Q1. The amount by which the pressure in a vessel rises above MAWP when the pressure-relieving device is fully open and discharging is known as?
(a) Back pressure build-up
(b) Accumulation
(c) CDTP
(d) Blowdown
Q2. Generally speaking, which of the following is true for a pressure vessel (according to API 576)?
(a) MAWP is always the same as design pressure
(b) MAWP is normally greater than design pressure
(c) MAWP is normally lower than design pressure
(d) MAWP = design pressure – back pressure
Q3. What is back pressure?
(a) Pressure in the PRV inlet line
(b) Pressure in the PRV discharge line before the PRV lifts
(c) Pressure in the PRV discharge line after the PRV lifts
(d) The sum of (b) and (c) above
Q4. Cold differential test pressure (CDTP) is:
(a) The pressure at which a PRV is set to lift on the test stand
(b) The pressure at which a PRV is set to lift under service (hot) conditions
(c) ‘Set pressure’ + 10 %
(d) ‘Set pressure’ + back pressure
Q5. In API 576, the term ‘PRV’ refers to:
(a) Only valves that exhibit a defined ‘pop’ action
(b) Only valves that do not exhibit a defined ‘pop’ action
(c) Only those valves defined as ‘safety’ relief valves (API 576 section 4.4)
(d) All of the above. PRV is a generic term &
Q6 Can safety valves be used in corrosive service without being isolated from the process fluid by a rupture disc on the inlet side?
(a) No, it is not recommended
(b) Yes, as long as the seat is corrosion-resistant
(c) Yes, as long as it has an enclosed bonnet
(d) Yes, as long as the fluid is compressible
Q7. What is the fundamental difference between the opening characteristic of a relief valve compared to that of a safety valve?
(a) A relief valve has a lower measured lift
(b) A relief valve opens without a ‘pop’, in proportion to the pressure increase over the opening pressure
(c) A relief valve contains a huddling chamber, giving a proportional opening
(d) A relief valve should not be used on liquids
Q8. Which of the following damage mechanisms (DMs) would be unlikely to affect conventional rupture discs, causing premature failure?
(a) Fatigue
(b) Stress corrosion cracking
(c) Creep stress failure
(d) Brittle fracture
Q9. Failed PRV springs are almost always caused by:
(a) Plastic deformation (‘set’) of the spring due to continual use
(b) Fatigue
(c) Brittle fracture
(d) Surface corrosion and/or stress corrosion cracking
Q10. Which of the following is unlikely to be a cause of sticking of a valve disc in its guide?
(a) Machining of components outside their tolerance limits
(b) Use on process fluids such as coke or catalysts
(c) Use of a balanced (bellows-type) PRV
(d) Galling of mating components
Q11. Rough handling of a PRV can result in problems with seat leakage. The standard used to specify PRV leakage is?
(a) API 576
(b) API 596
(c) API 527
(d) API 572
Q12. In order to minimize the chances of damage to PRV seating surfaces, PRVs should be shipped:
(a) In an upright position
(b) Lying on their side (firmly secured to a pallet)
(c) With the spring fully compressed
(d) With the spring fully extended
Q13. Before removing PRVs from the plant, it is an important safety requirement to check that:
(a) The spring is released
(b) The connecting pipework and any block valves are adequately supported
(c) They are ‘pre-pop’ tested first
(d) The discharge connection to atmosphere is blanked off
Q14. During its first as-received pop test, a PRV opens at 120 % CDTP. It is tested a second time and opens at 105 % CDTP (a pressure considered acceptable under the applicable code).
Which pop pressure result should be used as the basis of
determining the inspection interval for this PRV?
(a) 105 % CDTP
(b) 105 % CDTP ± 10%
(c) 120 % CDTP
(d) CDTP
Q15. When is it acceptable for a user to waive the ‘as-received’ pop test on a very dirty PRV and still be in compliance with API 576?
(a) Never
(b) If the PRV is the balanced (bellows) type
(c) If the PRV has not been in HF service
(d) If the inspection interval is immediately reduced, and then assessed again at the next inspection
