Valves Flashcards
What type of valve material should not be used where mechanical forces are transmitted to the valves or fittings?
Broze
It work hardens.
What four things must be clearly identified on valves?
- OEM marking
- Service ratings (pressure and temp for which the valve is designed)
- Material type
- CSA marking
What are the two ratings commonly found on valves?
- Steam rating
- Water, oil, and gas (WOG) rating
What is another name for the WOG rating of a valve?
The cold working pressure (CWP) rating
True or false: The steam rating of a valve refers to pressure.
True
As steam pressure rises, the temperature also rises.
How is the steam rating of a valve displayed?
With a number followed by the letter S
125S, 300S, etc.
What is the working steam pressure (WSP) of a valve?
The same as the steam rating
What does the marking 150WSP indicate on a valve?
The working steam pressure (WSP) of the valve.
If a valve has a WOG rating, what ambient temperature is its rating based on?
-20°F to 100°F
These are displayed on the valve with a pressure and WOG or CWP.
This type of valve consists of a disc diven up by a threaded stem and hand wheel.
A gate valve
What are the two varieties of gate valves?
- rising stem
- non-rising stem
- Can gate valves be used for throttling?
- Why or why not?
- No
- It will cause wire drawing on the gate and seats
How should gate valve be mounted in respect to the orientation of the bonnect assemblies?
The bonnet assemblies should be facing upwards.
Why do gate valves have a low resistance to flow with a minimim pressure drop?
The fluid flows through a gate valve in a straight line.
True or false: With gate valves, the non-rising stem moves up through the handle when the valve is opened.
True
What type of material would be used with valves subjected to low pressure, temperatures below 550°F and where no mechanical force is transmitted to the valve.
bronze
What type of material would be used with valves where the threaded fittings and valve that may be subjected to thermal or mechanical shock and stress.
malleable iron
What type of valve material would be used in corrosive service.
Stainless steel
What type of material would be used with valves and fittings subjected to high temperatures, pressures and other adverse conditions.
Steel
What type of valve material would be used with valves subjected to low pressure, temperatures below 450°F and where no mechanical force is transmitted to the valve.
Cast iron
This type of valve consists of a tapered or straight cylinder with a fluid passage hole through it, which results in a straigh fluid flow path resulting in a very low pressure drop.
A plug valve
What type of valve regulates the flow of liquids, including suspended solids (slurries) and viscous fluids?
A plug valve
What type of 1/4 turn valve would be used in water treatment plants and in pulp, paper and the chemical industries?
Plug valves
True or false: Ball valves can be used for throttling flow for short periods, but are designed for on/off applications.
True
These are 1/4 turn valves that require no internal lubrication.
True or false: Butterfly valves cannot be used for throttling.
False
They can be used for throttling.
What are four advantages of butterfly valves?
- low pressure drop across a fully open valve
- easy to operate
- relatively lightweight
- compact
Why is accurate alignment critical for butterfly valves?
To prevent binding of the pivoting disc
This disc swings into the pipes when open.
This type of valve is used for precise fluid control, and are often found in continuous air bleed or for chemical feed control applications.
A needle valve
What is the best type of valve for throttling flow?
Globe valves
This type of valve causes the flow of the fluid passing through it to change direction twice.
A globe valve
This type of valve sealing design minimizes wire drawing and seat erosion (metal wear in the valve due to product flow or debris caught in the valve seat).
Globe valves
What is the pressure drop on a globe valve?
High
This is due to the fluid flow changing direction twice as it flows through the valve.
What is an unbalanced single disc globe valve?
Where the full fluid pressure in the valve acts on the sealing plug, making it difficult to open or close.
What sizes are unbalanced single disc globe valves limited to?
12 inches (305mm)
True or false: Angled valves are the same as standard globe valves, but are used when a 90º direction change is required.
True
These valves have a reduced turbulence, flow restriction, and pressure drop.
What is the benefit of a balance globe valve vs. an unbalanced?
Balanced requires less force to open and close the sealing plug
This results in smaller actuators needed to open and close the valve.
What are the two designs of balanced globe valves?
- single seated balanced valves
- double seated balanced valves
This type of balanced globe valve allows equal pressure on both sides of the controlling plug while passing fluid.
Single seated balance valves
These valves are hydraulically balanced.
This type of balanced globe valve divides the flow to upper and lower plugs, with the two forces nearly balancing each other out.
Double seated balance valves
These valves are hydraulically balanced.
What type of globe valve has two flow paths through the valve?
The double seated balance valve
This type of valve is used for throttling corrosive and toxic fluids, and finds extensive use in raw water treatment, handling sulphuric acid, and applications requiring bubble-tight or drip-tight closure.
A diaphragm valve
What are the three basic parts of a diaphragm valve?
- Valve body
- Valve bonnet assembly
- Flexible disc or diaphragm (the closing element)
On a diaphragm valve, the ________ is the partition that separates the valve’s working parts (bonnet) from the fluid being handled.
diaphragm
This is also the valves dynamic sealing element.
True or false: The diaphragm movement mechanism is completely separated from the fluid, and no packing material is required to seal it off.
True
The lack of packing is an advantage over other types of valves.
What two things cause check valves to close?
- Reverse fluid flow
- Gravity
Ensure that these are installed in the direction of flow (⟶)
What are the two basic types of check valves?
- swing check valves
- lift check valves
This type of check valve has an almost straight line of flow and offers little resistance to flow or pressure drop.
Swing check valves
True or false: Swing check valves have a lower resistance to fluid flow than the lift check valve does.
True
This type of check valve changes the fluid flow twice as it passed through the valve.
A lift check valve
This valve will have a greater pressure drop than a swing gate check valve
This type of valve is designed to prevent damage and potential danger to worker in the event of unintentioal excess pressures in a fluid circuit.
Over-pressure safety valves
What is the cracking pressure of a pressure relief valve?
The pressure required to first open the valve
What is the full flow pressure of a safety relief valve?
The pressure required to fully open the valve
This can be up to 20 times higher than the cracking pressure
What is the pressure override of a pressure relief valve?
The pressure difference between the cracking pressure and the full flow pressure.
What is the reset pressure of a pressure relief valve?
The pressure to reseat the valve
This is just slightly lower than the cracking pressure
This type of pressure relief valve is comprised of a disc held in place by flanges, and is usally made of aluminum, stainless steel, or copper.
Rupture disc relief valves
These are designed to rupture at a preset pressure, and are single use only.
This type of valve provides a rapid means of getting rid of excess pressure in piping systems that can cause serious accidents.
Pressure safety valve
These are also known as pop valves
What types of fluids are pop valves used with?
Compressible fluids such as gases and steam
Pop valve = pressure safety valve
The compressibility of these gases necessitates rapid overpressure reduction. z
Pop valves are equipped with a huddling chamber.
1. What is this?
2. What is its purpose?
- A chamber where steam or gas collects.
- Allows adjustment of the valve pressure and the amount of blowdown after it pops
Blowdown = venting action of the valve exhaust
This type of valve control is used for throttling flow by providing a signal that is compared to the actual positon of the valve.
Valve positioners
What are three functions valve power actuators are used for?
- remote operation
- operation of large valves (considerable force required)
- automatic operation (the valve is part of an automated process)
What are three power methods that valve power actuators are operated?
- pneumatic power
- hydraulic power
- electric power
What is the most common power activation method used with valve power actuators?
pneumatic power
These include cylinders and diaphragms
True or false: A pneumatic cylinder may operate valves with sliding stems (globe or gate) or quarter turn valves (ball, plug and butterfly valves).
True
This type of pneumatic valve actuator usually operates a sliding stem valve.
Pneumatic diaphragm actuators
Air pressure is applied to one side of the diaphragm to move the valve one way, and a spring returns the valve (and diaphragm) to the other position.
This type of pneumatic valve control is accomplished with a cylinder-operated rack and pinion drive system.
Rotary pneumatic control
What type of pneumatic valve control would be used on valves requiring more than 90º to operate (three-way and four-way valves)?
Rotary pneumatic control
This type of hydraulic actuator would be used for valves requiring multiple turns to open and close, and has infinite position in the actuators operating range.
A hydraulic motor
True or false: A leaking valve stem can often be fixed by slightly tightening the packing nut or packing flange.
True
Occasionally applying a few drops of oil onto the valve stem and any exposed threads can greatly extend the life of valve packing. When is this not recommended?
With oxygen service
What is a globe valve composition disc?
The sealing disc is made of a selection of materials suited for specific purposes.
True or false: Bluing is used to check the contact percentage between the valve and seat.
True
Why is it a good idea to replace the disc in a globe valve at the first sign of damage?
This can save the seat from being damaged
What process can be used to repair a valve seat?
lapping
If severe damage is found, the seat may have to be refaced with a reseating tool.
True or false: When testing a valve, if a valve handles a hard to hold fluid (such as glycol or ammonia), the valve must be tested with a hard to hold fluid.
True
What are two designs of operation that are used to actuate valves?
- rotary
- linear
What are two advantages of using hydraulicly actuated valves?
- operate heavier loads
- more precise control
What are four types of NDT procedures used on valves?
- dye penetrant
- magnetic particle
- radiography
- ultrasonic
What damage is done to a plug valve if not lubricated?
Galling
A valve marked 125S means?
1) 125 psi sour service
2) 125 psi safe working pressure
3) 125 psi maximum pressure for steam
4) 125 psi swing safety
3) 125 psi maximum pressure for steam
A valve marked 125WOG means?
1) 125 psi maximum operating pressure water, oil and gas
2) 125 psi maximum operating pressure steam
3) 125 psi waste pressure product
4) 125 GPM water or gas
1) 125 psi maximum operating pressure water, oil and gas
Which valve is used to prevent equipment damage in the event of accidental over-pressure and is designed for non-compressible fluids?
Pressure relief valve
Which valve is suited to provide a rapid means of getting rid of excessive pressure of a compressible fluid?
Pressure safety valve
When repacking a valve stuffing box split ring packing you must ensure?
1) None of the splits line up
2) All splits line up
3) The spindle is removed
4) Never to apply oil during this procedure
1) None of the splits line up
Which term is used when resurfacing two mating surfaces of a valve to make the parts fit each other precisely?
Lapping
Which method of inspection of a valve is used to find cracks or flaws?
NDT testing
What does the term” backseat feature” mean on a valve?
The seal made on a check valve
Why is routine inspection and adjustment of pipe hangers part of valve maintenance?
To reduce mechanical stress on the valve
Identify the valve shown:
Swing check valve
Identify the valve shown:
A gate valve
Identify the valve shown:
A butterfly valve
Identify the valve shown:
Lift check valve
Identify the valve shown:
A globe valve
True or false: Valve actuators can change the position of a valve either by a linear or rotary movement, and can come in either fail-open or fail-closed control valve actions.
True
