What specific feature must pressure relief valves for CNG service have?

Pressure relief valves (PRVs) for CNG service are critical safety components designed to protect pressurized systems from overpressure conditions. The correct requirement for these valves is that they must include means to prevent unauthorized tampering. This feature is vital as it ensures that the pressure relief mechanism remains functional and reliable, ultimately preventing dangerous situations that could arise from overpressure and potential explosions or leaks.

The ability to prevent unauthorized tampering helps maintain the integrity of the pressure relief system. When tampering is possible, there is a risk that individuals might adjust or disable the valve inappropriately, leading to unsafe operating conditions. Therefore, having tamper-proof features is essential for maintaining safety standards in CNG facilities.

In contrast, other features such as being adjustable without a seal, being fitted with lifting devices, or being removable without restrictions do not generally apply as essential safety requirements for pressure relief valves specifically designed for CNG. Adjustability can lead to unauthorized changes that compromise safety, and any unrestricted removal could expose the system to risks, undermining the purpose of the pressure relief device.