Common Valve Types in Industry

The following list contains information on common basic valve types and uses encountered in a food or pharmaceutical processing facility.  Every design situation is unique and often there are several valve choices which could work for a particular design.  It is up to the design engineer to choose which type, size, trim, material, style etc. of valve is best suited to an application based on operating parameters, control characteristics, financial concerns, and maintenance concerns.

Also, many of these valves can be purchased with manual or automated actuators depending on the desired use.  Sizing and selection of actuators is also often required to fit within the overall control structure of a facility. 

The specification of even the most fundamental control elements of a piping system can have wide ranging impacts.  If you have an application requiring design of fluid process piping systems, Puffer Engineering Firm LLC can design the system as well as specify and bid out all the components required to construct it.

• Solenoid Valves: Solenoid valves utilize an electromagnet to translate electrical current into mechanical movement.  Solenoid valves always feature the electromagnetic coil around a moveable piston, but they may also feature a spring to return to a certain position upon removal of power, mechanical interlocks, and different numbers of sealing surfaces attached to the piston armature.  Solenoid valves can be used as a “pilot” valve to allow air or another media to flow and operate much larger valves, or they can be used as the primary control element themselves.  Solenoid valves are very customizable, but usually they can be divided into two main groups.
  • Poppet Valves- The armature of a poppet valve features a disc shaped sealing surface which is larger than the sealing orifice.  When the armature is moved, the sealing disc no longer occludes the orifice and fluid can flow.  These valves usually open and close faster than spool valves since fluid can flow even with a very small stroke length.  The primary disadvantage of poppet valves is that their sealing disc must be larger than the orifice 
  • Spool Valves- The armature of a spool valve features cylindrical “spools” which are slightly smaller than the main bore of the valve.  These spools typically feature elastomeric gaskets and as they travel up and down the bore of the valve they connect different ports of the valve together.  The primary benefit of this style of solenoid valve is that they typically can handle larger flow rates for the same bore size as the spools don’t occlude flow as much as the head of poppet valve.  These valves typically have longer stroke lengths than similar sized poppet valves, so they often have a longer actuation cycle.

• Check Valves: These valves prevent fluid flow in one direction
  • Swing Check- This is the most basic type of check valve, and it consists of a hinged swinging gate or disc which closes when it experiences flow in one direction.  Mounting orientation is important as in the absence of flow the disc is usually meant to close under the force of gravity.
  • Spring Loaded Disc Check- This consists of a disc which uses a spring to seal against the valve seat.  The pressure in the permitted direction of flow which causes the seat to start to open is often called the “cracking pressure”.
  • Sanitary Y-ball Check- This type of check valve is constructed to be free-draining and not have any harborage points if it is installed in the proper manner and orientation.  The sealing against flow is often accomplished with an elastomeric gasket and a PTFE ball which contact each other when backflow occurs.
  • Spring Loaded Ball Check- This type of check valve is similar to a spring-loaded disc check valve, but the sealing element is a ball.  These can be preferable in applications where there is some small particulate in the fluid stream as the ball can rotate freely which prevents particulate from getting stuck under the valve seat as sometimes occurs with spring loaded disc check valves.

• Ball Valves: Ball valves are often full port, though there are characterized seat options available for modulating applications.  Due to their design and method of sealing, ball valves often feature good service life and relatively high-pressure ratings for their diameter when compared to similar sized valves.  These valves feature a rotating ball with a hole in it which can usually be switched from full port open to full port closed in 90 degrees of rotation.  There are a myriad of trim options and styles available, but the primary types of ball valves are either:
  • Maintainable Ball Valves- These are usually multi-piece valves which allow for taking the valve apart and replacing seals when necessary.  They typically are held together with external bolts which pass through the valve body.  These are a good choice when welding the valve inline is necessary, as they allow the PTFE, plastic or elastomeric components to be removed and reinserted after welding is complete.
  • Non-Maintainable Ball Valves- The most common types are called two-piece valves and typically are meant to be threaded into a piping system.  In a two-piece ball valve the two halves of the body enclose the ball, valve seat, and stem and are typically screwed together with a great amount of force at the factory.  Valves of this style are typically meant to be discarded when their valve seat wears out.

• Gate Valves: These valves feature a large gate which is usually attached to a screw.  The gate usually can be fully retracted, allowing for full port fluid flow.  These valves usually take many complete turns of the operator or screw to be able to fully close or fully open, and there are different gate edge profile types available.  The most used style of gate valve is called “OS&Y”, which means it has an outside screw and yoke.  In this style, the screw shaft which raises and lowers the internal gate usually is sealed with stem packing and secured with a packing gland and nut.  This style of valve is often used in steam service as there are many options available which can handle the high temperature and pressure requirements, and the gate will not suffer damage from high steam velocity erosion if it is fully retracted (open). 

• Globe Valves: Globe valves are often an inexpensive option which can provide shutoff as well as some modulating capability.  They usually have a single piece cast body with two “hemispheres”, and the orifice between these two cavities is sealed by a disc or plug attached to the valve handle.  The handle screw is usually sealed by packing and a packing nut.  Fully opening or closing this style of valve usually requires multiple full turns of the operator screw.

• Butterfly Valves: Butterfly valves feature a disc which is almost the exact inside diameter of the piping and valve body which is always in the fluid flow.  The disc rotates such that in the fully closed position the flat face of the disc is perpendicular to the fluid flow.  When the valve is fully open the flat face of the disc is inline with the fluid flow.  There are single eccentric and double eccentric versions of butterfly valves as well as different disc mounting styles, but the primary advantage of these valves is their price.  They are usually cheaper than the other styles of valves in a certain range of intermediate diameters.  I usually use them in the 3” to 6” nominal diameter range.  The primary disadvantages of these valves are that they don’t typically yield a tight positive seal when used as hand valves, and that they tend to “weathervane” in a strong fluid flow.

• Plug Valves
  • Lubricated plug valves- feature an oil coated metal plug and are typically used on natural gas lines and other locations where bubble tight shutoff is required but the valve will be operated infrequently.  These valves usually offer little restriction to flow and quick shutoff capability, but frequent operation can require relubrication of the sealing faces.
  • Non-lubricated plug valves- typically feature a polymer seal between the plug and the plug seat/valve body.  These valves can be limited in service temperature by the polymer type used.

• Sanitary Piston Type Valves: These valves are typically used in processes requiring the highest standards of hygiene and cleanability of a piping system.  All surfaces exposed to product are typically free draining if installed correctly, non-porous, and chemical resistant.  These valves are designed for use in piping systems which utilize clean-in-place (CIP) procedures, but typically cannot be used in lines which require cleaning by “pigging”.  These valves typically are actuated by pneumatic piston, often with an internal spring return fail position, but can be actuated manually or by electric actuator.  These are sometimes called “piston type” valves since they typically accomplish sealing with a flat piston driven disc against an orifice which is typically full port diameter.
  • Sanitary Single Seat Valves- As the name implies, these valves usually have only a single elastomeric or polymeric seal on the sealing disc to prevent liquid flow and if that seal is compromised then flow can occur across the valve seat even if the valve is in the closed position.
  • Sanitary Double Seat Valves- These valves usually feature two sets of elastomers for sealing, such as an upper and lower seat seal.  The second seal gives redundancy and can be considered adequate separation in low hazard cross connections where there is no chemical or biological danger.
  • Sanitary Mix-Proof Valves- These valves also feature two sets of elastomers for sealing, but they also feature an atmospheric vent chamber between the two sealing surfaces.  One valve gives true “double block and bleed” protection between the ports it is separating.  In a CIP procedure with the valve closed, the seating surface exposed to the upper ports can be cleaned independently of the seating surface exposed to the lower ports by temporarily moving each surface slightly open to allow cleaning fluid to flush the surface down through the atmospheric vents.

• Pinch Valves: These valves feature a flexible liner which is deformed by the valve in operation to occlude flow through the valve.  Two common applications for these valves are:
  • Inline Explosion Isolation Valves- These are a specialty type of pinch valve which can close fully within milliseconds of receiving a signal to close.  They typically function by rapid filling with compressed air or nitrogen.
  • Flow shutoff or control for sanitary applications- The benefit of these style of valves is that they often are full port and usually offer very few places for bacterial harborage since the area exposed to product flow is usually a hollow elastomeric sleeve.  These valves also are typically considered self-cleaning in a CIP circuit.