Plastic valves
Plastic valves are alternatives to metal valves.
They tend to be used in corrosive applications as, unlike metal valves, they are able to resist corrosion, rust, scale and any other forms of build-up. Being able to resist these forms of build-up is a huge positive and also means that plastic valves will have a longer lifespan than their metal counterparts.
Plastic valves also provide the benefit of remaining smooth as well as free of build up, when used in a corrosive atmosphere, meaning that the flow rates and pressure drops will remain the same even after years of use.
Another benefit of plastic valves is that they are resistant to airborne corrosives without the need for any special painting or coating, expanding the range of applications that they can be used in and their lifespan
Another benefit of plastic valves is that they are resistant to airborne corrosives without the need for any special painting or coating, expanding the range of applications that they can be used in and their lifespan
There are a multitude of plastics that can be used to create these valves and some will only be used when an applications requirements call for it. This can be anything from a temperature increase to a higher pressure rating.
The plastics listed here cover a range of applications and would be used in various applications for their different properties:
Valve body materials: PVC, ABS, PVC-V or Polyproplene.
Seal materials: NBR, EPDM, PTFE, Viton.
(Please note: there are many more plastics and materials that could/would be used in plastic valves or their seals, these are just a select few).
Body materials:
Body materials:
- PVC: is the most prevalent plastic valve material used. It covers a wide range of applications such as; Chemical processing, wastewater treatment, industrial plating and electronics manufacturing.
- Teflon: would be used for ultra-pure applications. This material is selected because of its non-leaching properties, resistance to adherence and subsequent growth of organic impurities.
- Teflon PTFE: would become popular when an application calls for a higher temperature or pressure rating.
- Polypropylene: is another popular material that would be used in better quality plastic valves.
- ABS: is a popular plastic for compressed air applications although its capabilities compared to a metal valve mean that it is only generally used if the life and safety of the valve is affected due to atmospheric conditions.
Seal materials:
- NBR: is one of the most common solenoid valve seal materials. It could possibly be considered the standard material for neutral fluids. NBR could stand temperatures of up to 90°C.As well as being used for solenoid valve seals, NBR can be used for; Water pumps, carburettor, transmission, hydraulic pump and hydraulic actuator seals.
- EPDM: stands for Ethylene Propylene Diene Monomer rubber. EPDM is suitable for use in applications where the media is hot water due to EPDMs resistance to heat. EPDM can serve in application of up to 120°C. However, EPDM is unsuitable for use in applications with oils and fuels.
- Viton: is well known for its heat resistance. This high resistance to heat means that Viton can be used in applications where the temperature could reach 150°C.
- PTFE: could be considered practically resistant to all fluids. It is non-elastic, this is a downside as it limits the amount of applications that it can be used in. PTFE can be used in applications where the temperature could reach 230°C.
Below is a
table showing which seal materials can be used with certain media. It also
shows what the material has a good and bad resistance to:
Material
|
Can
work with
|
Good
resistance to
|
Poor
resistance to
|
NBR
|
|
|
|
EPDM
|
|
|
|
Viton
|
|
|
|
PTFE
|
|
|
The design of plastic and metal valves is relatively similar. Examples of the similarities would be the ball, butterfly and globe valves which seemingly have no differences other than their materials.
Plastic valve bodies are generally threaded or cemented together, or assembled with fasteners.
For mass production of plastic valves, a process called injection moulding is used. This is similar to the casting of metal valves. Injection moulding involves injecting raw material into a mould to create an item or part, in this case a valve. This process is cost-effective, reliable and efficient.
Injection moulding is effective for high quantities of products. The results are consistent and this makes it ideal for producing large quantities of the same item at affordable prices.
Plastic valves tend to be relatively easy to service as they do not require any unusual tools or equipment to disassemble the valves.
With design considerations the seals and key parts can be replaced in the field with minimal downtime.
The ease of installation does have drawbacks. Some plastic valve defects are caused by too much force when being installed.
Plastic valves don’t require much force and usually should be hand tight, but potentially adding a half turn with a wrench.
However, the valves do not require a lot of force and can be damaged if tightened too much. This can happen as the valve will be placed under stress and If the valve is under prolonged stress conditions then it can cause the valve to become defective.
V-Flow Solutions offers a wide range of plastic valves, including: Plastic manual valves, Plastic actuated valves and Plastic solenoid valves.
You can view the V-Flow Solutions range of plastic valves here:
You can read the rest of V-Flows blogs here.
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We will be covering different types of valves in future blog posts.
Other types of valves and products can be found here, on our website:
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If you think V-Flow can help you then please contact us:
Telephone: +44 (0)1234 855888
Email: sales@v-flowsolutions.co.uk
Fax: +44 (0)1234 857775
V-Flow are the experts of flow control.
If you have a problem with flow control, we will find the solution.
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