Valves Level 1 - Garlock Fluid Sealing Academy
Valves: Level 1 Training
This course is designed to provide a basic understanding of the different types of valves available, what a butterfly valve is, the different types of butterfly valves, how to install a valve, and the different methods to actuate the valve. The Level 2 module will outline the advantages of the GAR-SEAL® valve and what sets our valve apart from the competition.
What is a Valve?
A valve is a device that is able to control, shut off, direct, or regulate the flow inside a pipeline by obstructing its flow direction, partially or completely, depending on the type of application.
- Pumps are used to propel media through a pipeline, or increase the rate of flow of the media
- Valves can reduce or stop the rate of flow of the media
Check vs. Quarter Turn vs. Rising Stem
Check valves allow the media to only flow in one direction and automatically prevent backflow (reversing direction).
Check valves work automatically and don’t require assistance to open or close.
They are used on household sump pumps–they allow the pump to expel the water out of your basement and yet don’t allow the water to come back down the pipe
Quarter Turn Valves
Quarter turn valves work on a simple principle where you turn the handle (and stem) a quarter of the way to open or close the valve. Common types of quarter turn valves are ball valves, plug valves, and butterfly valves.
Rising Stem Valves
Rising stem valves have a threaded stem which is rotated to open or close the valve. As the stem is rotated, it raises or lowers the valve closure mechanism to allow media through or to close off the valve. Common types of rising stem valves are globe valves, gate valves, pinch valves (diaphragm valves are a type of pinch valve), and needle valves.
On/Off Valves Vs. Control Valves
On/off valves are used to either allow the media to flow through or to stop the media. They can be used to limit the amount of media going through the pipe; however, that is not their most efficient use and can even damage the valve. All valves can be used as on/off valves, but not all valves can be used as control valves. Gate Valves and Plug Valves should only be used as on/off valves and should not be used as control valves.
Control valves are used to control or limit the rate of flow. They are often attached to an electric or pneumatic actuator, which makes frequent, small adjustments to precisely control the amount of media going through. Rising stem valves are typically used as control valves because the rotating operation is slow and stable, making it easier to accurately control or limit the amount of media going through the pipeline. Except for Gate and Plug valves, most valves can be used to control the media; however, some are more efficient than others. The most common type of control valve is the Globe valve.
Ball and Gate valves are commonly used in home water pipelines. Note that the type of handle (green lever or red handwheel) may change; however, lever handles are normally only used with quarter turn valves. Garden hose valves are typically gate valves, so the flow of water can be controlled.
About Butterfly Valves
Quarter Turn, On/Off Butterfly Valves
While butterfly valves can be used to limit flow, they are typically used as on/off valves. Most companies will publish “Cv” rates for butterfly valves showing the rate of flow at various disc angles.
Face to Face
Butterfly valves are unique in that, while the outer diameter (OD) of the valve increases with the pipe diameter, the face to face (depth or thickness of the valves) remains somewhat constant. The face to face increases from 1.5-6” (38-152mm) as the pipe diameter increases from 2-24” (40-600mm). Ball, Plug, Globe, and Gate valves can range from 7-50” (178-1270mm) as the pipe diameter increases from 2-24” (40-600mm).
Advantages and Disadvantages of using a Butterfly Valve
- In the bigger sizes, >2” (DN50), butterfly valves are lighter, smaller, and cheaper than competing Globe, Gate, Ball, and Plug valves.
- Butterfly valves most often compete against Ball valves in the smaller sizes, <4” (DN100).
- Butterfly valves are not “piggable”, because the disc intrudes into the pipeline.
- Pigging a pipeline occurs when you send a device (often foam) through the pipe to clean it.
- The disc will reduce the amount of flow going through the pipeline. Other types of valves (Ball, Gate, etc.) do not have this issue.
Types of Butterfly Valves
There are 3 main categories of butterfly valves: Rubber-lined, Plastic-lined, and Metal.
Garlock does not offer rubber or metal valves, so our main focus will be on plastic-lined valves; however, a lot of the main concepts apply to all 3 types.
- Less expensive valves for non-demanding, non-abrasive, lower temperature applications
- Normally for 150-300# (PN10-25) flanges
- For use with harsh chemicals, ultrapure applications, sanitary, or abrasive applications
- Normally for 150# (PN10/16) flanges
- The GAR-SEAL® valve is a Plastic-Lined valve
- For high-pressure or high-temperature applications, or those requiring fire resistance
- Can be used in 150-2500# (PN10-160) flanges
- Can be Single Offset, Double Offset, or Triple Offset
- Has bolt holes to connect with pipe flanges.
- Because it has threaded bolts around the entire area, the lug valve is a safer option—most customers can switch from a wafer valve to a lug valve; however, they cannot switch from a lug to a wafer.
- Lugs can be used as a pipe ends or as end-of-line service.
- With some lower-strength body materials, the lug threads are weak; therefore, lug valves may have lower bolt torque ratings than wafer.
- Garlock only offers wafer and lug type valves; the bolt torques are the same for both types.
- Features two or more centering holes to help with installation.
- Is lighter and cheaper.
- Cannot be used as a pipe end or as end-of-line service.
- Garlock only offers wafer and lug type valves; the bolt torques are the same for both types.
- Has a flange face on both sides of the valve.
- Popular in the very large size valves.
- Some companies use a ‘U’ shaped valve–this is cheaper; but the two flanges are not always parallel, which can cause problems with bolting against the pipe flanges.
- Garlock does not offer this type of valve.
- Used for very-high-pressure applications.
- Because most plastic lined valves are limited to PN10/16 (150#) flanges, this type is rarely seen with plastic-lined valves.
- Garlock does not offer this type of valve.
There are three main ways a disc can be aligned in a valve: zero offset, double offset, or triple offset.
Most plastic lined valves are considered zero offset. Most metal valves and some rubber-lined valves are double or triple offset. Garlock valves are all considered zero offset.
Butterfly Valve Installation
When installing butterfly valves, you want to have the disc open slightly (Garlock recommends 10° open) to reduce the pressure on the valve body. Generally zero offset valves can be installed in either direction. With double and triple offset valves, it is important to install the valves correctly.
For abrasive applications, it is recommended that zero offset valves are installed horizontally to minimize the abrasive media contact with the stem seal.
For lined valves, you normally do not need to use a gasket, because the liner acts like a gasket on both sides; however, if your flange surface finish is rough, we recommend using a softer PTFE gasket to prevent damage to the liner. Otherwise, the use of a gasket is not recommended.
The liner on the valve essentially turns the valve flange into a raised face. If installing against a flat face pipe flange, it is recommended to use a flange spacer to protect the flat face pipe flange. Most flat face flanges are meant to butt up against another flat face–when butting up to a raised face, it can create bending stresses on the flange as it is tightened against the raised face valve. A flange spacer is like a gasket with a big inner diameter (ID)–it will sit outside of the liner, turning the raised face valve flange into a flat face.
If attaching a metallic valve to a non-metallic pipe, please check with your piping engineers to ensure that the non-metallic pipe will not be damaged with the weight of the metallic valve. The same guidelines apply if the non-metallic pipe is flat face or has limited torque recommendations.
If your pipe schedule is very low (i.e. your pipe wall is very thick), please consult with engineering; depending on the size and thickness, the disc of the valve could hit the pipe wall ID.
When installing a valve into a pipeline, be sure to use the recommended bolt installation torques, which are listed in the Operating and Installation Manual that comes with every valve. Please ensure that your pipe and bolts are capable of meeting these recommended torques. (The lug valves have threaded holes, which are offered in US or DN standards.)
More commonly when discussing torques, people refer to the torque needed to open or close the disc; these torques are used to determine which actuator to use and are located in the technical manual.
KV or CV rates give the amount of fluid (water) that will flow through a valve with a pressure difference of 1 bar given the opening angle of the disc. In a pipeline with an open butterfly valve, as the fluid goes through the valve, the flow rate will decrease, because the open disc is blocking part of the passage. The KV or CV rates will show you exactly how much of a reduction in flow rates you will have, including the flow rate loss as the disc is at different open/closed angles. (KV rates in are m3/hr, and CV rates are in G/h. Tables are listed in the technical manual.)
Methods of Actuation
There are 3 main ways to actuate the valve (open or close the disc): Handles, Gear Operators, and Power Operated Actuators
Handles For Butterfly Valves
- Typically called levers or lever handles, these handles act like a wrench to open or close the disc (quarter turn) and require a person to turn them.
- Handles usually have teeth so that the disc can be opened in increments.
- They also have a dial showing whether the disc is opened or closed.
- Handles are used on smaller sizes only because the force required to actuate the disc on the larger sizes is too great to open manually.
- Some handles come with a lockable hole, which are called locking lever handles.
- Gears are used to reduce the force needed to open and close the valve (quarter turn).
- Traditionally, they come with a handwheel to facilitate easy operation and may be called handwheel gear operators. The handwheel is rotated, and the gear box translates that turning force to rotate the stem.
- They also have dial showing whether the disc is opened or closed.
- Gears are available on all sizes.
- Gears can be requested with a lockable hole, called locking gear operators.
- Gears can also be requested with a chain wheel, called chainwheel gear operators. The handwheel on these has a grooved slot for a chain to go through. The handwheel can still be rotated manually, or the chain can be pulled to rotate the handwheel. This type of gear is used in areas where the valve is not easily accessible–the chain will hang down a specified distance and allow the valve to be opened or closed when the valve is not within easy reach.
Power Operated Actuators
Actuators allow the valve to be opened and closed automatically or at the touch of a button. They are used when the valve needs to be frequently actuated, when easy actuation is required, or when better control is required.
There are three main types of actuators: pneumatic, hydraulic, and electric.
Pneumatic actuators require air to power the actuator and turn the valve stem. They come in two styles: Piston or Diaphragm. For butterfly valves, piston pneumatic actuators are much more popular than diaphragm.
Rack and Pinion
Rack and Pinion actuators use air to rotate the pinion over the liner gears. The forces applied to the stem are linear.
Scotch Yoke actuators use air to push move piston, which turns a yoke. The forces applied to the stem vary due to the curved shape of the yoke.
Diaphragm Pneumatic actuators
Diaphragm Pneumatic actuators use compressed air to move the diaphragm, which in turn rotates the stem.
Hydraulic Actuators work in a similar manor to pneumatic actuators, except they use hydraulic fluid instead of air.
Electric actuators use a power source to run the actuator. They usually include intricate electrical circuitry to program when the actuator operates.
Double Acting Vs.Single Acting Actuators
Most actuators fall into one of two categories: Double Acting or Single Acting.
Double Acting means that the air or hydraulic fluid is applied to both sides of the piston to both open and close the valve.
- Double acting normally applies to Pneumatic and Hydraulic Actuators.
- The danger of a double acting actuator is if there is a power outage; if the actuator loses power, it will stay in either the open or closed state it was last in (unless there is a manual handwheel).
Single Acting means the air or hydraulic fluid is used to either open or close the valve, and a spring is used to do the opposite action.
- Single Acting can apply to all three actuator types.
- If you have dangerous chemicals in the pipeline, you might want the valve to automatically close if power is lost. This is called a Spring Close or Spring Return.
- If you have fire water in the pipeline, you might want the valve to automatically open if power is lost. This is called Spring Open.
Actuators can come with various accessories: Below is a picture of a valve with the mounting kit, the actuator, positioner, and limit switch.
Limit Switches are used to swiftly show whether the valve is Open or Closed
Positioners are used to increase the accuracy of the valve position (open, closed, partially opened). They measure the actual valve position against desired position and adjust the valve until it is in the exact correct position. They are normally used on control valves to delivery precise throughput.
Solenoid Valves are used to direct airflow into and out of pneumatic actuators. They are used to remotely control actuator position using an electrical signal and remove the need for a person to operate the valve manually.
The handwheel option allows users to manually open or close the valve instead of relying on the actuator to do so.
To attach an actuator to the valve, you need a Mounting Kit–this typically includes a Mounting Plate and Coupling. The Mounting Plate bolts the valve to the actuator, and the coupling connects the valve stem to the actuator.
Conclusion and Test
This concludes the Garlock Pipe, Valve, and Pump Sealing Solution Training: Valves, Level 1 course. You may proceed to the testing portion.