Choices can become overwhelming when selecting a valve for an instrumentation system. To name a few, there are; check valves, excess flow valves, needle valves, ball valves, relief valves, control valves, diaphragm and bellows valves. All of these are available in many configurations, materials, sizes and actuation types, making thousands of possible combinations.  

 

Have you matched the valve type to its function?

Matching the required function to the valve type is the vital first step in the safe selection process. It can be detrimental for systems and end users if the correct valve is not specified. For example, if a check valve is not installed downstream of a critical pressure regulator or control valve, a burst of back pressure could cause major damage to the equipment.

 

Is your valve for critical environments?

Valve packing prevents the process media from escaping into the atmosphere where the valve body meets the stem. The cylindrical stem is surrounded by a packing material. Valves that require packing must be replaced or serviced regularly, however some valves last longer than others depending on the seal material and process conditions. Always ensure you correctly choose a seal material by checking the chemical compatibility with your media.

On the contrary, the “packless” diaphragm valve provides swift shut-off and rigorous actuation speeds. Usually, diaphragm valves are specified in high-purity applications in the pharmaceutical and semiconductor industries. Each valve holds a thin film plastic or metallic diaphragm ensuring a leak-tight seal.

Similarly, there is also the “packless” bellows valve. This is a great choice when an atmospheric seal is vital and access for maintenance is restricted. You would often find these valves operating in nuclear power plants. The inlet is entirely sealed by a metal bellows that moves up and down, fixed to a non-rotating stem.  

Diaphragm and Bellows Valves

 

Is flow control essential?

Flow control valves have a rotating handle that allows the operator to control the system flow rate. The operator can adjust the valve to accurately hold at the desired flow rate. Needle, metering and plug valves are all frequently used for reliable flow control in systems.

Needle valves provide exceptional flow control and leak-tight shut-off characteristics. They have a long stem and are available with a few different highly engineered stem tips, including metering, regulating and shut-off (vee type). 

Our needle valves are often used for severe service in harsh oil and gas, chemical and petrochemical and power applications. Depending on construction materials and operating pressures, these can also be used for cryogenic service.

Fine metering valves should be considered for the most precise flow control. They have a thin stem that lowers through a narrow channel, making it perfect for controlling fine graduations of flow. These are typically found in laboratory environments.

Flow Control Valves

 

Is directional control required?

Check valves or 3-way ball valves should be considered for directional control of flow. Within check valves, a spring-loaded poppet is opened by the upstream fluid force, allowing flow through. In the event of a back pressure build up (increase in downstream pressure), the reverse flow is stopped by the poppet being forced back into the seat.

In many 3-way ball valves, the media enters through a single inlet and is directed to the outlets based on the selected flow path. Common flow paths include quarter turn switching, tee flow on/off and tee flow switching.

Excess flow valves stop the uncontrolled release of expensive or hazardous media into the atmosphere in the event of downstream equipment failure. Our excess flow valves utilise magnets to operate a reed switch and can be easily adjusted to the required flow set point. Utilising magnets to operate the unit allows for a completely unimpeded right-angle flow.

Directional Control Valves

 

Something more standard?

Quarter-turn plug valves and standard 2-way ball valves are both economically priced utility valves. Applications with either simple on/off functionality or pressure throttling commonly will use these valves.

Pressure relief valves can be found in almost any application and are used to protect sensitive equipment. These can either vent to atmosphere or be piped away safely.

Standard Valves

 

Still unsure what you need?

Once the valve type has been matched to function, you are on the right path in the valve selection process. However, many details remain. If you need advice and guidance on selecting the right valve, contact us today and we’d be more than happy to help.

Alternatively, take a look at our full product range here.