In today’s guide, I will discuss all essentials of selecting the correct valve seat materials.
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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 DN25500 BAR OR MORE350 BAR500 BAR OR MOREDN 32 – DN40 – DN50450 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.
PEEK vs PTFE: What are the differences?
PEEK valve seats vs PTFE valve seats
In the current market, PTFE vs PEEK has been holding a very high position of the material value and material performance compared to many other plastics. Currently, both PTFE and PEEK have specific applications corresponding to their properties, but there are still concerns about which one is better for certain applications. To clarify this, below is an analysis of the concepts, technical data, properties and applications of PEEK vs PTFE to help you understand a more realistic comparison of these two materials.
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PEEK, also known as Polyetheretherketone, belongs to the group of high performance semi-crystalline thermoplastics. This is a colorless plastic widely used in many technical applications. PEEK has a modulus of 3.6 GPa and possesses a tensile strength of about 90 - 100 MPa. PEEK melts at about 343 °C (662 °F) and has a glass transition temperature of about 143 °C (289 °F). Some types have useful operating temperatures up to 250 °C (482 °F). From here it can be seen that PEEK plastic has a very wide temperature range. Several methods such as injection molding, extrusion or compression molding are often used to shape PEEK plastic. The crystallinity of PEEK and their mechanical properties can be influenced by processing conditions during molding. In terms of properties, PEEK plastic has high mechanical and chemical durability. Evidence can include its ability to be sustainable in non-halogenated environments, strong acids as well as some halogenated compounds and aliphatic hydrocarbons at high temperatures. Additionally, it can completely dissolve sulfuric acid at room temperature. Besides, PEEK plastic also exhibits light weight, flexibility, and low moisture absorption.
PEEK plastic has a chemical durability
Thanks to the properties just mentioned, PEEK plastic is often used to produce piston parts, machinery valves, insulated cables, pumps, etc. PEEK plastic is one of the few plastics that is compatible with many applications. extremely high vacuum. The aerospace, automotive and chemical processing industries have also become fond of PEEK plastic thanks to this property.
Read more: PEEK plastic: Definition and Application
Just like PEEK, PTFE plastic is also a thermoplastic. We may know PTFE by other names such as PolyTetraFluoroEthylene, teflon, fluoropolymer. This is a polymerization of tetrafluoroethylene formed by a chemical reaction that combines particles into large, repeating molecular groups. Tetrafluoroethylene (C2F4), is made by heating chlorodifluoromethane (CHClF2) between 600–700 °C (1,100–1,300 °F). Chlorodifluoromethane is obtained in turn by reacting hydrogen fluoride (HF) with chloroform (CHCl3 ). Tetrafluoroethylene monomers (small, single-unit molecules) are suspended or emulsified in water and then polymerized (bonded into giant, multi-unit molecules) under high pressure in the presence of free radical initiator. The polymer consists of a chain of carbon atoms with two fluorine atoms bonded to each carbon: where the carbon chain is surrounded by fluorine atoms that act as a protective shell. PTFE plastic has quite impressive heat resistance with a very high melting point of up to about 327 ° C. At temperatures below 260°C, PTFE can be used continuously without deterioration.
PTFE is very durable
Some outstanding properties of PTFE include resistance to most corrosive substances, water resistance, extremely low friction coefficient, non-stickiness, and high flexibility. For PTFE, degradation in air by radiation attacks begins to show at a dose of 0.02 Mrad. Applications for manufacturing heat-resistant machinery, machinery in harsh environments, chemical containers and also used in some cooking utensils thanks to its non-stick properties.
Read more: All You Need to Know About PTFE
PEEK plastic bars
PTFE plastic bars
PEEK plastic has high heat resistance, flexibility, durability
In addition, PEEK plastic also exhibits advantages such as resistance to heat radiation, less flammability, less toxic gases, and less aging due to heat.
PTFE has very high chemical resistance
Besides, PTFE plastic also has good resistance to UV radiation, oxidation, adhesion and water resistance.
Some of PEEK applications
Manufacturers choose PEEK for the above applications thanks to its ability to withstand high pressure in harsh environments and its super durability.
Some of PTFE applications
Petrochemical factory
Thanks to its outstanding durability, PTFE is used in a variety of life applications and technical applications.
In general, in terms of the properties of PTFE vs PEEK, these two plastics both show superior properties compared to other plastics. Although they have similar properties, PTFE vs PEEK have quite different applications. Choosing the right material between PTFE vs PEEK for your product will help maximize product performance as well as optimize investment costs. Visit EuroPlas today to access a wealth of useful articles and data on choosing the right materials for your project!
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