Section Three Valves

Question 1

What is the purpose of a valve?

Answer 1

To stop or start flow, or to regulate flow.

Question 2

Regulation of flow includes:

Answer 2

Throttling, prevention of flow reversal, and relieving or regulating pressure within a system.

Question 3

There are eight basic valve designs available. Name all eight.

Answer 3

Gate. Globe. Check. Diaphragm. Ball. Butterfly. Plug. Relief.

Question 4

How should a gate valve be used?

Answer 4

For on or off service either fully open or fully closed.

Question 5

Why are gate valves either fully open or fully closed?

Answer 5

Because of excessive vibration and wear created in partially closed gates valves are not intended for throttling or floor regulation.

Question 6

What kinds of gate valves are available?

Answer 6

Solid wedge. Flexible wedge. Split wedge and double desk styles.

Question 7

What service is the wedge type gate valve used for?

Answer 7

Suitable for air. Gas. Oil. Steam. Water.

Question 8

When installing either a split wedge or double desk gate valve, the stem of the valve must be in what orientation?

Answer 8

Vertical.

Question 9

How should a globe valve be used?

Answer 9

Globe valves, unlike gate valves, are used in applications requiring frequent operation and or throttling of flow.

Question 10

Globe valves are available in three body styles name all three.

Answer 10

Angle body. Y pattern and T pattern. Straight way (most common).

Question 11

What do angle body valves provide in terms of direction of flow?

Answer 11

90° change of direction.

Question 12

What angle does the stem of a Y pattern globe valve protrude from the body?

Answer 12

45 or 60°.

Question 13

The Y pattern globe valve is ideally suited for applications requiring almost:

Answer 13

Full flow in a valve but with the characteristics of a globe valve.

Question 14

Applications for Y pattern globe valves include:

Answer 14

Boiler blowoffs and services where mud grit and or viscous fluid’s may be encountered.

Question 15

The main types of globe valves according to their seat arrangements are:

Answer 15

Conventional disk. Plug disk. Composition disk. Needle valve.

Question 16

Conventional desk globe valves use a what?

Answer 16

Short tapered disk for closure and throttling.

Question 17

When is a conventional disk globe valve preferred?

Answer 17

When flow conditions have a tendency to deposit coke on valve seats.

Question 18

How does the plug disc differ from the conventional disc Globe valve?

Answer 18

The plug disc and seat arrangement are longer and more tapered. The longer area of the plug and seat give the plug maximum resistance to flow induced erosion.

Question 19

Needle valves are designed for small diameter lines requiring what?

Answer 19

Fine throttling of gases, steam, oil, water, or any other light liquid

Question 20

What service are check valves used for?

Answer 20

Back flow prevention.

Question 21

The two most common designs of check valves are:

Answer 21

Swing check. Lift check.

Question 22

How should a swing check valve be installed?

Answer 22

Installed so the swing check valves disc closes positively by gravity.

Question 23

What are diaphragm valves sometimes referred to and what service are they use for?

Answer 23

Saunders valves. Used to control flow for corrosive services were line content could abrasively affect the valve components And where outside contaminants are not tolerated.

Question 24

How can most diaphragm valves be classified as? Name both.

Answer 24

Weir type. Straightway type.

Question 25

Of the weir diaphragm type and the straightway diaphragm type valves which is the most common?

Answer 25

Weir.

Question 26

Pinch valves are another type of diaphragm valve. what services are pinch valves ideally suited for?

Answer 26

Suspended matter, slurries and solid powder flows.

Question 27

How should a ball valve be used?

Answer 27

Fully open or fully shut.

Question 28

Ball valves come in three general patterns name all three.

Answer 28

Venturi port. Full port. Reduced port.

Question 29

Aside from ball valve patterns they may also be classified by their body styles. What are their body styles?

Answer 29

One piece. Multi piece.

Question 30

How can a butterfly valve be used?

Answer 30

On off or throttling.

Question 31

Because of the advances in seating material, butterfly valves have found general acceptance in what services?

Answer 31

Oil, gas, chemical, water, and process fields.

Question 32

How should plug valves be used?

Answer 32

On off service.

Question 33

There are two basic types of plug valves available:

Answer 33

Lubricated plug. Non-lubricated plug.

Question 34

How do relief and safety valves work?

Answer 34

Automatically relieve excess pressure in pressure vessels or piping systems.

Question 35

In what situation is a relief valve used?

Answer 35

In applications were full discharge of pressure is not required to relieve excess pressure.

Question 36

How does a safety valve work?

Answer 36

Used to fully relieve pressure in the system of compressible fluids and gases which may cause an explosion went over pressurized.

Question 37

What is the primary function of a valve bonnet?

Answer 37

To provide for a pressure tight transition assembly from the valve body to the valve stem.

Question 38

There are four basic stem mechanism designs available for valves what are they?

Answer 38

Inside screw rising stem. Inside screw nonrising stem. Outside screw rising stem. Quick opening sliding stem.