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Work permit system:  Before starting any job in an area, it must ensure that it is safe to work in the environment as well as with the machinery, equipment involved. In order to ensure that no work has to start before ascertaining the safe conditions, the work permit system is being followed.

Work permit system


Work permit authorizes :

  • Specific work to be carry out in restricted or hazardous areas.
  • Serves as an official written record of conditions and requirements as agreed upon between the persons authorizing and receiving the permit.
  • Specifies the conditions and procedures for safe execution of the work and allows the work to be carry out under control conditions.


There are two types of work permit system in KNPC

1) Cold work permit (green):
Shall be obtaine for all general works of maintenance and radiography. Opening of process machinery etc.

2) Hot work (Red):
A hot work/vehicle entry permit is require for the use of a local source of ignition capable of igniting flammable gases, liquids or any other material. Eg, Welding, or entry of petrol/diesel driven vehicles or equipment in the hazardous area, etc.

There are two types of Authorizations:

1) Confined space entry Authorization (yellow):
Confined space is any space large enough for a man to enter and where there could be a presence of dangerous gas or fuel, there is a likelihood of deficiency of oxygen, or access or egress is difficult or restrict. Eg. Vessels, tanks, furnaces, pits, telephone manholes, sewers, excavations deeper than 1.2 meters, floating roof tanks when roof are more than 3m down from the top, etc.

2) Excavation Authorization (White):
Within a restricted area, an Excavation authorization is required for all excavations regardless of depth. For excavations outside restricte areas, excavation authorization is require for excavations deeper than half meter.
Maximum validity of authorization shall not exceed one month (can be renewed two times) and it shall be obtained at least 3 days before the commencement of work.
A cold work permit is required if hand tools are being used for excavation and a hot work permit if powered tools or mechanical equipment are being used.
For Excavations 1200 mm deep or more, a confined space entry permit is required, gas test shall be done as per entry permit requirements.

Gas Concentration limits for the work permit system

Cold work

  • LEL – Less than 10% (up to 20% with air mask)
  • H2S – Less than 10 ppm (should wear SCBA or airline mask at higher concentrations.

Hot Work

  • LEL – Not to exceed 1 %, preferably 0%
  • H2S – Not to exceed 10 ppm

Confined space entry

  • Oxygen – 19.5 to 23.5%
  • LEL – Less than 10% (up to 20% with air mask)
  • H2S – Below 10 ppm (above 10 ppm, entrants should wear Breathing apparatus, above 100 ppm, entry shall not be allowed.
  • Other toxic gases – Reading shall be below TLV for entry without air mask (eg. CO – 25 ppm, Cl2 – 0.5 ppm, SO2 – 2 ppm, NH3 – 25 ppm.) No entry even with BA if LEL is more than 20%, H2S is more than 100 ppm and CO is more than 500 ppm.

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