At start-up, purge your CNG fueling system of air

Posted by cngcenter on May 16, 2013 in Tips

Natural gas is highly explosive when combined with oxygen and an ignition source. In order to operate your NGV station safely, you should remove all the air from the system especially at start-up.

We suggest using an inert gas such as nitrogen. Here are some simple steps to follow; remember these are a simple guide and may or may not apply to your specific module.

1. Open the manual drain valve on the vent recovery tank. Turn auto condensate drain manual “dump valves” to the dump position.
2. Open isolation valves to allow inlet pressure to the inlet solenoid valves.
3. Turn the motor starter(s) “ON” and begin normal compressor operation.
4. Open the pulsation tank drain valve slightly to allow gas to flow out while maintaining 1-2 psig on the compressor inlet. After three minutes, close the pulsation tank drain valve.
5. Open each inlet filter bowl manual drain valve slightly to vent gas from the inlet filter bowl. Drain valves for one minute, then close each valve.
6. Vent the compressor frame by removing the snifter valve cap and depressing the valve slightly. While maintaining at least one (1) psig on the compressor inlet, vent the frame until oil mist appears.
7. Continue to run the system while dumping through out the recovery tank manual drain valve for five minutes. Close the manual drain valve.
8. Turn auto condensate drain manual dump valves to the normal position.
9. Vent the compressor frame a second time by depressing the snifter valve slightly while maintaining at least one (1) psig on the compressor inlet. Vent the frame until oil mist appears. Replace the valve cap.
10. Vent the recovery tank through the manual drain valve located on the tank for three minutes.
11. Vent the final discharge line through the user supplied purge valve.
12. Continue to purge gas through all remaining pressurized components downstream of the compressor.
13. If using nitrogen to purge the system, re-purge the entire system with natural gas.
14. Upon completion, recheck position of each manual valve, securing as necessary. After waiting for the areas to be free of gas fumes which might lead to false readings, proceed with a leak check on all connections and valve seats.
15. Remember, air can be reintroduced into the system if the unit is allowed to pull a vacuum anywhere in the system. If this happens, re-purge for your own safety.