The hydrostatic relief valve is used on which line to release excessive pressure caused by trapped liquid natural gas?

The hydrostatic relief valve is used on which line to release excessive pressure caused by trapped liquid natural gas?

• A. Natural gas liquid line
• B. Natural gas line
• C. Water line
• D. Propane line

Answer: (A)

The key idea is that a hydrostatic relief valve responds to pressure created by a column of liquid. In LNG systems, trapped liquid natural gas in a line can develop high pressure from the weight of the liquid (the hydrostatic head) or from thermal expansion. Placing the relief valve on the natural gas liquid line allows it to vent enough vapor to prevent overpressure and potential rupture. If it were placed on a gas-only line, or on a water or propane line, the same hydrostatic pressure situation wouldn’t exist or would be addressed by different safety devices, so the natural gas liquid line is the correct location for this valve.

The key idea is that a hydrostatic relief valve responds to pressure created by a column of liquid. In LNG systems, trapped liquid natural gas in a line can develop high pressure from the weight of the liquid (the hydrostatic head) or from thermal expansion. Placing the relief valve on the natural gas liquid line allows it to vent enough vapor to prevent overpressure and potential rupture. If it were placed on a gas-only line, or on a water or propane line, the same hydrostatic pressure situation wouldn’t exist or would be addressed by different safety devices, so the natural gas liquid line is the correct location for this valve.