Safety Precautions while Doing Hot Work
Hot Work Accidents Accidents as a result of hot work can occur because of several reasons. One of the most common ones are when hot work is being carried out in enclosed space with flammable gases, when the adjacent tank has flammable material, as a result of flammable gas pockets etc. It is also seen that seafarers often fail to follow the basic hot work procedures while carrying out such procedures, leading to unfortunate, fatal accidents.
Following procedure to be followed for carrying out hot work maintenance on ships: 1. Refer and follow "Hot Work Precautions Matrix" before starting the job; 2. A work planning meeting to be held and a formal or informal risk assessment to be carried out of the work place; 3. A responsible officer, who is not directly involved in the hot work, must be designated to ensure that the plan is followed; 4. The atmosphere of the hot work area should be tested and found to be less than 1% LEL; 5. Fire fighting equipment must be arranged and kept ready for immediate use; 6. Fire detectors of the work place must be checked for proper working; 7. Measures should be taken to prevent scattering sparks, such as spark shelters; 8. Confirm that no other work such as repairing pipelines, that may cause leak of combustible gas or oil, is being done in the same compartment; 9. Arrangements for placing required watchmen for monitoring hot work area and adjacent areas should be made; 10. Provision must be made for sufficient ventilation and lighting; 11. Evacuation routes/passages must be properly designated/secured; 12. The condition of tools and equipment must be checked and found satisfactory; 13. Personnel involved in work must be provided with appropriate personal protective equipment and danger indications, safety ropes etc. installed at work site as necessary; 14. Areas where fire is directly applied must be clearly marked; 15. All crew engaged in the hot work should be adequately trained and clearly instructed in precautions to be observed when carrying out hot work; 16. Measures must be taken to prevent fire from coming in contact with gas, residual oil, sludge and other dangerous and combustible materials; 17. Check there is no dangerous and combustible materials on the other side of the bulkhead, deck head or division on which hot work is to be carried out; 18. The section to be worked on should be disconnected or disassembled from related pipelines and valves by cold work and the open ended section must be sealed off; 19. The safety in the pipe must be confirmed where applicable; 20. The safety of enclosed compartments must be confirmed in accordance with procedures for entry into enclosed spaces where applicable; 21. All crew engaged in work within enclosed space must be provided with portable lighting apparatus; and 22. Gas detection in spaces where there is danger of combustible gas emissions (air pipe tops, areas near manholes, other openings and the like) and in vicinity of the hot work area must be carried out prior work and should continue periodically during work.
Some most safety precautions to follow while doing gas welding/hot work are:
Secure Gas Cylinders in Vertical Position: Compressed gas cylinders must be handled with utmost care and always be secured in vertical position even if they are full or empty. Full and empty cylinders to be segregated and marked clearly.
Store in Right Spaces: Never store oxygen and acetylene cylinder together in one space whenever possible. Keep them separately in well ventilated spaces. Ensure when not in use, their caps should always be on them.
Keep Grease and Oil Away: Control valves and fittings should be kept free of oil and grease. Never operate cylinder valves and parts with oily and greasy hands.
Ensure Flame Arrester Are Properly Fitted: Ensure non-return valves and flame arresters are fitted in the acetylene and oxygen cylinder lines. One flame arresters is normally fitted in the low pressure side of the regulator near cylinder and other near the torch.
Keep Pressure of Oxygen Higher: When performing gas welding, ensure the pressure of oxygen is always higher than the acetylene to avoid acetylene going back to the oxygen line.
Handle Acetylene With Care: Acetylene should not be used for welding at a pressure exceeding 1 bar of atmosphere gauge as it is liable to explode, even in the absence of air, when under excessive pressure.
Rectify Cause of Backfire: In case of back fire, the first priority should be to close the oxygen valve and then immediately close the acetylene valve. No operation is to be performed until the cause of backfire is rectified.
Handle Flashback Carefully: In case of flashback or explosion of the gas pipes, first action must be to isolate the cylinder valves for both the cylinders. Further action to be taken as per ship’s fire drill procedures.
Ensure Proper Connections: The connections between the hose and blowpipe and between hoses should be securely fixed with fittings to comply with Regulatory Standard.
Keep a Steady Watch: A regular watch to be kept on the temperature of acetylene cylinder. If the temperature is elevating, it is to be considered same as flashback or explosion situation for taking action.
Prevent Interchange of Hoses: Manifold hose connections including inlet and outlet connections should be such that the hose cannot be interchanged between fuel gases and oxygen manifolds and headers.
Replace Old and Faulty Hoses: Any hose in which flashback has occurred must be replaced with new one.
Handle Hoses Properly: While performing the job, the hoses should be laid properly and kept out of any moving machinery, sharp corners, high temperature areas etc. Ensure they are not dangled, knitted or tipped over.
Use Only Soap Water for Leakages: Only soap water to be used for detection of leak from hose or regulator arrangement.
Never Use Sealing Tape: Never use sealing tape of metal joining material to prevent leak between metal to metal gas tight joints. With an oxygen cylinder this could result in initiation of a metal- oxygen fire.
Never Over Tight Connections: Never try to over tight any nut of regulator connection or cylinder valve spindle to stop the leak. This can lead to damage.
Take Proper Steps for Maintenance: Only special tools should be used to clean any clogging in the blow pipe. Before performing any maintenance, complete system to be isolated. Never attempt repairs on pressurized oxy-acetylene equipment nor carry out any unauthorized modification on hot work equipment.
Use Safe Igniters Only: Blowpipe should only be ignited with friction igniter or other stable flame generator. Avoid using lighter as sudden flame, else blowpipe can hit the lighter body and explode.
Never Use Oxygen: Oxygen should never be used for ventilation, cooling purpose or for blowing dust off the surface or clothes.
Discard Hoses That Had Flashback: Any length of hose in which a flashback has occurred should be discarded immediately. Last but not the least, make sure before carrying out any kind of hot work, the hot work checklist and risk assessment forms have been duly filled. Also, do not forget to follow all safety procedures while carrying out such jobs in enclosed spaces.