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This blog contains Safety working Permit system following in industries. Study and Interview Questions included here

Some jobs in chemical plant is dangerous to life and atmosphere and therefore advanced precautions are necessary to avoid accidents.

Work permit system must be prepared with qualified persons and duly signed with all concerned departments. Attachment of Job safety analysis is appreciable.

This blog contains

1. Aspects of Work permit
2. Types of work permit system
3. When work permit exhausted

Interview questions from this blog

1. Which are major work permit categories?
2. Check points of Hot work, Confined space entry?
3. When work permit exhausted and new work permit is required?

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1. Aspects of Work permit

A work permit system is consisting following scopes

1. Work execution department who is seeking a job must be identified in work permit first.
2. Type of work permit
3. Equipment used
4. Identification work permit issuer, work executor, Permit approve person, Area owner.

Work permit issuer may be Engineer, Shift supervisor, Plant in charge, Senior technician, Assistant engineer, etc

Work executor is from service department like Diploma or Engineer in Mechanical, Electrical, Instrument, safety, IT, Third party person.


Permit approving person must be Engineer or equal qualified person with higher experience which holds good knowledge and familiar with all types of risks and scopes of accidents.


Area owner is a person who is operating and working on it. He may be Operator, Technician, Officer, Junior engineer.


5. Permit data must be maintained

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2. Types of work permit system

1. Cold work
2. Cold work at height
3. Hot Work
4. Hot work at height
5. Excavation
6. Electrical
7. Vessel entry

Cold work

The following precautions (though not necessarily exhaustive) should be observed in relation to the performance of Cold Works

1. For work involving the opening-up or de-energizing of equipment, the Lock, Tag and Try Procedure must be followed.

2. If equipment is to be opened up, it should first be depressurized, drained and purged of hazardous material under valve isolation, before positive mechanical isolation can be achieved.

The effectiveness of the valve isolation should be tested and if it is found that a valve is passing, appropriate measures will have to be adopted. 

These may include shutting additional valves or taking further equipment out of commission, the possibility of the presence of wax or ice under a valve should be considered, as subsequent melting would defeat the isolation. 

Where valve isolation is used, the valves should be locked off with chain and padlock or other equally effective device, to ensure that they are not opened inadvertently 

3. If toxic gases could be present, suitable breathing apparatus should be specified. The possibility of the presence of pyrophoric material should be considered before admitting air If necessary, the equipment should be water flushed/filled before opening up and wetted down afterwards.

4 Where hazardous materials such as hydrocarbons and chemicals are involved, mechanical isolation should consist of spading, blanking or disconnecting.

An exception to this requirement would be some cases of minor work when locked off valve would suffice, providing the isolation is proved to be effective by opening drains on the equipment and proving those drains to be clear,

This exception is not made in the interests of expediency, but recognizes that swinging spades or making disconnection can be equally, or more hazardous, than some examples of minor work. 

5. Work should not be attempted on any equipment where the possibility exists of hot material escaping, temperature exceeds its flash point, boiling point or auto ignition temperature. The material should be allowed to cool before draining and extra care exercised when checking isolation integrity.

6. Particular care is required in achieving and proving isolation when equipment operates under a vacuum.

Wherever practicable, a formal maintenance preparation procedure should be written for any equipment where hazards such as hot material or vacuum operation are encountered.

7 Where driven machinery is to be worked on, the prime mover should be positively isolated and any switch gear locked off as per the Lock, Tag and Try Procedure.

8. Appropriate protective equipment must be specified

9. The area around any work site must be appropriately identified and barricaded, if necessary, to prevent other personnel in or passing through the area from being exposed to hazards

Hot Work

Examples of hot work are the use or operation of any of the following:

  1. Welding or flame cutting equipment
  2. Grinder, electric drill or other non-flameproof electrical equipment
  3. Hammering, chipping, drilling (particularly in the presence of flammable/ combustible explosive atmospheres)
  4. Spark ignition engines or non-approved compression ignition engines.
  5. Match, naked flame, cigarette lighter, flame or spark
  6. Hand tools that may create a spark
  7. Non-flameproof electric cables, cords, switches, lights, connectors or fittings 
  8. Any device, which likely to produce a source of ignition or be an ignition source, eg. cell phones, pagers, radios, etc..

Hot Work shall not be carried out in or adjacent to any hazardous area unless a Gas Test has been carried out using an approved explosimeter /toxic gas meter. 

The area or site shall be certified free of flammable vapors and gases and a "Hot Work Permit" issued by an authorized signatory. 

A gas/vapour barrier fence may be required in some circumstances to exclude vapours 
from the work area 

A fully charged fire extinguisher (9kg Minimum dry powder) must always be stationed within easy reach in the work area where Hot Work is involved.

Hot work - Precautions and requirements 

The following safety precautions and requirements, though not necessarily exhaustive, shall be observed before and during the hot work 

1. The equipment to be worked on shall be positively isolated, both mechanically and electrically. Mechanical isolation shall be achieved either by disconnection, or by blanking following the isolation procedure.

2 Blanking is not required for stand-alone utilities supply piping. Utilities supply in this 
instance are process water, potable water, LP/HP De-mineralized water, soft water, 
direct/indirect sea-water, ID cooling water, chilled water, fire water, LP/HP nitrogen, 
steam, plant air, process air, instrument air and steam condensate

Prior to commencement of hot work on the utilities supply line mentioned above, it is of utmost important that the line to be worked on is verified to be cleared and depressurized. This verification can be done by: a) opening a bleed valve (drain valve), b) first break, or c) by doing a cold-cut. The drain valve should be left locked in open position throughout the duration of the hot work to prevent pressure build-up.

3. The equipment shall be freed of liquid and gas by depressurizing, draining, venting 
purging and flushing 

In fined vessels or equipment containing pockets, recesses, double bulkheads, etc. precautions shall be taken to ensure that no material is trapped behind the lining This may require cold drilling and steaming through behind the lining followed by gas testing Where it is not possible to achieve gas free in the equipment or there is a doubt that all potentially hazardous materials have been removed, the space shall be inerted with nitrogen or water filled during hot work.

4. Any combustible material, including paper cartons, aily rugs and grass, located nearby shall be removed Oil spills or deposits around the work site shall be cleaned up. Where it is not practical to remove combustible materials they shall be suitably covered or wetted with water.

5. Drain covers and surface manhole covers within 15 m from the work site shall be properly sealed throughout the work period to prevent emission of flammable vapours

6. If flammable liquid is present in any open drain or ditch which runs within 15m of the work site, it shall be dammed at locations not less than 15m from the work site and pumped out

7. Any potential source of flammable gas or vapor emission, such as sampling point, vent or drain situated within 15m of the work site shall be rendered safe by sealing. 

If there is a potential release of flammable gas or vapor in the vicinity of hot work, it may be necessary to monitor the atmosphere using continuous gas monitors which will alarm on detection.

8. The equipment on which hot work is to be carried out must be certified as being gas free by the authorized gas tester. The equipment cannot be certified as gas free until all sludge, grease, scale, deposits, etc. have been removed, as subsequent work could disturb or heat the remaining materials and give rise to a hazardous condition

9. Gas free condition must also be maintained within 15m from the work site throughout -the hot work period

10 If the hot work could result in the projection of material, the work site must be adequately contained. 

In the case of welding, cutting or grinding, where molten metal and sparks are produced, the work site must be adequately surrounded by fire resistant or flame retarding tarpaulin to contain such sources of ignition. 

Particular attention must be paid to elevated hot work where sparks and molten metal can fall and cause injury to passers-by or ignition to potential sources of flammable or combustible materials underneath The immediate area around and underneath the hot work site must be properly barricaded or roped off with warning signs: Proper ventilation shall be used to ensure the hot work workers do not inhale the welding fumes

11. All hot work sites must be equipped with sufficient portable fire fighting appliances such as fire extinguishers of the appropriate type, fire hose lines charged with water from the nearby fire hydrants.

The end sections of the 2%" hose line shall be 1%" hose connected to the gated "Y" piece with stream/fog shut-off nozzles for easy maneuverability

12. The vicinity of the hot work area where there is a potential of sparks or molten metals falling off the ground shall be wetted with water where practicable.

13. The Performing and Approving Authorities must monitor the progress of hot work on a regular basis to ensure the work group abides by the permit conditions and requirements. 

In the case where hot work, especially heavy hot work, is carried out reasonably close to an operating plant of 'live' system containing hazardous materials, a fire watch from the Performing Authority must be stationed at the work site to closely monitor and supervise the work where practicable.

14. The sitting of mobile equipment such as welding sets and generators must be outside the classified hazardous area and away from the pipe-bridge carrying flammable materials

15. All electrical appliances, connectors and power sockets or extension cords to be used in the classified hazardous areas must be of industrial and flame-proof type.

16, Cigarette or tobacco smoking including the use of lighters or matches at the hot work. site is STRICTLY PROHIBITED even if the work site is covered with a hot work permit

Work at Height

Work carried on 1.8 meter height above standing position. Position have not proper standing space or hazard of falling is including in work at height.

Examples of Working at Height are -
  1. Flat roofs, slopping roofs, fragile roof
  2. Structure erection/ special structure
  3. Working on pipe racks and cable trays, 
  4. Working on flat and sloping tank roofs
  5. Working on tall structures like lighting towers, chimneys, electrostatic precipitators, transmission towers, cooling towers etc.
  6. Insulation of piping at height . 
  7. Confined space work at Height
  8. Loading and Unloading of materials from trucks
  9. Working near Excavations
  10. Working on Bucket Trucks and Man lifts
  11. Painting work inside or outside the building

Excavation Work permit


The following safety precautions, though not necessarily exhaustive, shall be observed where applicable in the course of excavation work to prevent injury and property damage

1. Before an attempt is made to excavate, the Performing Authority must know the exact locations of underground facilities.

2 No excavator or other digging machine shall be allowed to excavate close to underground facilities that must be left in place A proximity limit for machine operations shall be established and the excavation completed by hand digging. When work has to be done over or around electrical cables, special precautions must be stated in the permit If the underground cables, service tiles or any other piping are discovered in the course of excavation, the job must be suspended and the Approving Authority must be notified immediately When mechanical excavator is used, a full time contractor supervisor must be present at the site to guide the operator of the excavator and supervise the excavation. Close proximity digging with any machinery,

SHALL require a person who is knowledgeable of the underground facilities

3 Where a trench to be excavated exceeds 1.5m in depth, adequate piling, shoring and bracing shall be provided against the bank or side to prevent it from collapsing.

Piling, shoring and bracing used in a trench excavation to protect persons against falling or sliding material shall be of adequate strength. Planks used as sheet piling shall be at least 50mm thick. The maximum spacing between horizontal stringers or wales shall be such as to keep the planks within their safe bending stress. Shores and braces shall be of adequate dimensions for stiffness and shall be so placed as to be effective for their intended purposes Each end of each stringer piece shall be separately braced.

Where trenching of more than 4 m in depth is done, such protection shall be constructed in accordance with the design and drawings of a professional engineer, 

4. In every excavation exceeding 1.2m in depth, there shall be provided ladders, stairways or ramps to furnish safe access to and egress from such excavation

5. Excavated material should be placed at least 0.60 m back from the edge of the excavation, unless toe boards or other effective barricades have been installed to prevent fallback The excavated material should be kept away from the drains and access ways

6. Open sides of an excavation where a person may fall in shall be guarded by adequate protective barricades and suitable warning signs shall be put up at conspicuous positions. If the trench is 3m or deeper, barricades made of rigid materials instead of ropes must be used Covering of trench with canvas sheet or the like without such barricades is strictly prohibited.

7 Pick-and-shovel people working in excavations should be kept far enough apart to prevent injury to one another

8. All road-crossing trenches must be covered by steel plates of sufficient strength for vehicles to pass through.

9 Vessel and Confined Space Entry Permit may be required before any person is allowed to enter a trench exceeding 1.5m in depth as the atmosphere in it may not be safe for entry Special attention should be paid to those trenches being dug within process area or any place where there are possible sources of flammable or toxic gas emission. 

Such emission sources may be from the nearby equipment or the pipes underneath the trenches.

Vessel entry permit [Confined space permit]

Under section 36 (2) of factory act- No person allowed or required to enter any confined space. Confined spaces are in factories are Chamber, tank, vat, pit, pipe, flue etc which has possibility of harmful fumes and lack of oxygen.

Until all practicable measures have been taken to remove any fumes which may be present and and to prevent any ingress of fumes and unless a certificate i writing has been give by safety department or other competent person.

Check points :

  1. Formal risk assessment should be done
  2. All electrical energies are isolated in written with signature including date and time
  3. All rotating parts must be locked. Heaters must be isolated. Record should be maintain in written with signature including date and time
  4. All inlets are disconnected, blinded
  5. All drain valves are disconnected and are open.
  6. Temperature should be maintained near room temperature
  7. Flammable and gas content must be checked
  8. Continue air flow inside confined space is provided fresh breathing air.
  9. Manhole is bonded with heavy rope or chain which are not breakable.
  10. Outside standby person is required with this dedicated job.
  11. No gas cylinder is allowed to bring inside except SCBA Set
  12. Written rescue plant must available and placed near to work place
  13. Oxygen is checked in each 2 hours.
  14. Good lighting must provided (24 volts).
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3. When work permit exhausted

1. After continuous work of 6 days work permit will not valid and re issued
2. After break of work work permit ends.
3. After work completed notification same work permit is not valid. Re issue will be initiated.
4. In the case of work permit type change, Found new way to complete with different method work permit not valid new permit must be issued.

Work permit examples

work-permit-example

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Thanks for reading - Safety work permit system | Safety blog
Naitik Patel
Industrial Guide

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