Suppliers to the Jewellery Trade

Technical Information Sheet
Avoid Dangerous Reverse Flow of Gases

1.  Reverse flow can be caused by unequal and unbalanced pressures which can result in mixed gases in hoses, regulators, and gas cylinders.

2.  If this mixture of oxygen and fuel gas is ignited, it can flashback to the source of the mixture through the torch hose, regulator, and to the cylinder and cause serious damage.

3.  Reverse flow can occur when an oxygen cylinder is allowed to empty in use, creating a low or no pressure condition in the oxygen system which allows higher pressure fuel gas to reverse flow back into the oxygen system. The same condition can occur if the fuel gas system reaches a low or no pressure condition due to emptying cylinder.
 

4.  Reverse flow check values on the regulator are designed to stop this reverse flow. If installed, maintained, and tested properly, and used with  proper torch operating procedures, they will give added protection against reverse flow conditions.

5.  Check valves work only if their seats are clean. Soot from torch backfires can keep seats from shutting off tightly and allow a flash back.
 

After work is completed :

• The downstream equipment should be turned off - TURN OFF OXYGEN FIRST, then
• The cylinder valves should be closed - TURN OFF OXYGEN FIRST, then
• The downstream equipment should be safely vented, then
• The regulator pressure adjusting screw should be turned counter-clockwise (to the left) until all spring pressure is relieved, then
• Close all downstream valves, and then
• Secure the equipment.

8.  Always purge torch before each lighting to remove possible mixed gases!

9.  Check valves are designed to stop reverse flow only - not a flashback.