Valves

Question 1

If no specific orientation is given for the valve stem, how should the stem in a gate valve be oriented?

Answer 1

Preferably with stem set in the vertical up position.

Question 2

What special feature might be required for a gate valve installed in a vertical line?

Answer 2

A drain tapped into the valve to provide drainage above the disc.

Question 3

What is the last thing the installer should do to complete the installation of a valve in a line?

Answer 3

Operate the valve through a complete cycle after it’s installed.

Question 4

What is the function of the valve stem when opening a globe valve that has pressure under the disc?

Answer 4

Controls the rate that the disc moves up from the seat.

Question 5

What key factor does the valve manufacturer need to know to ensure that a swing check valve will operate in the full open position?

Answer 5

The velocity of the fluid in the line.

Question 6

Why would a tilting disk check valve be chosen over the same size swing check valve?

Answer 6

A tilting disk check valve will operate at very low velocities.

Question 7

What flow condition can be reduced or eliminated with the use of a spring loaded check valve?

Answer 7

Water Hammer

Question 8

A valve is found with leakage through the bonnet connection. When the valve bonnet is removed, you find the gasket damaged. What is the recommended repair?

Answer 8

Replace the gasket.

Question 9

A valve failing frequently in service. The seats are damaged and have to be changed frequently. What is the probable cause and suggested solution to this problem?

Answer 9

The seat material is too soft, replace with harder seat.

Question 10

What is required in most plants before any component can be removed from a system or piece of equipment?

Answer 10

Safe Work Permit

Question 11

The most common service done on a gate or globe valve is to replace the stuffing boxes. Why would a safe work permit have to be obtained to repack a valve stuffing box?

Answer 11

The packing is the seal between the system product and outside environment.

Question 12

What is the correct packing size to use if the valve stem measures 19mm(3/4”) OD and the stuffing box measures 32mm(1 1/4”)?

Answer 12

32-19=13
13/32=6.5mm(1/4”) square

Question 13

What should be done with coil or spiral packing before inserting it into the stuffing box?

Answer 13

Cut the packing into separate rings.

Question 14

If butt-cut rings are cut on a flat surface, what should be done to ensure that the end cut of the rings can be reproduced accurately?

Answer 14

Be certain that the side of the ring, and not the OD or ID surface, is laid on the rings to be cut.

Question 15

What group is still considered to be at the forefront of valve standards activities?

Answer 15

The Manufacturers Standardization Society of the Valve & Fitting Industry (MSS)

Question 16

Why would a chemical or refinery valve specifier reference an API 6D valve standard?

Answer 16

6D’s zero allowable leakage on closure tests.

Question 17

Which code or standard is most often referenced for chemical or refinery globe and check valve specifications?

Answer 17

ANSI B31.3

Question 18

What are four factors that should be considered when choosing the correct valve for an installation?

Answer 18

Pressure
Temperature
Flow Rate
Type of Fluid

Question 19

What feature of Y pattern and angle pattern globe valves allows them to be used in blowoff or blowdown service where mud or sludge has to be removed from a vessel?

Answer 19

Valve seats are self scouring.

Question 20

What is the type of valve most widely used in the industry? Why?

Answer 20

Ball Vale
Offers higher rate of flow, quick and easy operation, simple design, and requires less maintenance.

Question 21

What are check valves designed to do?

Answer 21

Prevent back flow.

Question 22

What are two main types of check valves?

Answer 22

Lift Check
Swing Check

Question 23

Why would you use a globe valve instead of a gate valve?

Answer 23

Throttling flow.

Question 24

What is the recommended position that a valve should be installed?

Answer 24

With stem in the upright position.

Question 25

What is meant by equivalent length?

Answer 25

The loss of pressure in the line caused by the valve or fitting in relationship to a length of pipe.

Question 26

What is the abbreviation NRS?

Answer 26

Non-Rising Stem

Question 27

What is the abbreviation AWWA?

Answer 27

American Water Works Association

Question 28

What is the abbreviation RS?

Answer 28

Rising Stem

Question 29

What is the abbreviation WOG?

Answer 29

Water, Oil, or Gas

Question 30

What is the abbreviation S?

Answer 30

Steam

Question 31

What is the abbreviation 125WOG?

Answer 31

125 psi maximum operating pressure Water, Oil, or Gas

Question 32

What is the abbreviation 125S?

Answer 32

125 psi maximum operating pressure Steam

Question 33

What type of valve is most suited for throttling?

Answer 33

Globe Valve

Question 34

What is the function of a ball valve and under what service conditions would it be used?

Answer 34

To start and stop the flow of fluids, used in almost any application.

Question 35

What types of valves would be best for laminar flow, non-throttled?

Answer 35

Ball or gate valve.

Question 36

What types of valves would be best for very close throttling?

Answer 36

Needle Valve

Question 37

What types of valves would be best for restricted head room, non-throttling?

Answer 37

Ball or non-rising stem gate valve.

Question 38

What types of valves would be best for change direction and throttle?

Answer 38

Angle Globe Valve

Question 39

What is the main advantage of an NRS valve?

Answer 39

Requires less headroom to operate.

Question 40

What is the main advantage of outside screw and yolk?

Answer 40

Threads do not come in contact with fluids.

Question 41

What is the main advantage of non-rising stem?

Answer 41

Headroom.

Question 42

What is the main advantage of diaphragm valve?

Answer 42

No packing, less maintenance.

Question 43

What is the main advantage of lantern ring?

Answer 43

Better lubrication.

Question 44

What is the main advantage of composition discs?

Answer 44

Easily replaced to accommodate other applications.

Question 45

What is the main advantage of Y pattern valves?

Answer 45

Pressure loss kept to a minimum.

Question 46

What is the main advantage of plug disc valves?

Answer 46

Minute throttling applications.

Question 47

What is the main advantage of rising stem valves?

Answer 47

Easy to tell if the valve is open or closed.

Question 48

What is the main advantage of needle valves?

Answer 48

Very fine throttling at high pressures.

Question 49

What is the main advantage of ball valves?

Answer 49

Quick response, low maintenance.

Question 50

What are valves that require only a 90• turn from fully open to fully closed classified as?

Answer 50

1/4 turn

Question 51

What is the S or SWP rating on a valve related to?

Answer 51

Maximum pressure allowed at saturation steam temperature.

Question 52

What physical damage is most likely to occur to a plug or seat of a non-lubricated metal to metal plug valve used under high pressure?

Answer 52

Galling.

Question 53

What condition in a system would most likely require the use of a tilting disc check valve?

Answer 53

Low velocity flow.

Question 54

What is a OS&Y valve?

Answer 54

Outside Screw and Yolk

Question 55

What are two major advantages of the OS&Y valve?

Answer 55

The valve stem threads do not come in contact with fluids. Easier to maintain and lubricate.

Question 56

What is the purpose of a stuffing box?

Answer 56

To hold packing which prevents fluid leakage.

Question 57

What is the purpose of a packing nut?

Answer 57

To hold the packing gland and packing.

Question 58

What is the purpose of a packing gland?

Answer 58

To compress the packing.

Question 59

What is the purpose of a lantern ring?

Answer 59

To lubricate the valve stem.

Question 60

What special feature might be required for a gate valve installed in a vertical line?

Answer 60

Drain valve tapping above the disc.

Question 61

What flow condition could be reduced or eliminated with the use of a spring loaded check valve?

Answer 61

Water Hammer

Question 62

What is required in most plants before any component can be removed from a system or a piece of equipment?

Answer 62

Safe Work Permit

Question 63

What group is still considered to be at the forefront in setting valve standards?

Answer 63

MSS

Question 64

Why would a piping system built to B31.3 standards require a valve built to the API 6D valve standard?

Answer 64

A bubble tight seal is required between the disc and seats.