How to Select the Right Valve for Your Application

The right valve optimizes application performance and enhances operator safety. Valves come in a variety of shapes, sizes, configurations, materials and actuation. That can make the selection process confusing and time-consuming.

Here are some factors to consider when deciding which valve is right for the job.

Media Type

Your valve must be compatible with the media used in the application. Incompatible media and valve materials may cause premature failure or safety risks, resulting in costly repairs, replacements or even danger. For example, you may need a stainless steel valve materials if the media or environment contains corrosive or harsh chemicals.

The temperature of the media also influences your selection. You need to know if the media temperature will be constant or vary as that change can cause components to expand or contract.

Most manufacturers state the materials of the valve offer a variety of materials

Operator Type

The operator type differentiates what opens and closes the valve component.  A valve can be operated electrically, manually, mechanically or with a remote air signal.

Types of operators include:

• Solenoid: A coil is energized via an electromagnetic current that pulls an armature or plunger against a spring to open or close the valve.
• Detented lever: Detents or notches in the valve hold the opening in a fixed position to start, stop or control flow.
• Button: A push button activates the valve to allow flow through the opening.
• Foot operator: A floor mounted pedal activates the valve.
• Plunger: A piston or plunger moves inside the valve cylinders to control fluid or gas flow.
• Roller cam: The user’s work piece engages the cam actuator to switch the valve.
• Air pilot piston: This type of valve uses pneumatic pressure to operate.

Valve Function

What do you need your valve to do? What function must be completed during actuation?

The answers to those questions will help you determine what type of valve is right for the job. Valves start, stop, regulate, redirect and manage the pressure of media flow.

Valve functions include:

• 2-way normally closed: Two ports, IN & OUT. Media is blocked from passing IN to OUT through until activated.
• 2-way normally open: Two ports, IN & OUT. Media is passes IN to OUT until activated to block flow.
• 3-way normally opened or closed: Three ports (IN, OUT, EXHAUST). Same as 2-way, however OUT port is open to EXHAUST port when IN port is blocked.
• 3-way multi-purpose (universal): Valve functions as normally closed or open, as a two pressure selector or as a diverting function.
• 4-way, 2 position: Four or five ports, IN, OUT1, OUT2, EXH (1 or 2). Flow is directed IN to OUT1 while OUT2 is open to EXH(2). When activated, flow is directed IN to OUT2 while OUT1 is open to EXH(1).
• 4-way, 3 position: Same 4-way, 2 position, but with third “center” position. Center position can be configured for all ports blocked, IN to both OUT ports, both OUTs open to EXH.

Size

The size of the largest restriction within the valve (i.e. valve orifice) will influence how much media the valve can deliver in a given period of time. The larger the orifice, the greater the flow capacity.

A valve that is sized correctly delivers an appropriate volume of media within an acceptable period of time. An undersized valve may be small and affordable but will lack sufficient flow capacity. An oversized valve may have sufficient flow capacity but is physically large and typically more expensive.

Most manufacturers offer a variety of sizes and “categorize” them to assist the customer. For comparison purposes, most manufacturers have adopted a measurement known as flow coefficient (Cv) to assist the customer:

• Miniature: <0.1 Cv
• Small: 0.1-0.3 Cv
• Mid-size: 0.3-2 Cv
• Large: 2-4 Cv
• Very large: >4 Cv

Other Questions in Valve Selection

• What is the media and ambient temperature environment for the valve application?
• Is the ambient environment clean/benign or more difficult (dirty, dusty, wet)?
• Is the quality of the media controlled or is neglect possible, i.e. contain impurities?
• How will you mount, pipe and/or connect to the valve?
• Are there regulatory requirements that must be complied with?
• What is the operating voltage (solenoid valve applications)? 

Find the Right Valve at Humphrey Products

If you’re not sure how to answer those questions, talk to a Humphrey representative for assistance. We have been designing and manufacturing valves since 1960. Our expert team can help you determine what type of valve will provide optimal performance in your application. Browse our products, then contact our team for more details.