Practice Test Geeks(API 510) Certified Pressure Vessel Inspector Practice Test
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Pressure Relief Devices Flashcards

7 cards from real API 510 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. When multiple pressure relief valves are installed to protect a single pressure vessel, what is the maximum set pressure allowed for the additional (supplemental) valves per ASME Code UG-134?

    Answer: 105% of MAWP

    ASME Code UG-134 allows supplemental PRVs (additional valves beyond the first) to be set at up to 105% of the vessel MAWP.

  2. In pressure relief valve terminology, 'back pressure' is defined as:

    Answer: The pressure existing at the outlet (discharge side) of the pressure relief device

    Back pressure is the pressure at the outlet of a pressure relief device resulting from conditions in the discharge system such as header pressure or elevation.

  3. Which type of pressure relief valve is MOST sensitive to variable or high superimposed back pressure, which can raise its effective set pressure?

    Answer: Conventional spring-loaded pressure relief valve

    In a conventional spring-loaded PRV, back pressure acts directly against the spring force on the disk, effectively increasing the set pressure by the amount of back pressure.

  4. According to API 520, what is the maximum allowable non-recoverable inlet pressure drop to a pressure relief valve to prevent valve chatter during a relief event?

    Answer: 3% of set pressure

    API 520 recommends that the non-recoverable inlet pressure drop not exceed 3% of the set pressure to prevent chatter, which causes rapid cyclic opening and closing that can damage the valve.

  5. What is 'Cold Differential Test Pressure' (CDTP) as applied to pressure relief valve bench testing?

    Answer: The adjusted set pressure used during bench testing to account for operating temperature and back pressure effects

    CDTP is the adjusted set pressure applied during bench testing at ambient conditions to compensate for the effect of operating temperature on spring characteristics and for superimposed back pressure.

  6. Why is a pilot-operated pressure relief valve (POPRV) preferred over a conventional spring-loaded PRV in applications with high or variable back pressure?

    Answer: The POPRV set pressure is determined by the pilot valve sensing inlet pressure, making it independent of outlet back pressure

    In a POPRV, the pilot valve senses only inlet pressure to control the main valve, so back pressure at the outlet does not affect the set pressure, unlike a conventional spring-loaded valve.

  7. After a pressure relief valve is removed, repaired, and bench tested, what must occur before it is returned to service on a pressure vessel per API 510 requirements?

    Answer: Its set pressure and operating characteristics must be verified by testing and documented

    API 510 requires that after any repair or maintenance, the PRV must be tested to verify its set pressure and functional characteristics are correct, and the results must be documented before the valve is returned to service.