• rth

How to select the valve soft seat/ seal material?

Service life is affected by all of the following factors: -size, pressure, temperature,degree of pressure fluctuation and thermal fluctuation,type of media, cycling frequency, velocity of media & speed of valve operation.

The following seat & seal materials can be used in various valves such as ball, plug, butterfly, gate,check valves etc.

The most common material for the ball valve seat insert ring material will be

PTFE,RPTFE,PEEK,DEVLON/NYLON,PPL according to different pressure,size and working conditions.

The most common material for the ball valve soft sealing material will be


To list a few main material characteristic:

BUNA-N (HYCAR or Nitrile) - Temperature range is -18 to 100℃ maximum. Buna-N is a general-purpose polymer which has good resistance to oil,water, solvents and hydraulic fluids. It also displays good compression,abrasion resistance,and tensile strength.This material performs extremely well in process areas where paraffin base materials, fatty acids, oils, alcohols or glycerins are present, since it is totally unaffected. It should not be used around high polar solvents (acetones, ketones), chlorinated hydrocarbons, ozone or nitro hydrocarbons. Hycar is black in colour and should not be used where discolouration cannot be tolerated. It is regarded as a comparable replacement neoprene. Major differences are: Buna-N has a higher temperature limit; neoprene is more resistant to oils.

EPDM - Temperature rating is from -29℃ to 120℃. EPDM is a polyester elastomer made from ethylene-propylene diene monomer. EPDM has good abrasion and tear resistance and offers excellent chemical resistance to a variety of acids and alkalines. It is susceptible to attacks by oils and is not recommended for applications involving petroleum oils, strong acids, or strong alkalines. EPDM should not be used on compressed air lines. It has exceptionally good weather aging and ozone resistance.  . It is fairly good for ketones and alcohols.

PTFE (TFE of Teflon) - PTFE is the most chemically resistant of all plastics. It also has excellent thermal and electrical insulation properties.PTFE’s mechanical properties are low compared to other engineering plastics,but its properties remain at useful levels over a great temperature range (-100℃ to 200℃, depending on brand and application).

RTFE (Reinforced TFE/RPTFE) - Typical temperature range is -60℃ to 232℃. RPTFE/RTFE is compounded with a selected percentage of fibre glass filler to improve strength and resistance to abrasive wear,cold flow,and permeation in molded seats.Reinforcement permits application at higher pressure and temperature than unfilled TFE. RTFE should not be used in applications that attack glass,such as hydrofluoric acid and hot strong caustics.

CARBON FILLED TFE - Temperature range is -50℃ to 260℃. Carbon filled TFE is an excellent seat material for steam applications as well as high efficiency oil-based thermal fluids. Fillers including graphite enable this seat material to have a better cycle life than other filled or reinforced TFE seats. Chemical resistance is equal to other TFE seats.

TFM1600-TFM1600 is a modified version of PTFE that maintains the exceptional chemical and heat resistance properties of PTFE, but has a significantly lower melt viscosity.The result is reduced cold flow porosity,permeability and void content.Surfaces are smoother and reduce torques.The theoretical service range for TFM1600 is -200℃ to 260℃.

TFM1600+20%GF -TFM1600+20% GF is a fibre glass reinforced version of TFM1600. Similar to RTFE,but with the benefit of TFM1600,the glass filled version provides greater abrasion resistance and improves stability at higher pressures.

TFM4215 - TFM4215 is an elector graphitized carbon filled TFM material.The added carbon improves stability for higher pressure and temperature combinations.

VITON(Fluorocarbon, FKM, or FPM)- Temperature rating is from-29℃ to 149℃. Fluorocarbon elastomer are inherently compatible with a broad spectrum of chemicals. Because of this extensive chemical compatibility which spans considerable concentration and temperature ranges, fluorocarbon elastomer have gained wide acceptance as a material of construction for knife gate valve seats.Fluorocarbon can be used in most applications involving mineral acids, salt solutions,chlorinated hydrocarbons and petroleum oils. It is particularly good in hydrocarbon service. Colour is gray (black) or red and may be used on bleached paper lines.Fluorocarbon(VITON)is not suitable for steam or hot water service,however, in o-ring form it can be acceptable for hydrocarbon lines mixed with hot water depending on the type/brand. For seat materials FKM can offer more resistance to hot water-consult manufacturer.

PEEK-Polyetheretherketone-high pressure semi-rigid elastomer.Best suited for high pressure and temperature service. Also offers very good corrosion resistance.Temperature rating -56.6℃ to 288℃.

DELRIN/POM-Special Delrin seats offered for higher pressure and lower temperature service.Can be used in high pressure air, oil and other gas media but are not suited for strong oxidizing.Temperature rating-50℃ to 100℃.

NYLON/DEVLON-Nylon (polyamide) seats are offered for higher pressure and lower temperature service. They can be used in high temperature air,oil and other gas media but are not suited for strong oxidizing. Temperature rating -100℃ to 150℃. Devlon has the characteristics of long-term bottom water absorption, strong pressure resistance and good flame retardancy. Devlon is widely used in oil and natural gas pipelines abroad for the trunnion ball valve class 600~1500lbs.

Edited by News team :sales@ql-ballvalve.com  www.ql-ballvalve.com

China top listed factory specialized in manufacturing ball valves !

Post time: Oct-26-2022