Reviewed and Approved By:
Catherine L. Fiore, PSFC, Safety Officer
Author: C. Greenspan (Originally, May 7th, 1992)
Date: June 8, 2007 (Original Date May 7, 1992)
This document outlines the hazards involved in handling and using both electric and gas welding equipment at the PSFC. It details the procedures and precautions that should be followed to minimize the risk of personal injury as well as property damage.
This document covers employee safety during the handling and use of welding equipment at the PSFC. It incorporates the safety procedures for welding as outlined by the MIT Environmental Health and Safety (EHS) Office. All welding and cutting operations at MIT must be carried out in accordance with the American Welding Society and the American National Standards Institute (ANSI). This document covers both electric arc welding as well as gas welding and cutting. Any employees using compressed gases for welding should also read and be thoroughly familiar with the Standard Operating Procedures for Handling and Use of Compressed Gases at the PSFC.
Failure to follow the procedures outlined in this document could result in physical and property damage. Misuse of equipment and poor work practices can result in fires, explosions as well as severe skin burns and eye damage.
Many welding operations produce toxic fumes and gases. It is extremely important that the health hazards of the materials worked on are known and that the appropriate precautions are taken. This document covers safety procedures specific to welding and cutting. IT MAY BE NECESSARY TO CONSULT OTHER SOURCES FOR THE NECESSARY SAFETY PRACTICES TO BE FOLLOWED WHEN WORKING WITH POTENTIALLY TOXIC METALS AND METAL ALLOYS.
The supervisor of the person doing the welding or other responsible person shall have employees who handle and use welding equipment designated and trained. The supervisor or responsible person shall ensure that necessary supplies are available to prevent accidents from occurring. The following outlines both general procedures to be followed during all welding and cutting operations as well as specific precautions for electric arc and gas welding:
1. When welding or using a torch, wear lenses for filtering harmful radiation. Filter density requirements should be observed and correct safety glasses obtained through the PSFC Lab Supply or VWR. If unsure what type of glasses or shade of lenses are required, consult the chart in the welding shop near the sink.
2. When welding, a welding helmet should always be worn with cover plates protecting the safety lenses.
3. Head protection (leather hood) must be worn when performing overhead welding or cutting. A hat or other head covering should be worn to protect the head from sparks.
4. Do not wear nylon or other synthetic materials as they can easily melt when contacted by sparks.
5. Wear high cut shoes so that sparks will not fall inside them.
6. Gloves and aprons of leather or other insulating materials should be worn during welding and cutting operations.
7. When welding stainless steel or any material, the vent system should be on and positioned as close to the arc as possible. The switch for the vent is located in front of the welding shop to the left of the breaker panels.
Routine areas for welding must be approved by the MIT EHS Office. Welding should only be performed in designated areas. To perform welding or cutting operations outside of a designated area, a written permit must be obtained from a designated welding supervisor in accordance with MITís Hot Work Permit program.
Welding that must be performed outside of a designated area requires an MIT Hot Work Permit, and in many cases, a fire watch from the Cambridge Fire Department. Contact an authorized hot work supervisor for permits, fire watch details, and smoke detector shutdown coordination.
Hot work should be done at least 50 feet away from combustible materials in all directions. If this is not feasible, fire resistant materials must be used to cover the materials.
Holes in the floors should be plugged to prevent sparks from falling through. A fire watch shall be maintained in the area to watch for unnoticed sparks.
When welding or cutting near a hole in a wall or floor, a fire watch is required on both sides of the wall or floor.
A fire extinguisher shall be maintained in the area and the fire watch shall understand how to use it.
The area should be checked for at least an hour after the welding operation has ceased to verify that no smoldering fires exist. WELDING FIRES CAN OCCUR LONG AFTER WELDING HAS CEASED.
DO NOT WELD ANY CLOSED VESSEL THAT HAS CONTAINED OR IS SUSPECTED TO HAVE CONTAINED FLAMMABLE OR TOXIC MATERIALS UNTIL IT HAS BEEN TESTED, THOROUGHLY CLEANED, VENTED AND PURGED.
Electric Arc Welding:
1. The secondary of the supply transformer and case of any portable welding transformer as well as the frame must be grounded. DO NOT GROUND TO PIPELINES CARRYING FLAMMABLE GASES OR LIQUIDS OR TO CONDUITS CARRYING ELECTRICAL CONDUCTORS.
2. Dry all wet machines. Do not stand in water or on wet ground while welding. Moisture connects your body to the ground and may form the path of least resistance causing a severe shock.
3. Check the whole length of the welding cables for exposed conductors, damaged insulation and slices within 10 feet of holder. Have damaged equipment repaired or replaced. Do not repair with tape.
4. Check electrode holder for loose or exposed connections to reduce shock hazard.
5. Do not loop welding cables around your body.
6. Do not change the polarity switch with the machine is under load. The arching due to the high current can burn the switch contact surfaces or cause serious burns to the welder.
8. Welding machines should be equipped with power disconnect witch in case of emergency.
9. electrode holders should be kept away from electrical power sources and compressed gas cylinders.
10. NEVER strike an arc on a compressed gas cylinder.
11. When no welding is to be performed, all electrodes must be removed from the holders and the machine disconnected from the power source.
Gas Welding and Cutting:
ANYONE INVOLVED IN THE HANDLING AND USE OF GAS WELDING EQUIPMENT SHOULD ALSO READ THE STANDARD OPERATING PROCEDURE FOR THE HANDLING AND USE OF COMPRESSED GASES AT THE PSFC.
1. All cylinders must be stored in a well-ventilated, dry location; at least 20 feet away form combustible materials.
2. Valve protection caps must be in place when the cylinder is not in use.
3. OXYGEN CYLINDERS MUST BE STORED AWAY FROM FLAMMABLE GASES, by at least 20 feet or separated by a non-combustible, 5-foot wall with a fire-resistance rating of at least 1/2 hour.
4. All cylinders must be marked identifying their contents.
5. Cylinders in use must be chained or otherwise secured to prevent falling. Keep cylinders away form any sources of heat or ignition. It this is not possible, heat and fire-resistant shields or covers must be provided.
6. Hoses showing burns or leaks must be immediately replaced.
7. Hoses should be color coded to avoid accidental mixing.
8. Check hose connections for correct threading. Standard hose connections are threaded right hand for oxygen and left hand for acetylene or other fuel gases. THIS HELPS TO PREVENT AN ACCIDENTAL SWITCH OF OXYGEN AND FLAMMABLE FUEL GASES.
9. Do not repair hoses with tape. Test for leaks using soapy solution. If leaks exist, have them replaced or repaired.
10. Use only approved bronze brass fittings. DO NOT use grease or any other readily oxidizable substance on any regulator or torch. Do not handle this equipment with oily rags or gloves.
11. Never face a gage while opening a cylinder. Stand to the side in case of a malfunctioning valve.
12. Do not use oxygen to blow out pipelines or to dust off work or clothing.
13. Acetylene cylinders must be kept and used in an upright position and must never be used at a pressure exceeding 15 psi. Never use acetylene from cylinders without reducing the pressure through a suitable regulation attached to the cylinder valve. Always keep the wrench or key for the acetylene cylinder on the cylinder while in use. Never open the cylinder more than one full turn so that it may be quickly shut off in case of emergency. Make sure that valves are closed when returning empty acetylene cylinders, so as to prevent the evaporation of the acetone solvent.
14. The following describes the proper procedure for lighting and shutting off a gas welding torch. This procedure reduces the possibility of regulator fires when the oxygen cylinder valve is opened again.
a. open acetylene cylinder 3/4/ turn
b. open torch valve 1/4 turn
c. adjust acetylene working pressure with gas regulator screw
d. slowly open oxygen cylinder all the way
e. open oxygen torch valve 1/2 turn
f. adjust oxygen to working pressure with the gas regulator screw
g. close valves on acetylene and oxygen cylinders
h. reopen the acetylene torch valve 1/4/ turn and light gas with friction lighter. NEVER USE MATCHES.
i. open the oxygen valve 1/4/turn. adjust flame.
a. ALWAYS close the acetylene torch valve first, then the oxygen.
b. close the cylinder valves, acetylene first
c. open both torch valves to release the pressure
d. shut off the regulator adjusting handle until you no longer feel any spring tension.
e. close the torch valves.
The supervisor shall supply this procedure
and the SOP for
Compressed Gases to all affected employees and verify that they
In addition, the necessity for knowing the potential health hazards and
precautions for the metals and alloys being welded should be
emphasized. Welders must also complete General Chemical Hygiene
training, Hazardous Waste Management training, Lab Specific Chemical
Hygiene training, and must be familiar with the PSFC chemical hygiene
First Aid Procedure:
Eye and skin
injuries should be
referred to the MIT Medical Department. If the Medical Department
is not open,
then dial 100 for prompt medical aid.
This page maintained by Catherine L. Fiore FIORE@PSFC.MIT.EDU