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Various types of valve advantages

Writer:condiSource:Network Date:2017-2-9 09:37

 

Type

Description

Advantages

Disadvantages

Gate valves

   

Image Credit: Cameron

Linear motion valves used to start and stop flow. The valve is completely opened when the disk is removed from the flow stream. Classification of gate valves is made by the type of disk used: solid wedge, flexible wedge, split wedge, or parallel disk.

No resistance to flow when open

Flow changes nonlinearly with stem travel

Little pressure drop

Vibration/cavitation when partially open

Good sealing when closed

Subject to wear

Little/no leakage

Repair work is difficult

Globe valves

  

Image Credit: Flowserve

Linear motion valves used to start, stop and regulate flow. The disk moves perpendicular to the seat to open or close the flow so the annular space between the disk and seat ring gradually changes. There are three body designs for globe valves: Z-body, Y-body, and angle and three designs for the disk: ball disk, composition disk, and plug disk.

Throttling and regulating flow

High head loss due to flow direction changes

Less seat leakage than Gate Valve

Dynamics can create pulsation and damage trim/packing/actuators

 

Noisy in high pressure applications

 

Valves can be very heavy/large in size for a given application

Ball valves

 

Image Credit: Cameron

Rotational motion valves used to start, stop or throttle flow. It uses a ball shaped disk with a hole in it. When the valve is opened the hole of disk is turned in-line with the direction of the flow. When the valve is shut, the ball is rotated so that the hole is perpendicular to flow direction.

Less expensive

Relatively poor for throttling

Low maintenance costs

Throttling leads to seat erosion

Low torque

 

Quick action on/off

 

Compact

 

No lubrication

 

Tight sealing

 

Plug valves

  

Image Credit: Cameron

Rotation motion valves used to stop and start fluid flow. The disk is a solid tapered or cylindrical plug with a bored passage at the right angle to the longitudinal axis of the plug. When open, the plug lines up with the inlet and outlet port of the valve body. The plugs are either round or cylindrical with a taper. Plug valves are easy to adapt

Rotational motion

Typically NOT for throttling

Suitable for multi-port designs

 

Diaphragm valves

 

Image Credit: Dharmi engineers

Linear motion vales that are used to start, regulate, and stop fluid flow. The disk is flexible and seals with the seat in an open area at the top of the valve body.

Well-suited for difficult environments (corrosive chemicals, slurries, radioactive fluids)

 

Ability to throttle

 

Reducing Valves

Automatic valves that reduce supply pressure to a preselected pressure. The supply pressure must remain at least as high as the selected pressure.

Automatically reduces supply pressure to preselected pressure

 

Pinch valves

 

Image Credit: Flowrox

The simplest of any valve design. Pinch valves consist of a sleeve molded of rubber or other synthetic material and a pinching mechanism. The pinching mechanism, a bar or gate, is lowered onto the valve body to cut off the flow through the system.

Relatively inexpensive

 

On/off as well as throttling/regulating

 

Good for slurries, solids

 

Well-suited for difficult environments

 

Butterfly valve

 

Image Credit: Cameron

Rotary motion valves that can be used in on-off and throttling systems. They are quick and easy to operate. The flow control element is on either a vertical or horizontal axis and is opened when the handle is rotated 90 degrees and closed when the valve is turned an additional 90 degrees.

On/off as well as throttle/regulate

 

Easily/quickly operated

 

Good for large flow/low pressure applications due to saving in weight/size/cost

 

Good for slurries/suspended solids.

 

Needle valves

 

Needle valves have a long, tapered, needle-like point that is used to make relatively fine adjustments in the amount of fluid flow. They are sometimes used as component parts for other valves because the needle allows for a gradual change in the size of the fluid flow opening.

Good for fine adjustment throttling

 

Check valves

 

Image Credit: Cameron

Check valves are used in systems employing gate valves because they prevent the reversal of flow in the piping system and there is a low pressure drop across the valve. The pressure of the fluid through the system opens the system, while the weight of the check mechanism will close the valve if the flow is reversed.

Prevents reverse flow

 

Relief and safety valves

Image Credit: Watts

A relief valve opens slowly as the pressure increases about the set-point and only opens as necessary. A safety valve rapidly opens as the pressure setting is reached and will stay open until the pressure is lower than the actuating pressure set-point. Both valves are used to prevent damage by relieving accidental over- pressurized fluid systems.

Prevents over-pressurization

 

Relief valves are used for incompressible fluids such as water or oil

 

Safety valves are used for compressible fluids such as steam.

 

TypeInfo: Technical Articles

Keywords for the information:Valves  butterfly valves  ball valves  check valves  flanges  globe valves  pipe fittings