API576

Question 1

Types of RV? (5)

Answer 1

safety valve
relief valve
conventional safety-relief valve
balanced safety-relief valve
pilot-operated pressure-relief valve.

Question 2

safety valve

Answer 2

1. normally used with compressible fluids

2. Rapid Open or pop action

Question 3

The term pressure-relief valve is generic in nature,can be classified as a (3)

Answer 3

safety valve, relief valve, or a safety relief valvE

Question 4

relief valve is a pressure-relief valve actuated by the difference between

Answer 4

static pressure upstream of the valve and superimposed backpressure downstream

Question 5

Relief Valve

Answer 5

1. opens in proportion to the pressure increase over the opening pressure (not pop action)
2. Relief valves usually reach full lift at either 10 % or 25 % overpressure
3. have closed bonnets to prevent the release of corrosive, toxic, flammable,
   or expensive fluids.
4. used for incompressible fluids (liquids)
5. should not be used:
   in steam, air, gas, or other vapor services;
   installations that impose any backpressure
   as pressure control or bypass valves.

Question 6

Safety Relief Valve

Answer 6

1. May be used as either a safety or relief valve
2. fully open at 10 % overpressure when in gas or vapor service.
3. in liquid service, full lift will be achieved at approximately 10 % or 25 %
   overpressure
4. Two types of Safety Relief Valves
   Conventional Safety-relief Valve
   Balanced Safety-relief Valve

Question 7

cold differential test pressure

Answer 7

pressure at which a pressure-relief valve is adjusted to open on the test stand. The cold differential test pressure includes corrections for the service conditions of superimposed backpressure or temperature or both.

Question 8

conventional valve can utilize a closed spring bonnet that will allow any backpressure to be contained within all areas of the valve downstream of the seat. This backpressure can affect the set pressure, stability, and available capacity that can be provided.

Question 9

Conventional Safety Relief Valve par 4.4

Answer 9

1. directly affected by changes in the backpressure
   2.has a bonnet that encloses the spring and forms a pressure-tight cavity.
2. Used in flammable, hot, or toxic material
   effect of temperature and backpressure on the set pressure

Question 10

Balanced Safety-relief Valve par 4.7

Answer 10

1. incorporates a bellows or other means for minimizing the effect of backpressure on the operational characteristics of the valve
2. Used for;
   flammable, hot, or toxic material, where high backpressures are present in gas, vapor, steam, air, or liquid services; in corrosive service
   when the discharge from the valves is piped to remote 3. The bonnet of a balanced pressure-relief valve shall be vented to the atmosphere at all times for the bellows to perform properly.

Question 11

blowdown

The difference between the

Answer 11

set pressure and the closing pressure of a pressure-relief valve,

Question 12

Pilot Operated Valves used for

Answer 12

Used for;
1. where a large relief area and/or high set pressures
2. low differential exists between the normal vessel operating pressure and the set pressure
3. large low-pressure storage tanks
4. very short blowdown is required
5. where backpressure is very high and balance design is required, since pilot-operated
valves with the pilots either vented to the atmosphere or internally balanced are
6. inherently balanced by design;
sensing of pressure at one location and relief of fluid at another location;

Question 13

Pilot Operated Valves NOT used for (3)

Answer 13

Not used;
In dirty or fouling service
Liquid service 
with vapors that will polymerize
High temperature service (due to o-rings in pilot valve

Question 14

There are three major rupture disk types:

Answer 14

forward acting, reverse acting, and graphite.

Question 15

Forward-acting (3) types

Answer 15

convention / scored / composite

Question 16

Forward-acting Conventional Rupture Disk (2)

Answer 16

1. formed (domed), solid metal disk designed to burst at a rated pressure applied to the concave side
2. These disks have a random opening pattern and are considered fragmenting designs that are NOT suitable for installation upstream of a pressure-relief valve.

Question 17

Forward-acting Scored Rupture Disks

Answer 17

1 . burst along score lines at a rated pressure applied to the concave side
2. are considered fragmenting designs that are suitable for installation upstream of a pressure-relief valve.

Question 18

Forward-acting Composite Rupture Disks

Answer 18

1 . composite rupture disk is a flat or domed multi-piece construction disk.
2. SOME are considered fragmenting designs that are suitable for installation upstream of a pressure-relief valve.

Question 19

Reverse-acting Knife Blade Rupture Disks

Answer 19

Knife blades installed in holders should be constructed of corrosion-resistant material and should be in- spected periodically to ensure sufficient sharpness to open the disk. Dull or damaged knife blades will likely prevent proper opening of the disk. See Figure 11.

Question 20

Reverse-acting Scored Rupture Disks

Answer 20

generally are considered fragmenting designs that are suitable for installation upstream of a pressure-relief valve.

Question 21

Graphite Rupture Disks

2

Answer 21

Graphite, shear-loaded rupture disks are flat and are designed to open by bending and/or shearing of the membrane

Graphite rupture disks WILL fragment upon rupture.

Question 22

Causes of improper performance (6)

Answer 22

1. Corrosion is a basic cause of many of the difficulties encountered with pressure-relief devices a rupture disk device installed on the inlet or outlet of a pressure-relief valve can provide added corrosion protection
2. lengthy piping to the valve inlet. These can cause a valve to chatter.
3. Careless handling during maintenance
   piping strains resulting
4. Improper blowdown ring settings. This can cause a valve to chatter.
5. Severe oversizing of the pressure-relief valve

Question 23

Failed Springs

Two forms of failure;

Answer 23

1.Weakened by corrosion

Failed springs are almost always due to corrosion
Weakened spring causes a reduction in set pressure and the possibility of premature opening.

2. Spring breaks

Broken spring causes uncontrolled valve opening.

Question 24

Pressure-relief valves that do not pop at inlet pressures of ____of CDTP should be considered as stuck shut

Answer 24

150 %

Question 25

The primary reasons for applying rupture disks upstream of pressure-relief valves include the following. (4)

Answer 25

a) Prevent plugging of pressure-relief valve— b) Prevent corrosion of pressure-relief valve— c) Avoid cost of high alloy pressure-relief valve—High alloys or exotic alloys for rupture disk construction cost much less than a corresponding relief valve with the same alloy trim. d) Prevent leakage through pressure-relief valve—

Question 26

PRD set pressure tolerances allowed according to ASME for up to 70 PSI AND >70PSI

Answer 26

The set pressure tolerances, plus or minus, of pressure relief valves shall not exceed 2 psi (15 kPa) for pressures up to and including 70 psi (500 kPa) and 3% for pressures above 70 psi (500 kPa).

Question 27

the rupture disk shall be the (2) ________as the pressure-relief valve inlet

Answer 27

same nominal pipe size / Or larger.

Question 28

accumulation

Answer 28

The pressure increase over the maximum allowable working pressure (MAWP) of the vessel or piping system,

Question 29

superimposed backpressure

Answer 29

The static pressure that exists at the outlet of a pressure-relief device at the time the device is required to operate. (NOT YET OPEN)

Question 30

backpressure

Answer 30

The pressure that exists at the outlet of a pressure-relief device as a result of the pressure in the discharge system. Backpressure is the sum of the superimposed and built-up backpressures.

Question 31

built-up backpressure

Answer 31

The increase in pressure at the outlet of a pressure-relief device that develops as a result of flow after the pressure-relief device opens. (OPENS)

Question 32

blowdown

Answer 32

The difference between the set pressure and the closing pressure of a pressure-relief valve, expressed as a percentage of the set pressure or in pressure units.

Question 33

simmer

Answer 33

The audible or visible escape of compressible fluid between the seat and disc, which may occur at an inlet static pressure below the set pressure prior to opening.

Question 34

type of valve that has a huddling chamber?

Answer 34

safety

Question 35

Reverse-acting Scored Rupture Disk (2)

Answer 35

pressure applied on the convex side, thicker disk materials may be used, thereby lessening the effects of corrosion, eliminating the need for vacuum support, and providing LONGER SERVICE LIFE AND highest operating pressure

Question 36

To prevent leakage of the loading fluid, an optical precision on the order of ____ light beads/bands according to manufacturer’s specifications should be maintained in the flatness of seating surfaces on metal-seated pressure-relief valves

Answer 36

three

Question 37

what can cause chatter? (2)

Answer 37

1. long piping between vessel and RV 2. improper blowdown ring setting 3. oversizing the RV

Question 38

oversizing the RV

Answer 38

cause the valve to cycle (open/close repeatedly)

Question 39

To ensure that the valve is opening, produce a ____ at the set pressure

Answer 39

distinct pop

Question 40

as-received pop testing should be conducted prior to cleaning in order to yield accurate that will help establish

Answer 40

appropriate inspection and servicing interval.

Question 41

Once the valve is set to pop at its CDTP, it should be checked for leakage. On the test block, it can be tested for seat tightness by increasing the pressure on the valve up to the manufacturer’s specified simmer pressure (oftentimes this is ________ of the CDTP)

Answer 41

90 %

Question 42

There are three applications for Rupture Disk Devices:

Answer 42

4. 5.3.2 Single Relieving Device a) When complete discharge of the process contents can be tolerated when the disk ruptures. b) When a fast opening response is required. 4. 5.3.3 Supplemental Relieving Device a) To provide larger relief area for remote likelihood overpressure scenarios.