Electrical Works
Wholehearted support and commitment of every employee is essential to execute the work following all safety precautions.
Obtaining proper line clear from all possible sources of supply shall be taken and the following precautions are to be taken.
1. Till a Line Clear (L.C.) is received from all sources every line or equipment shall be treated as live.
2. Hang “Danger” boards at all strategic places to ensure safety at work spot 3. Where there is a risk at places of work cordon off the area from unauthorized persons
4. Explain the area which is safe to work and ensure that every employee in your team has understood the same.
5. Nominate one among the team exclusively to reap a close watch and ensure that every person in the team is safe.
6. Earthing is to be provided on both sides of the work spot before proceeding with the work.
7. All safety rules are to be followed till entire work is completed.
8. Insulated earth rods with clamps shall be used and the person using the earth rods shall keep safe distance from earthing wires.
9. Examine earth rods and every safety appliance before using 10. No person shall be allowed work if he is under the influence of alcoholic drinks under inebriated condition.
Safety Precautions
1. Workmen should not wear loose dress
2. Workmen shall be properly trained
3. All lines shall be treated as live till proper line clears is received 4. Adequate clearance between lines on which work is being done and other live wires shall be ensured or line clears taken on those lines also.
5. Lines / equipment shall be earthed before proceeding with the work 6. Display of all precautionary boards such as Danger Boards shall be ensured by both persons issuing / receiving line clear
7. Dresses shall not have metal buttons.
8. Shoes with metal nails etc shall not be used and one those with rubber bottom shall be used.
9. Items made of metal like chains of wrist watch, key bunches, rings, bracelets shall not be used while on work
10. Tools should not be thrown at each other while on work 11. Use a proper tools for each job
12. Rubber gloves / gauntlets shall not be used for works of voltage class 33 KV
and above.
13. Rubber gloves / gauntlets can be used only when
♦
Line voltage is 5 KV or below
♦
While earthing
♦
Opening of AB switches
♦
Using portable telephones
♦
Working on street light fittings
14. Use of safety belts while works on poles / platforms above 3 meters height shall be properly understood.
♦
Proper way of use of belt
♦
Proper way of removing the belt
♦
Proper way to get up or get down the pole and also the way to change direction
Ladders:
1. Ladders shall be based on firm ground.
2. Always face the ladder and use both hands
3. Not more than one person shall use the ladder at a time.
4. Another person shall be kept to watch the ladder position 5. Ladders shall be normally used with a slope of 45 degrees.
Tools & Appliances
1. Proper tool for proper job. Every tool or appliance shall be in good working condition (ex. Slings, pulleys, chain block etc) 2. Non working tools / appliances shall be permanently discarded 3. Damaged pipes, spanners, hammers shall be discarded.
4. Use always insulated pliers & screw drivers (only on LT) 5. When more than one LT circuit is laid from a transformer, ensure that street light circuits are also separate. Better take LC on both CT circuits 6. “Double feeding point – Danger” board shall be displayed when supply from two sources is available
7. When loads on one transformer are transferred on to another, it shall be noted in the log book and intimation given to duty staff.
8. Minimum distances to be maintained while working (Minimum safety working clearance)
12 KV
-
2.6 Meters
36 KV
-
2.8 Meters
72.5 KV -
3.1 Meters
145 KV
-
3.7 Meters
245 KV
-
4.3 Meters
420 KV
-
6.4 Meters
80 KV
-
10.3 Meters
9. Keep safe distance from rotating equipment. Do not attempt to handle them while working
10. Avoid haste while working
11. Avoid joking while working
12. Do not work while feeling exhausted
13. Mind your personal safety and do not depend on others 14. Ensure all three blades of AB Switches are open before working 15. Loose connections can cause fires
16. While earthing, other personnel shall be 12 to 15 feet away.
17. Clearance above ground of the lowest conductor Voltage description
Across the Along the
street
street
(Meters)
(Meters)
Low and medium voltage lines
5.8
5.5
High voltage lines
6.1
5.8
Voltage description
Else where than the street, clearance
in meters
Low, medium and high voltage lines
4.6
upto and including 11,000 V if bare
Low, medium and high voltage lines
4.0
upto and including 11,000 V if
insulated
High voltage lines above 11,000 V
5.2
Precautions to be taken before providing temporary earth 1. Ensure that the line / equipment is not live 2. Only authorized person shall provide temporary earth or remove it 3. Insulated wires for providing earthing shall be firmly connected to earth electrode before touching or equipment
4. Earth wire should not be close to other live wires 5. Provide temporary earth on both sides of work spot 6. While disconnecting ; the earth rods shall be first disconnected from line /
equipment
7. Rubber gloves / gauntlets shall be worn by the person providing the temporary earth
8. The person earthing shall be at a lower level then the line / equipment being earthed.
9. Other workmen shall be 6 meters away while earthing 10. The earthing shall not be disconnected till the whole work is completed and cleared of men and materials.
11. While working on a 3 phase line earth all the conductors even if work is being done only on one phase
12. While one or more workmen are working at a height others should be away so that tools or materials dropping cannot hurt them.
13. Every employee shall watch his counterparts that safety procedures are being followed
14. Whenever a switch is found open check up why it is kept open, examine the parts of lines & equipment it is controlling and ensure that it is safe to recluse before doing so.
15. Ensure that your hands or clothes are not wet while earthing / working 16. It is unsafe to check whether a line is live or dead with bare hands or other methods
Line Clears & Precautions
No workmen shall get up a pole or work on any lines or equipment unless he is specifically authorized to do so.
Line clears can be issued or received only by authorized persons.
When it is not possible to receive or return line clear in person; the same can be done over telephone but clear identity by way of voice and also a code shall be followed.
While issue of line clear
1. Switch off supply and ensure that the work spot where L. C. is requisitioned is disconnected from all possible sources of supply.
2. Ensure personally that all blades of all operating switches are open 3. Discharge the line / equipment using discharge rods properly earthed and by wearing rubber gloves / gauntlets.
While returning line clear
1. Only the person who obtained the line clear can return the same 2. The person returning the line clear shall ensure that the line / equipment is clear of all men, materials and earthings
3. Inform all colleague workmen that his returning the LC and that it is no more safe to work on that line / equipment
4. Person receiving back the LC shall ensure that no more LCs are pending return 5. The entire team of workmen shall stay back till the line / equipment is recharged and can leave the work spot only after re-charging Checklist before working on line
1.
Have you undergone safety training?
2.
Have you opened the A.B. Switch feeding supply?
3.
Are the LT fuses removed?
4.
Are cables at Dn box away without touching it?
5.
Have you provided temporary earths at work spot?
6.
Are you wearing gloves?
7.
Did you check earth rod in place?
8.
Are you wearing helmet/
9.
Have you taken the safety belt with you?
10.
Are you confident of getting up the pole?
11.
Did you ensure that all other workmen in your team are following all safety precautions?
Safety Precautions for Protection against electric shock
Due to heavy gales and cyclonic winds, overhead lines are more prone to breakdowns, due to snapping of power conductors etc. Public can help the power utilities and safeguard themselves by following the measures explained below.
♦ Unauthorized persons shall not attempt replacement of transformer fuses
♦ Other than utility employees shall not try to replace street lights or set right service wires
♦ Inform nearest utility office if loose or hanging wires are noticed
♦ While drilling bore wells ensure that the casing pipes do not touch live wires while they are being lifted up.
♦ Do not go near the Distribution transformers
♦ Do not touch low lying or snapped conductor
♦ Do not lean against electric poles
♦ Do not stand beneath overhead lines while heavy winds are blowing Appendix
List of testing instruments to be provided in mines A. At colliery level
1. 'Megger' type insulation tester up to 1000 volts; 2. Tonga Meter; and
3. Volt Meter.
B. At Area level
1. H.T. Megger up to 5000 volts;
2. Earth Leakage Relay Testing Set;
3. Earth Resistance Testing Set;
4. Relay Testing Set;
5. Volt meters and Ammeters of different ranges; 6. Transformer Oil Testing Equipment; and
7. Cable Fault Locator.
(Cir. 67/1973 & Cir. 47/1974)
Accidents & Main Reasons
♦
Unauthorized persons working on lines / equipment
♦
Working without using safety appliances
♦
Working without obtaining proper line clear
♦
Working without proper instructions from superiors
♦
Wrong instructions from person who received the line clear
♦
Negligence, carelessness, haste and overconfidence
♦
Lack of knowledge on feeding arrangements
Dumper Brake and Test Procedure
A brake is a device for slowing, stopping, or holding an object. The first brakes were brake shoes operating directly on wheels. From this simple beginning has evolved the most complex braking systems. The first air brakes were introduced in 1918. In the year 1925 four wheel brakes were introduced on trucks, and the internally expanding type was introduced by 1930. In the late 1930s hydraulic brake was introduced. Air cooled disc type brakes were introduced in the 1990s on heavy duty dumpers/trucks. These units were combined with electronically controlled antilock air brake systems in order to reduce the possibility of jackknifing.
In Opencast mines most of the accidents occur due to wheel trackless vehicles. Analysis of Fatal Accidents in Opencast Mines during the year 1981 to 1987 shows that 70.4% of accidents were caused by dumpers/trucks.
In the Year 1992, Fatal accidents due to wheeled trackless transportation machinery caused 26.4% of all fatal accidents in metalliferous mines and it contributed 34.6% of all fatal accidents in opencast and surface operations.
16.7% of the accidents occurred due to failure of brakes.
In the Year 1993, 13.46% of all fatal accident in coal mines was caused by wheeled trackless transportation machinery. This cause contributed to 38.18% of all fatal accidents in opencast and surface operations. 62% of the accidents by wheeled trackless transportation machinery were caused by trucks.
In the Year 2006, Fatal accidents due to dumpers in coal mines is 14.6 %
and due to trucks and tankers 2.4%. The corresponding figure for non-coal mine is 16.1 % and 12.9 %. In particular, due to dumpers fatal accidents in MCL during 2007 is 03 out of the total 04 accidents, which is 75% of the total accidents.
Braking system of dumpers in use in MCL:
Braking system of a dumper is the key safety feature, which needs attention right from maintenance crew to operator to supervisors. The braking system of BEML LW35 /HM1035 is of air over hydraulic – master cylinder-power cluster with expandable brake shoe type which was not a full proof braking system. Now MCL is phasing out all these 35T dumpers having expandable shoe type brake.
Braking system of Hindustan 773B Series II dumper: - Front brake:- Air –
over – oil actuated, caliper disc type. Operator can switch front brakes out of service system when not needed. Braking surface is 1394 sq.cm. Rear brake:-
Caterpilar oil- cooled, air – over – oil actuated disc brakes provide both service
and retarder braking. Sealed from dirt and water. Individually replaceable as units. Braking surface is 61264 sq. cm.
BEML 210M:- Service brakes:- Front:- a) type - Dry disc caliper type. b) actuating system- Hydraulic
Rear:- a) type – Oil cooled multiple disc. b) actuating system- Hydraulic Secondary brake:- Either front or rear brakes independently meets the secondary braking requirement. Actuation is automatic, a manual control switch is provided.
Parking brake:-Parking brake is disc type with actuating system of spring loaded, hydraulically released and will automatically apply whenever hydraulic pressure drops.
Retarder:-Oil cooled wet multiple disc brake actuated through foot control valve.
Separate foot control s provided in the cabin to actuate oil cooled wet multiple disc brakes on rear axle. The same can be operated to control/ retard the speed of the equipment while descending grades.
Safety tips related to brakes:-
Loading – while truck is being loaded, operator should stay in cab of truck.
Apply brake lock during loading operation.
Hauling – Maintain a safe distance when following another truck. Never approach another truck from the rear, in the same lane, closer than 15 mtr.
When approaching on a down grade, this distance should be no closure than 30 mtr.
Before starting up or down a grade maintain a speed that will insure safe driving and provide effective retarding under all conditions. Refer to speed
/ grade declare in operator cab.
Do not stop or park on a haul road unless unavoidable. If you must stop, move dumper to a safe place, apply parking brake, block wheels securely and notify maintenance personnel for assistance.
Dumping – when in dump position, apply wheel brake lock and move selector switch to “neutral” position.
Parking – if parking dumper in other than designated parking area is necessary, select a level area, apply parking brake and block wheels front and rear. Do not use brake lock as a parking brake.
Testing – Operate each of the dumper brake circuits at least twice prior to operating and moving the dumper. These checks should be include individual activations of the service brake, parking brake, and brake lock with the engine running. If any application/release of any brake circuit does not appear proper, or if sluggishness is apparent on application/release,
shut the dumper down and notify maintenance personnel. DO NOT operate dumper until brake circuit in question is fully operational.
Check parking brake periodically during shift. Use parking brake for parking only.
Brake testing: (Abstract of DGMS tech Cir No. 3 of 1981-) (1) At least once in two weeks the brakes of the truck, dumper or any such other vehicle should be tested as indicated below :
(a) Service Brake Test—The brake shall be tested on a specified gradient and speed when the vehicle is fully loaded. The vehicle should stop within a specified distance when the brake is applied. The specified stopping distance shall be obtained from the manufacturer of the vehicle.
(b) Parking Brake Test— The parking brake should be capable to hold the vehicle when it is fully loaded and placed at the maximum gradient of roadway which is permitted for a period of at least ten minutes.
BRAKING TESTING METHODS AND PROCEDURES
All dumpers must undergo the braking performance tests required. Such tests must be conducted in accordance with the following methods and procedures.
A) General
1) All tests must be conducted with applicable braking systems fully charged.
2) Dumpers will be tested under the condition that it is loaded to manufacture’s gross machine weight rating and distribution.
3) All dynamic stopping tests must be conducted from 32 KMPH.
4) Stopping tests shall be conducted with the transmission in the gear range commensurate with 32 KMPH testing speed.
5) Auxiliary retarders shall not be used in the test unless the retarder is simultaneously activated by the applicable brake control system.
6) Stopping distance shall be measured from the point at which the brake control is applied to the point at which the machine stops.
B) Services and emergency braking system
1) Service and emergency dynamic braking tests shall be conducted on a level (less than 1 percent grade in direction of travel and 3 percent at right angles to travel) clean swept dry surface. The course length will be sufficient for accelerating from 0 to 32 KMPH and providing a stopping distance equal to 1½ times that shown for emergency braking system.
Static service brake holding tests shall be conducted on the greater of 15
percent grade or maximum grade of intended travel.
2) Service and emergency braking system shall have the following stopping capabilities in meter when travelling at 32 KMPH.
BRAKING DISTANCE
Carrying
Braking
Remarks
Sl.No. Description
capacity
Weight in distance
in
Te
meter
1
LW35(Empty)
35Te
22.81
17.98
Speed 32 KMPH
2
LW35 (Load)
35Te
54.56
22.55
and
grade
as
3
210M (Empty)
50Te
40.96
17.98
described above.
4
210M (Load)
50Te
90.85
22.55
5
HM773B S-II(Empty)
50Te
38.66
17.98
6
HM773B S-II(Load)
50Te
84.02
22.55
7
BH85 BEML (Empty)
85Te
55.00
22.55
8
BH85 BEML (Load)
85Te
133.00
29.26
C) Parking Brake System
Parking brake system must be conducted on a dry, 15 percent grade surface.
The tests must be conducted with the unit facing both up and down the slope.
Once the unit is in place and the parking brake set, all other holding devices and braking systems must be released and the transmission placed in the neutral position. Any stored energy assist sources (air, vacuum, hydraulic) must be depleted. The unit must remain in this condition without movement for 10
minutes.
Conclusion
Brake is an essential safety feature of the dumper. Utmost care has to be taken in maintaining all type of brake such as service, parking, dumping and emergency for safety of the machine and men. Proper care is to be taken for timely and periodically checking, testing, repairing and complete overhauling of brake system if required
Dragline
General
2)
Safety should be the priority of the operator. In case of any doubt the operator shall consult the super visor.
3)
The operator should understand the operator manual, rules and indicators provided in the equipment. Before starting the machine the operator should sure that it is in safe working order.
4)
The operator should be physically & mentally fit for duty and should not be in intoxicating condition.
5)
Before start of the dragline the operator shall see that there is no body and no light vehicle within the swing zone.
6)
In any Condition the boom and drag bucket shall not be moved over any person.
7)
The operator shall sound horn before start and marching of the dragline.
8)
If there is any bound showing ‘men at work’ and/or any warning board the operator shall not remove it and shall not start the machine.
9)
During marching the boom should be strain fit in the direction of marching and the bucket should be 0.5 meter above the ground.
10)
High tension lines should be minimum 3 meter away from any part of the dragline.
11) The operator shall see that the boulders falling from the bucket dose not hit the power cable.
12) When the bucket gets filled during loading, it should be taken away from the edge.
13) The tub of the machine should be placed on a level & competent ground.
14) When the machine is not in operation the bucket should not be hanged. It should not be kept on the ground.
15) The materials f