Blocked or Broken Valves Procedure

Purpose, Scope and Target Audience

Purpose This chapter contains the global requirements and guidelines to apply when valve is blocked or broken

Scope This chapter applies at all Linde Group sites worldwide.

Target audience The target audience is all staff who are responsible for testing blocked valve acetylene cylinders.

Detecting Blocked or broken Valve:A cylinder with a blocked or broken valve may be detected when:

• There is no pressure reading on the pressure gauge but the cylinder weighs greater than the tare weight.

• The cylinder weighs the same after being on the blow down rack as it did before the blow down rack.

• Confirming blocked or broken valvesIf a cylinder is suspected to have a blocked/broken valve, and there is no reading on the pressure gauge, carry out a “whisper test”. This involves:

• Slowly and briefly opening the cylinder valve.

• If gas escapes, the valve is not blocked/broken, and the cylinder is returned to the blow down rack.

• If no gas escapes, use a nitrogen pressure about 1-2bar and insert the nozzle into the valve outlet.

• Remove the nitrogen nozzle after 5-10 seconds and determine if nitrogen flows back out of the valve.

• If nitrogen flows back out of the valve, the valve is not blocked/broken, and is confirmed empty.

• If nitrogen does not flow back out of the valve, the valve is blocked/broken, and is treated per guidance below.

• Close the cylinder valve.

Be aware that a valve blockage may suddenly become freed and cause acetylene to escape.

General requirementsVenting of acetylene cylinders with blocked or broken valves is performed under the following conditions:

• Under Permit to Work control, approved by the site manager/supervisor

• Using an approved and risk assessed procedure

• On one cylinder at a time, if the procedure involves freely venting acetylene (e.g. gradual valve or fusible plug loosening without a capture system)

• Only by personnel experienced and properly trained in this standard

These precautions are necessary because this operation is hazardous and typically infrequent.

Prepared by Reviewed by Approved by

………………………………... ....….………………….. ..…………………………..Kafi Mahmood Nahin Bashir Hossain Khalilur Rahmana Plant Engineer Maintenance Manager Area Manager