers is fully wetted wdith

distilled water. The psychrometer is placed at the point of measurement and air a certain speed is passed over the

bubls. When air passes over the thermometer bulbs, the reading in the dry bulb remains unchanged, while reading in

the wet buln decreses until equilibrium is attained. The air movement, which directly influences the evaporation of

water from the wick will have a cooling effect, thus decreasing the temperature in the wet bulb, referred to as the

'depression of the wet bulb'. The air velocity over the bulbs must be sufficient to ensure that equilibrium is reached

rapidy. The temperature values in both thermometers are read and recorded as 'dry bulb' and 'wet bulb' temperature

which are plotted on to a psychromatic chart and values for relative humidty, few point and absolute humidity can beobtained.

Sling Psychrometer (Whirling Hygrometer)This is a very simple instrument in which the thermometers are mounted

in a sling. The air movement over the bulbs is made by whirling the whole assembly. It is recommended to whirl at

about 60 revolutions per minute. Unsually one minute is enough to get the wet bulb thermometer to its lowest reading.

After checking the reading, it is adviscable to whirl a few more times, and check if the wet bulb temperature remains

the same, if it continues to fall, the process should go on until the reading is stablized.

Aspirating psychrometerThis instrument is basically the same as the sling psychrometer. However, the air is

circulated over the bulbs by means of an aspirator bulb to eliminate error from manual rotation. The same precautions

as for sling psychrometer should be applied.

Air MovementInstruments to measure air velocity are generally anemometers. The air velocity is measured from

the cooling power of the moving air. These are very useful from evaluation of heat stress because they also measure

non-directional, turbulent air movement which is important for because they also measure non-directional turbulent

air movement is important for heat transfer. Example-of instrument in this category are : (i) Kata-thermometer, (ii)

Anemotherm air meter (iii) Alnor thermoaneometer.

Kata-thermometerxs are mostly used for measuring movement of air.

Kala-thermometerThis instrument was designed by Dr. Willinam Hill Kala to measure the cooling capacity of the

surrounding air, which depends on its movement whether with a large bulb and an upper kata-thermometer is an

alchohol, (liquid) in glass thermometer with a large bulb and an upper reservior with two marks on the stem. These

instrument are made for different ranges (105o100oF, 130o 125oF, 150o140oF) and hence the slelection should

be made bearing in mind the thermal conditions before its use. The kata-thermometer can be used to evaluate the

cooling power of the air movement even for very low air velocitiesround ro below 0.25m/sec. (50fpm).


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39

source, the black globe temperature is considered instead of dry bulb temperature and the scale thus, constructed

effective temperature. (CET)

The ET/CT scales are modified depending upon the amount of clothing worn by the individuals such as 'Normal

Scale' and 'Basic Scale' which, can be constructed from two different monograms. The 'basic scale refers to 'men

stripped to the waist' and 'normal' to 'men who are fully clad in indoor clothing. The measurement could be made

by connecting the air temperature (DBT) or Globe thermometer temperature (in case it is more that DBT) and thewet-bulb temperature and noting the point at which this line intersects the family of curves running diagonally

upwards from left to right at the appropriate air-velocity. The scales are simple and widely used. However, the

scales are satisfactory only in mild heat stress provided that there is circumscribed range of relative-humidity. For

climate having relative-humidity of less then 40% the scales cannot be used. Morever, the scales exaggerate the

effects of high dry-bulb temperature in air movement of up to 3.5 m/sec. and underestimate the deleterious

impact of low air-movement in hot and himid environment. It is well known that widely different climateds

having same ET/CET values do not imposed the same physiological strain. Furthermore, the scales do not pro-

vide any allowance for different rates of energy expenditure.

5. Oxford IndexThis index of heat stress has been devised to assess the severity of hot humid coinditios of the

working place particularly where the ventilation is poor.This has been expressed by a simple weighting as follows :

WD = 0.15 d + 0.85 w.

Where WD = Weighted value, d & w are dry abd wet bulb temperature respectively.

Predicted Four Hourly Sweat Rate (P4SR)This index is based on the assumption of the amount if sweat that

would be perspired by a physically fit and acclimatized young man in the condition under review cover a period of

four hours. It takes into account the 'metabolic level' and 'type of clothing' in addtion to the climatic factors, unlike

other indices mentioned earlier. But this has the drawback the cumbersome monogrames are to be are to be referred

to, and thus lacks which is essential in a practical situation. Since the physical activity levels on the shop floor will

remain almost constant, we may make use of the simple indices like CET/ET or WBGT in our control programme. It

is thus evident that the heat stress indices like ET/CET, P4SR oxford, index etc. even though regarded as the useful

indices for the evaluation of stress have inherent shortcomings and limitations. As a matter of fact some of them

require expensive equipment and / or are difficult to determine in industrial work. An index which has received much

attension in recent years, and has been officially adopted by some countries, is the 'Wet Bulb - Globe Temperature

Index'. It also has limitations, but has the difinite advatages of being very easy to determine and of requiring simple

and inexpensive equipment.

Wet Bulb Globe Temperature (WBGT) IndexIt embraces in a single value the effect of 'radiation' and 'ambient air

temperature' and 'humidity'. It is the weighted value of wet and dry bulb temperature and globle thermometer readings,

calcilated using temperture measurements alone, thereby eliminating the need to measure air velocity.

The wet bulbglobe temperature index, was intially developed to provide a simple method for the assessment of heat

stress among the military personnel. The basis for this index is that the wet Bulb-Globle Temperature (representing

the environmental heat load) is combined with the work load (representing the metabolic heat load) by plotting the

values of both parameters on a co-ordinate system and evaluating the resulting point in relation to curves established

according to the concept of prescribed zne, as described by Lind. For continuous exposure over 8 hours, the limiting

curve is the 'Upper Limit of the Prescriptive Zone (ULPZ) Line' This curve is such that it represents the upper limit for

combination of environmental conditions and work loads that do not cause an increase in the core temperature to

above 38oC in 95% of average acclimatized individuals. In the 'Prescriptive zone' the deep-body temperature is

determined only by the workload (physical activity) and is practically independent' from the environment while in

the 'Environmental Driven Zone' the deep body temperature becomes sensitive to small changes in environmental

climatic conditions.

Equipment : The instruments required for the determination of the WBGT are :

Dry Bulb Thermometer (for measurements outdoors in sun shine only) - ta


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41

ta

= dry bulb temperature

k = coefficient, whose value varies.

(Value for K is related to the clothing or the type of skin).

a) For outdoor exposures with solar load : Miner has prososed a simplified formula (which has been adopted, for

instance, by the American Conference of Governmental Industrial Hygienists (Threshold Limit Values) as Fol-

lows :WBGT = t

nwb+ 0.2. t

g+ 0.1

n

b) Indoor exposures or outdoor exposures with no solar load

In this case, K takes the value of 1 and the equation becomes :

WBGT = 0.7 tnwb

+ 0.3 tg

c) Time-weighted average WBGT (WBGTtwa

): When environmental conditions very significatly, or the workers,

move through places and jobs that cause different levels of heat stress, a time weighted averge WBGT should be

calculated as follows :

WBGTtwa

= (WBGT1) t

1+ (WBGT

2) t

2+ ....+(WBGT

n) t

n

t1

+ 12

.............tn

WBGT1

= WBGT determined for situation or location 1

WBGTn

= WBGT determined for situation or location n

t1

t2

...................... tn

= time spent respectively, in location 1, 2 ..........tn

Time weighted average WBGT values must be calcluated on an hourly basis, if the heat exposure is continuous, and

not for an 8 hour period. A very extreme heat exposure for over 1 hour might cause health impairment. An inappreciable

exposure for the rest of the shift might bring the calculated time weighted average WBGT to a value even below the

permissible level but damage would already have been done to the worker's health./ for intermittent heat exposure,

this time weighted average can be calculated on a 2 hourly basis.

In some cases, where the worker is exposed to a wide and variable range of environmental conditions, it may be very

difficult to determine a meaningful time weighted average WBGT.Permissible Heat ExposureThe permissible heat exposure threshold limit values recommended for use in the

United States are given in following table :

Permissible heat exposure threshold limit values

(Values are given ino c WBGT)

Work-Rest regimen Light Work load Heavy

Mode

Continuous work 30.0 26.7 25.0

75% work 30.6

25% rest each hour 30.6 28.0 25.9

50% work 31.4

50% rest each hour 31.4 29.4 27.9

25% work

75% rest each hour 32.2 31.1 30.0

CONCLUSIONThe determination of the WBGT index is very simple and relatively inexpensive. The items of

equipment required are usually found on the market. Auxiliary personnel can be trained to carry out the measure-

ments but must be supervised by an experienced professional.


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5. Provision of Cold Drinking WaterThe workers should be educated and advised to take plently of cold water

very frequently to replenish the fluid loss due to heavy sweating during work in heat. Provision should, there be

made foe easy available of cold water very close to shop floors.

6. Selection CriteriaThe heat stress is likely to impose undue stress on the cardiovasculasr system and thus

workers with strong body build and high levels of physical fitness should be selected for hot opertions. Persons

reported to be suffering any cardiac diseases should be correlation between the 'physical fitness levels' and 'heattolerance limits'. Performance decrement was reported more among the workers with relatively low levels of

fitness than those with high degree of fitness.

7. Periodical Check-upFrequent periodical check-up is also necessary to asses the physical fitness levels of

individuals exposed to hot environment to ensure whether they are still fit to work under such environment.

8. Plant Designing covered in 0857

House keeping covered in 0856

Ventilation covered in 0856

Noise covered in 0856

Electrical Hazards covered in 0855.

SAFETY VALVE, RELIEF VALVE AND RUPTURE DISC

Functionally the operation of a safety valve and relief valve is more or less similar except in that in case of relief valve

the over pressure on the upsteam side of valve actuates the mechanical device which opens the valves disc. The

opening being in proportion to the pressure increase above the set valve. Whereas in the case of safety valves the

valve has repid opening nornamlly to full lift with a pop action and does not close until the pressure ipstream reaches

value coresponding to the set closing pressure, which may be much lower than set opening pressure. In order words

safety valve remains open for a specific range unlike the relief valve which opens in proportion to the over pressure.

Normally the safety valves, used for steam, gases and vapours, 'where as relief valves are used on unfired pressure

vessles, air compressors, water heaters, manifold, pipelines etc.

Rupure disc is a thin piece of metal incorported into a pressure system to prevent damage that could result from an

excessively high-pressure peak. Discs can be flat, prebulged in either direction, or corrugated in the form of bellows.

Rupture discs are provided in certain pressure vessles where the chances of steep increase in rate of pressure rise

exist. The rate of pressure rise may be of the order of milli / microseconds. This dics comprises of a membrane

disigned to burst open at the set point. They rupture when a stress imposed by pressure exceeds the strength of the

disc pressure foces the disc against a knife-edge or pressure sensor indicates the pressure level of the protected vessel

has exceeded a specified level. The disadvantage of the disc is that the system, once opened, empties and is inopera-

tive until the passage created is closed by replacement of the disc. Fot this reason, a disc is often used in conjuction

with a safety or relief valve, which provides the primary relieving capability. If this is inadequate, the disc will rupture.

Importfection in manufacture, installation, or caused by corrosion can cause the disc to fail prematurely. In many

instnce a rupture disc is provided as a back-up safety device for primary safety valve.

CONVEYORS VARIOUS TYPES SAFETY ASPECTS

A horizontal inclined or vertical device for moving or transporting bulk material, objects, packages, innerpath ore

determined by the design of the device and having points of loading or discharge, either fixed or selective. Skip hoists

and vertical reciprocating conveyors are also included in this definition.

Types of Conveyors :

1. Belt conveyors

2. Slat Conveyor

3. Apron Conveyor

4. Flight Conveyor

5. Chain Conveyor

(a) Overhead


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8. Bucket Conveyor :

They are of three general types :

(a) Bucket Elevator type

(b) Gravity dischargre conveyor

(c) Pivoted bucket type

A permanent foot walk should be provided along-side a conveyor that hoists material and carries it over bins.9. Shackle Conveyor :

A shackle conveyor consists of a chain type of conveyor with suspended shackles evenly spaced along the line

for conveying poultry or meat products.

10. Pneumatic Conveyor :

This is an arrangement of tubes and ducts through which solid objected like mail, cash, grain, dust or similar bulk

materials of small items are transported by means of compressed air or vaccum. Compressed air injected into the

tubing system pushes the cylindrical cartridge, containing such sold objects forward at a relatigely high velocity.

To convey bulk material, the air mixes with the materials and makes it flow rather like a liquid through the piping.

When materials have dust explosion hazards, the air velocity should exceed the critical velocity for flame propagtion

and the equipment must be boneded electrically and grounded to prevent static electricity being an lgnition

source.

11. Aerial Conveyors - Cable supported syste.

Types are : (a) Cable -way, one span.

(b) Tramway - one or more spans.

These are used in large construction work to transprot material form one point to another, e.g. for carrying coal

or ore. The principal hazards are failling material injuring to workers inspection and oiling the cables and car-

riages and misunderstainding the signals.

Wherever workmem have to work undermeath the conveyor a covered passageway should be provided. Heavy

wire screen suspended under the conveyor and wide enought to catch the failling material can also be provided.12. Portable conveyor :

They could be of belt, flight, apron or fixed bucket or other types. They are as inclined portable hoists and a pair

of large wheels for loading fail and road cars and trucks with bulk material and for raising construction materials,

from one elevation to another.

13. Gravity Conveyor :

Natural force of gravity is depended upon for their operation, hence, necessary safe practices are often disre-

garded. Although they are not power driven, serious accidentss can happen.

If an employee climbs upon such a conveyor (spiral chute) to release a blockage, he may slip on the rollewr

below or be knocked down, should the jab be sudenly released on him.

They are of two types :

(a) Chute Conveyor (b) Roller Wheel Conveyor

(a) Chute Conveyor

They are used to lower packing cases, cartons and crates from one floor to another of from side walks to a

basement.

(b) The inclined chute may be straight or (18 deg. to 30 deg.) with a vertical curve of a large radius to deliver

packages on to the lower floor without impact or damage.

(b) Gravity Roller or Wheel Coveyor

They are similar to chute conveyor excep that the angle of stops is much less (2 to 4 per cent). They can be

used to convey packages for considerable distance on floor. If rollers or wheels are placed radially insteadof parallel, course of the travel can be changed from a straight line to a curve.


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10. Workers must wear tight fitting clothing with safety shoes. If galleries are dusty, approved goggles and if neces-

sary dust respirators should be used.

11. Materials must be carefully placed on a conveyor so that they do not fall from the conveyor and strike and

workers around.

COLOUR CODE FOR THE IDENTIFICATION OF PIPELINES

(IS 2379)

Important features :

a ScopeCovers the colour scheme for the identification of the contents of pipelines carrying fluids in industrial

installations.

b IdentificationThe system of Colour codig consists of a ground colour & colour bands.

c Where the ground colour is not applied throughout the entire length, it shall be applied near valves junctions,

joints , service appliances, bulkheads, wall etc.

d When colour bands are superimposed on the ground colour, the ground colour shall extend sufficientally on both

sides of the colour bands to avoid confusion.

e Colour bands shall be arranged in the sequences given.

f For insulated pipe, the ground colour shall be applied on the metal cladding or on the pipes of material such as

non-ferrous metals, austenitic stainless steel, plastic etc.

g When it is desired to indicate that a pipelines carries a hazardous material, a panel of (Slightly Radioactive

Hazards, Highly Rdioactive Hazards, Other Hazards) shall be superimposed on the ground colour at suitable

intervals.

h LetteringLettering is recommended for chemical industry for the porducts not covered in the Table given

below. For steam, temperature and pressure shall be indicated after colour indication, by lettering.

i Direction of flowWhere it is required to indicate the direction of flow, arrows or letters may be painted near

valves, junctions, walls etc & at suitable intervals along the pipe, in a manner best suited to local conditions.

COLOUR CODE

(1) General Services

CONTENTS GROUND COLOUR FIRST COLOUR BAND SECOND COLOUR BAND

Cooling Sea green French blue

Boiler feed water Sea green Gulf red

Condensafe Sea green Light brown

Drinking Sea green French blue Signal red

Treated Sea green Light orange

Fire water Fire red Crimson red

Chilled water Sea green Black Canary yellow

Sprinkle & Hydrant Sea green White Signal red

Water

Waste water Sea green Canary yellow Signal red


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V) HYDROCARBONS


Propylene Dark admiralty gray Brilliant green

Ethylene glycol Gulf red

Benzene Canary yellow

Butadience Black Acetone Black Canary yellow

Methanol Deep buff

Naphth Light green Black

VI)ACIDS


Phosphoric acid Dark violet Silvery gray

Hydrofluoric acid Signal red French blue

Sulphuric acid Brilliant green Light orangeNitric acid French blue

Hyrochloric acid Signal red

Acetic acid Silver gray

VII) CHEMICALS


Brine Black White

Lime Smoke gray White Canary yellow

Carbon sulphide Black Light orange Strong caustic Smoke gray French blue White

Sodium sulfide Black Brilliant green Canary yellow

Sodium carbonte solution Dark violet Jasmine yellow

VIII) MEDICAL GASES


Air Sky blue White Black

Cyclo propane Canary yellow Light orange

Carbon dioxide Light gray Ethylene Dark yellow Signal red

Helium Light brown

Oxygen White

Ox & CO2 mixture White Light brown

Nitrous oxide French blue Signal red

Nitrogen Black

Vacuum Sky blue Black


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Kerosene fired oven have not pilot arrangements. Piece of cloth or cotton waste soaked in kerosense is tied to

one end of a long stick and lighted. Kerosene and air is slowly released and is lighted with the stick.

It Kerosene and air is not slowly released there will be a back fire.

Similarly the lighting device should not be allowed to go off. Otherwise the kerosene and air will get accumu-

lated and later on while lighting there may be an explosion.

To overcome this a gas burner should be provided for lighting the ovens. Job Safety Training to the operator's.10) While loading and unloading cores on core baking oven hazard of cores falling down. Employees will be

exposed to heat, smoke & fumes, inform red rays and falling of hot sand on head. While handling core boxes,

core plates & cores fall on feet & toes. Training in safe methods of handling to the employees, asbestos hand

gloves or aluminzed hand gloves for handling hot cores, light green goggles, fume mask, caps and safety shoes

to be used.

11) Outlet & exhaust arrangement to be provided for smoke and fumes generated in core baking ovens.

12) Heating of core with portable gas burners to be done on tables and not on floor. Proper area shoul be provided

and heating should be done in that area. This area should be kept clear of combusible material.

13) Burners, hoses and gas line valves should be checked and maintained once in fortnight. Burners should be

lighted with electronic lighters, to be fixed near heating tables.

14) Tongs should be used for feeding lead and other material to the container used for heating the same. Splashes

of molten lead may cause burn injuries.

15) Heating of cores with gas burners should never be done in closed rooms. In case of gs leakage the room will be

fill of gas, fire and explosion may take place as there will be no ventilation.

16) Painting of cores should be done in proper paint booths and exhaust arrangements should be provided. Paint

booth should be cleaned regularly and accumulated paint removed.

17) Hoists, trolleys, wire ropes etc, should be visially checked by the users, for any defects, before taking them into

use.

18) Industrial waste, spilled sand, cotton waste, scrap, broken cores should be removed from core room regularly.19) While making cores on hot end shell core making machine, vapours from resins will be generated. Those

vapours are only a nuisance because the concetration needed to produce toxic effects cannot be usually toler-

ated by men.

20) Employees making cores by hand may suffer from dermatitis due to contact with core oil and sand. Washing

with soap and water will prevent this.

MOULDING

A) Operations

Sand plant prepared and supplies blended sand for making the moulds. Sand in fed to sand mixer through & con-

veyor. After the sand is blended it is supplied to moulding machines. Moulds are made on moulding machines. Some

moulds are made by hand also. After drag (borrom mould) is ready it is placed on the mould car conveyor. Coresor

core assemblies are place in position. Drg in then closed by cope (top mould). After placing the cope of drag clamps

are put. (to avoid metal run out during pouring). In some foundries the moulds are placed on floor for pouring.

Thereafter, the mould moves forward to pouring stage for pouring. Pouring is done manually by ladles travelling on

gantry. Small ladles (crucibles) are handled manually. Bigger laddles are handled by crane.

After pouring, the mould is allowed to cool down and the castings are knocked out on the knock0-out machines.

Some castings are knocked out manually. Some time the hot castings are also kncoked out.

From knock out stage, castings are taken for shaking out operation and then carried to fettling section for further

finishing. After knocking out of the castings from mould box, the sand is reprecessed. It falls on the return sand

conveyor below the knock out machine and passes through the magnetic pulley for separation of metalic pieces from

sand. Then through the return sand elevator and a small conveyor the sand is stores in sand bunkers. From bunkers

the sand falls on mixed sand conveyor where fresh sand is also added and then through a screen and mixed sand

elevator the sand is stored in surge hoppers. Sand is fed to sand mixers from surge hopper through a conveyor.


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MELTING / POURING

a) Operations :

Receiving of scrap and coke, breaking of scrap and coke, handling of scrap and coke on wheel barrows to charg-

ing area, filling up of the skip charger with scrap, coke and additive, firing of cupola, charging of cupola, slag

discharging, tapping of molten metalin the ladles, closing of cuploa tap hole with clay bots. Handling of molten

metal ladles on gantry to different pouring bays, manual handling of small ladles (crucibles). Pouring, dropping ofcupola, cupola lining.

Feeding of molten metal from cupola through ladles to electric induction furnaces for super heating. Lighting the

burner of cupola recuperator, starting cupola blower. Cooling down operations, removal of slag and waste.

b) Machines used :

Cupola charges, Cupola Blower, cupola Recuperator, Cupolas, Electric Induction Furnaces and ladles.

c) Hazards in Melting and Pouring Operations :

1) Employees enganged in breaking of scrap and coke will be exposed to flying chips and cuts, failling of scrap

on feet & toes while removing the same from pile. Safety goggles and safety shoes to be used.

2) Scrap to be checked properly before charging for any moisture or water accumulation. Cylinders, cans and

drums to be broken to avoid explosion risk.

3) While leading the scrap and coke on wheel barrows for carrying to charging area, it falls on feet & toe due to

overloading, tilting of wheel barrows due to imbalance or uneven floors. Overloading to be stopped, flooring to

be maintained in good condition, safety shoes to be used.

4) Cupola charget pit and charing area to be properly fenced to avoid injuries due to falling of scrap pieces while

charging.

5) Hazard of cupola getting clogged due to cloggig of tap hole or while dropping. Vibrating device to be used or

hot air to be blown inside the cupola.

6) Slag tap hole to be properly fenced, to avoid slag sparks flying in all directions.

7) Molten metal spout

safety in engineering paper iii

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