Can you make and ship seals the same day?
Yes, using our CNC Instant Seal Manufacturing Machine, we can ship seals in a hurry! An expediting fee is required for same day shipments. For further information on our rapid seal production click here.
How large in diameter can you manufacture?
With our CNC Instant Seal Manufacturing Machine we can make inch sizes from 1/64″ to 60″ and metrics from 1MM to 1500MM.
How do I know what delivery services are available for a product?
EPM offers expedited services based on the customers needs and the materials available.
Can you give me the general characteristics and properties of commonly used seal materials?
ETHYLENE PROPYLENE RUBBER (EPM, EPDM, EPR):
This elastomer is a copolymer of ethylene and propylene and is sometimes compounded with a third monomer (EPT). Good to excellent compression set resistance is obtained by the addition of peroxide cures during vulcanisation. Ethylene propylene materials have excellent resistance to phosphate esters such as Skydrol, Fyrquel, Pydraul, water and steam, acids, alkali, salt solutions, ketones, alcohol’s, glycol’s, and silicone oils and greases. EPDM has very poor resistance to petroleum oils and diester-base lubricants. Ethylene propylene is a close contender to Buna-N and butyl in the important sealing properties, except that it does not have the petroleum oil and fuel resistance of Buna-N, nor the low-gas-permeability quality of butyl.
NITRILE OR BUNA-N RUBBER: More nitrile seals are used than all the other elastomers combined, since nitrile is the most versatile material. Nitriles are a copolymer of acrylonitrile and butadiene. As the acrylonitrile content of nitriles increases, the oil and fuel resistance increases while the low-temperature flexibility decreases. Nitrile-based elastomers are usually specified by military MS and AN O-rings when used in oil and fuel applications, but because nitrile compounds vary widely within such a large overall temperature range, particular attention should be paid to specifying physical properties. Materials can be formulated to perform satisfactorily over the temperature range -22 to +230 degrees F, so it is necessary to make sure that the particular nitrile chosen meets the temperature requirements of the application. The nitrile materials are recommended for general-purpose sealing of alkaline and salt solutions, petroleum oils and fluids, vegetable and diester oils, silicone greases and oils, ethylene glycol-base fluids, alcohol’s, gasoline’s and water. They are not suited for use with strong oxidising agents; chlorinated solvents such as carbon tetrachloride or trichlorethylene, nitrated hydro-carbons such as nitrobenzene or aniline; keytones such as methyl ethyl ketone (MEK) and acetone; and aromatic hydrocarbons. Ozone will will usually attack nitrile materials, but resistance can be greatly improved by the addition of antioxidant compounds.
FLUOROCARBON RUBBER (FPM): Fluorocarbon elastomers have been compounded to meet a wide range of chemical and physical requirements. Fluorocarbons (FPM) seals have been employed where other materials cannot survive severe chemical conditions. The working temperature range of FPM is between -20 and +400 degrees F (-29 and +204 degrees C) and limited temperature spikes of 600 degrees F have been incurred. New compoundings have greatly improved the compression set of fluorocarbon O-ring seals.
SILICONE RUBBER (MVQ): Silicone elastomers are compounded from dimethy silicone polymers, and thus will deteriorate if used with silicone oils and greases. Various additives have extended the functional temperature range of silicone rubber beyond any other elastomer. Flexibility below -76 degrees F (-60 degrees C) and service above 392 degrees F (200 degrees C) for short periods of time have been demonstrated. High production cost have normally limited the use of silicone seals to applications requiring extreme temperature resistance. Production moulding of silicone seals involves high-temperature secondary cure which results in greater than normal shrinkage. The finished O-ring seal is usually undersized when produced in standard moulds. The designer should be aware of this size difference when designing glands for silicone O-rings. Silicone elastomer have poor resistance to keytone solvents such as MEK and acetone, and poor resistance to most petroleum fluids. They have very poor physical properties that make them unattractive for dynamic applications. Silicone seals are recommended for extreme temperature use with ozone, oxygen, high-aniline point oils, and chlorinated diphenyls.
POLYURETHANE (HPU, PU): Polyurethane elastomers are compounds of polyethers and diisocryanates. These materials have excellent physical properties of abrasion resistance and tensile strength, which make them outstanding for dynamic applications. They have excellent resistance to weather, ozone, and oxygen, good resistance to hydrocarbon fuels, petroleum oils, and aliphatic solvents and fair resistance to aromatic hydrocarbons. Acids, keytones, and chlorinated hydrocarbons attack and deteriorate polyurethane. Because polyurethane is available in castable liquids, injection-mouldable pellets and millable gums, it is a very useful material for specialized sealing problems.
Correcting Seal Failures
When in trouble there is a simple process to follow in correcting any type of seal failure.
A. Re-examine your seal selection process.
B. Examine complete system.
C. Carefully examine failed seal for evidence of:
1. Softening or hardening of seal material
2. Dimensional changes in seal
3. Surface tears, scratches, extrusion or other physical damage
4. Obtain sample of system hydraulic fluid.
D. Contact EPM, Inc. to assist in analysis of failure and recommended solution.
SYSTEM CONTAMINATION is usually caused by external elements such as dirt, grit, mud, dust even ice and internal contamination from circulating metal chips, break-down products of fluid, hoses or other degradable system components. As most external contamination enters the system during rod retraction, the proper installation of a rod wiper/scraper is the best solution. Internal contamination is best prevented by a proper filtering of system fluid. Contamination is indicated by scored rod and cylinder bore surfaces, excessive seal wear and leakage.
SPIRAL FAILURE is often the result of a combination of factors such as basic seal geometry, long stroke and/or too soft an elastomer. The classic spiral failure usually is found in a simple O-ring type seal but will sometimes be evident in unsupported lip type seal as well. The use of T-Seals, harder durometer materials, and seals with rectangular cross-sections will usually solve this problem.
CHEMICAL BREAKDOWN of the seal material is most often the result of incorrect material selection in the first place, or subsequent change of system fluid. Misapplication or use of non compatible materials can lead to chemical attack on seal by fluid additives, hydrolysis and oxidation reduction of seal elements. Chemical breakdown can result in loss of seal lip interface, softening of seal durometer, excessive swelling or shrinkage.
IMPROPER INSTALLATION is a major cause of seal failure. The three broad areas to be watched during seal installation are; cleanliness, protecting the seal from nicks and cuts and proper lubrication. Other problem areas are over tightening of the seal gland where there is an adjustable gland follower or folding over a seal lip during installation. The solution to these problems is common sense and taking reasonable care during assembly.
EXTRUSION of the seal element is usually caused by excessive clearances in metal components, high axial loading, high pressure and use of too low a durometer seal material. Extrusion causes a loss in seal volume and stability. The prevention of extrusion usually requires a type of seal with built-in anti-extrusion rings.
HEAT DEGRADATION is to be suspected when the failed seal exhibits a hard, brittle appearance and/or shows a breaking away of parts of the seal lip or body. Heat degradation results in loss of sealing lip effectiveness through excessive compression set and/or loss of seal material. Causes of this condition may be use of incorrect seal material, high dynamic friction, excessive lip loading, no heel clearance and proximity to outside heat source. Correction of heat degradation problems may involve reducing seal lip interference, increasing lubrication, change of seal material. In borderline situations consider all upper temperature limits to be increased by 50 degrees F in dynamic reciprocating seals at the seal interface due to running friction.
SLIP-STICK is an expression of the differential between the static and dynamic coefficient of friction as it relates to start-up of a sliding mechanism. Slip-stick occurs when the seal “hangs-up” in the transition period between static and dynamic modes or there is a variation in the system fluid pressure, or shock loads cause the piston to jump back to the static mode. The most noticeable result of Slip-Stick is erratic or jerky movement of the outer rod. Slip-Stick often creates an audible noise and excessive heat and seal wear can occur.