Tips for Valves
Best Practices: How to get the Most out of Valves
High Pressure Gas Testing Specifications
For natural gas pipelines, high pressure nitrogen gas testing would follow the hydro test. While pressure testing the line with nitrogen, the valve should be operated first in the half open position to pressurize the body cavity and then returned to the full open position. The body vent or drain valve should then be opened and closed to drain the water from the body cavity. When all water has been removed, the valve needs to be brought back to the fully open position and lubricated further.
With the pipeline under normal operating pressure, the valve technician can now inspect the valve for seat leakage. Then, verification of each valve being tightly sealed in both full open and full closed positions can be done. Leakage, if any, is visually monitored by opening the body vent fitting with the main valve in the fully open or in fully closed position only. In the event that minor leakage persists, the valve should be topped up with more lubricant or sealant and the valve stops need to be adjusted in an attempt to achieve a perfect seal.
When the sealing is achieved, the actuator stops and should be locked in to position. In the event that a seal cannot be maintained, the valve manufacturer’s representative should be consulted for recommendations. In the event that leakage is very minor, a heavier sealant may be injected upon mutual consent of the operator, contractor and valve manufacturer.