Valves, just like engines, pumps, and compressors are essential components of various mechanical systems. The valve's performance depends on the proper functioning of its components, including the valve seat, which functions by ensuring proper sealing between the valve and the valve body.
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Source: IstockChoosing the right valve seat material is crucial in maintaining optimal valve performance and preventing any system downtime. The valve seat material selection depends on various factors, such as the fluid or gas being handled, temperature, pressure, valve's design, and the reliability of the industrial valve company.
The selection process requires careful consideration of these factors to ensure that the valve seat material can withstand the operational conditions and prevent any system failures.
In this valve seat material selection guide, we will provide insights into different options available in the market, their properties, pros, and cons.
A valve seat is a ring-shaped component placed in the valve body, which provides a sealing surface for the valve's closure member, ensuring that the valve is tightly closed and prevents fluid or gas leakage. It is typically made from a durable material that can withstand high temperatures, pressures, and corrosive environments. They are used in various types of valves, including industrial ball valves, butterfly valves, gate valves, globe valves, check valves, etc.
The valve seat material is crucial in determining the valve's durability, reliability, and performance, and the selection process requires contacting the valve supplier for careful consideration of different types of materials commonly used for making valve seats.
Virgin PTFE (Polytetrafluoroethylene) is a synthetic fluoropolymer that is known for its excellent chemical resistance, low friction, and high-temperature (260°C) capability. It is non-reactive, non-toxic, and has a low friction coefficient, which makes it suitable for applications where low wear, low friction, and chemical resistance are required.
Virgin PTFE in valve seats can be used in the chemical processing, pharmaceuticals, food and beverage, and semiconductor industries, where their excellent chemical resistance and non-reactivity are required.
Reinforced PTFE is a composite material made by adding fillers or reinforcements to Virgin PTFE to improve its mechanical properties. The addition of fillers enhances the tensile strength, compressive strength, wear resistance, and thermal conductivity of PTFE. The most common types of fillers used in Reinforced PTFE include glass fiber, carbon fiber, and bronze.
Reinforced PTFE valve seats can be used in the chemical processing, oil and gas, and power generation industries, where their enhanced mechanical properties, chemical resistance, and thermal conductivity are required. The type and amount of fillers can affect the properties of the material, so careful selection and testing is required for specific applications.
TFM (tetrafluoroethylene modified with a small amount of perfluoropropyl vinyl ether) is a modified version of PTFE (Polytetrafluoroethylene), with better mechanical properties and thermal stability. The addition of perfluoropropyl vinyl ether to the PTFE molecule creates a more amorphous structure, which increases the flexibility of the polymer chains and enhances its mechanical properties.
TFM valve seats are used in the chemical processing, pharmaceutical, and food and beverage industries, where their excellent chemical resistance, high-temperature capability, and low coefficient of friction are required.
PEEK (Polyether ether ketone) is a high-performance thermoplastic polymer with excellent mechanical, thermal, and chemical properties. It has a high melting point of around 340°C (644°F) and can withstand continuous use at high temperatures up to 250°C (482°F).
PEEK valve seats are used in the aerospace, automotive, and oil and gas industries, where their excellent mechanical properties, high-temperature capability, and chemical resistance are required.
DELRIN is a high-performance thermoplastic polymer with excellent mechanical properties and low friction. It is a type of acetal, also known as polyoxymethylene (POM). DELRIN has a high melting point of around 175°C (347°F) and can withstand continuous use at temperatures up to 100°C (212°F).
DELRIN valve seats are used in the automotive, aerospace, and consumer goods industries, where their excellent mechanical properties, low coefficient of friction, and dimensional stability are required.
Ultra-High Molecular Weight Polyethylene (UHMW PE) is a high-performance thermoplastic polymer with excellent mechanical and chemical properties. It has a high molecular weight, which contributes to its high strength and toughness. UHMW PE has a relatively low melting point of around 130°C (266°F) and can withstand continuous use at temperatures up to 80°C (176°F).
UHMW PE valve seats are used in the chemical processing, food processing, and medical industries, where their excellent mechanical properties, low coefficient of friction, and chemical resistance are required.
Metal is a widely used material for making valve seats due to its excellent mechanical properties, high temperature capability, and good corrosion resistance. Metals commonly used for valve seats include stainless steel, bronze, brass, and titanium, among others.
Metal valve seats are used in the chemical processing, oil and gas, and aerospace industries, where their excellent mechanical properties, high temperature capability, and good corrosion resistance are required.
Source: Istock50-50 stainless filled PTFE is a composite material made by combining PTFE with stainless steel particles. It's often used by a professional butterfly valves manufacturer because of its combination of the PTFE chemical resistance and low friction coefficient with the mechanical properties of the stainless steel.
50-50 stainless filled PTFE valve seats are used in the chemical processing, food processing, and pharmaceutical industries, where their excellent chemical resistance, low coefficient of friction, and good mechanical properties are required.
Cavity filler is a type of valve seat material used in high-pressure gas applications. It is made of a soft, compressible material, typically a fluoropolymer or elastomer that is designed to fill the space between the valve seat and the metal sealing surface of the valve. This helps to prevent gas from leaking through the valve when it is in the closed position.
Cavity filler valve seats are used in high-pressure gas applications, such as natural gas pipelines and gas storage facilities, where gas leakage can have serious safety and environmental consequences.
Viton is a type of fluoropolymer elastomer that is often used as a valve seat material in high-temperature and high-pressure applications. It is a trade name for a group of fluoroelastomers developed by the DuPont company and is known for its excellent chemical resistance, high-temperature resistance, and good compression set resistance.
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Viton valve seats are used in high-temperature and high-pressure applications, such as in the oil and gas, chemical processing, and aerospace industries.
The material used to make the valve seat has a huge part in playing in the sealing functionality of the valve. There are different types of valve seat materials with each of them having their properties and preferred applications. Using a material for an application that's not best for can compromise the performance of the valve.
In this valve seat material selection guide above, we've explained the commonly used materials. However, sometimes they seem to be identical. At Dombor Valve, we will educate you on the distinction between them and provide you with the best valve seat solution needed for your project.
Source: DomborWe only use materials that are safe and eco-friendly to contribute to the sustainability of the environment. And all our materials and products are certified by the CE, ISO, and EA. You can contact us to get started.
In today's guide, I will discuss all essentials of selecting the correct valve seat materials.
Ball valves are essential in allowing to cut or pass the flow and pressure of a piping system. Moreover, they are used in industries such as the petrochemical and pharmaceutical where leakage could represent a terrible consequence for the environment or the product itself. Therefore, the ball valve seat is critical in such situations since it is responsible for sealing the fluid inside and distributing the seating stress uniformly.
In the below picture, we have painted the valve seats in red color so you can identify where is the valve seat:
So, selecting the appropriate ball valve seat materials is vital to guarantee the performance of the valve and the safety of the product and the environment. The most common ball valve seat materials include PTFE, PEEK, and POM.
POM, called Acetal, POM-C, or Delrin, is trademarked by 3M. To select the most appropriate one, there are three main factors to consider:
Fluid compatibility refers to the material being capable of operating in contact with the fluid without having an adverse reaction.
PTFE, also known as Teflon, has very high chemical compatibility, which is why it is commonly used across different applications. Moreover, it is also produced in FDA grade, thus making it compatible with pharmaceutical, food, and drinks products. The only compatibility problem of the PTFE appears when exposed to fluorine or alkalies. We also do not recommend PTFE seats for pressures up to 350 bar.
PEEK is a material with very similar properties to those of the PTFE. Therefore, its fluid compatibility is also similar, including FDA grades. However, it may fail when exposed to sulfuric acid.
Finally, while POM fluid compatibility is extensive and includes radioactive applications, it is essential to highlight that it does not perform well with oxygen flow.
If you want to verify compatibility with the fluid of your application, you can use our compatibility tool here. Our tool allows you to select a material and will tell you how compatible it is with the specific seat.
Another critical aspect of selecting the appropriate ball valve seat materials is the range of temperatures where they can operate. Many materials react differently to temperature changes, and some lose their properties when the temperatures go above or below their normal operational ranges. If a ball valve seat loses its properties or experiences thermal deformation, the sealing power is lost, and the undesired leakage may occur.
We recommend selecting a high-temperature seat or a three-piece ball valve for Socket Weld valves. In that case, the temperature will increase and may melt the valve seats.
When it comes to PTFE, the operational temperature can be in the range of -45°C to 230°C. Now, if your application exceeds these limits, you will be better off using PEEK seats since this material can perform well within the range of -56°C to 315°C, including steam service up to 260°C. Those figures are theoretical since it needs to be added a safety factor.
POM is a more limited material when it comes to temperature. This material can only work at low temperatures within -56 °C to 100°C. However, POM would be an appropriate ball valve seat material for applications where pressure is more critical than temperature, which takes us to the next point.
Temperature ranges with safety factors:
POM PTFE PEEK -30ºC-40ºC-50ºC+100ºC+190ºC+250ºCSimilar to temperature range, pressure range refers to operating pressure values where the ball valve seat material will not suffer deformation or alter its properties. While some materials may be strong enough to withstand high pressures, others may fail at certain levels.
For example, PTFE ball valve seats will have no problems operating at pressures reaching the 350 bar.
You can refer to this table for maximum pressure ranges according to the valve diameter:
Valve Bore SizePOMPTFEPEEKDN6 DN10 DN13 DN20 DN BAR OR MORE350 BAR500 BAR OR MOREDN 32 ' DN40 ' DN BAR OR MORE175 OR 150 BAR APROX.450 BAR OR MOREAs you can see, there are many different aspects to consider. PEEK may be better for some applications because they need valves operating with hot water or steam. For others, the low friction coefficient of POM may be more relevant.
So far, we have only analyzed the maximum working pressure at ambient temperature. Depending on the temperature, the valve pressure is less. But when we arrive at very high or very low temperatures, the pressure that can withstand the valve is different. In the below graph, we see a comparison of the three seats for a 1/2' valve (DN13) working pressure and temperature chart:
Also, there are variations of these materials, like the reinforced version of the PTFE called RPTFE that, with its 15%-25% glass fiber reinforcement, provides an improved lifecycle. Another example would be the TFM, a second-generation PTFE with better stress resistance and recovery and higher pressure capability, elasticity, and resilience. We have recently added TFM as an option for some specific valves.
An Oring or gasket is an elastic ring that prevents the fluid from leaking. This elastomeric material usually is FKM or Viton, NBR or Buna, FFKM or Kalrez, EPDM, etc. The temperature of the o-ring needs to be checked as well since it can melt if the working temperature of the valve is too high.
If you have any other questions, do not doubt contact us. And if you prefer, you can call us; we love to have a little chat with you.
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