When performing a hydrostatic test, when should the gag be installed on the safety valve?

In the context of performing a hydrostatic test, installing the gag on the safety valve when the pressure reaches at least 80% of the set pressure is crucial for ensuring the safety and integrity of the test. The gag is used to prevent the safety valve from opening during the test, which could lead to depressurization and potential hazards.

By waiting until the pressure reaches at least 80% of the set pressure before installing the gag, the operator ensures that the test pressure is sufficiently close to the valve’s operational limit. This significantly reduces the risk of the safety valve inadvertently opening and disrupting the testing procedure, while still maintaining a safe environment for the test itself. Engaging the gag before this pressure threshold might not provide a full assessment of the system's integrity at operational pressures, as the valve’s function would not be accurately reflected.

This practice aligns with safety protocols and industry standards aimed at protecting both personnel and equipment during hydrostatic testing, making it the recommended approach in such scenarios.