Sep. 09, 2024
Agriculture
30-day refund/replacement
This item can be returned in its original condition for a full refund or replacement within 30 days of receipt. You may receive a partial or no refund on used, damaged or materially different returns.
This type of oil seal is mainly suitable for pressure parts, and belongs to pressure type rotary seals. The lip area of the TCV oil seal is a pressured area, which is reduced due to the improved internal structure of the oil seal, while maintaining a certain strength. It is mainly used for small shaft diameter and medium pressure (up to 0.3MPa).
One of the arguments often used against hydraulic systems isthat dreaded word, leakage. But with proper sealing, leakage won&#;tbe a problem with your system. Sealing is a vital factor in the properfunction of hydraulic applications. Leakage from the cylinder oracross the piston, along with the ingress of unwanted contaminants,can not only decrease the lifespan of the components, but it willaffect the efficiency of the entire application.
Proper material choices will be determined by the seal&#;s environment. Different types of chemicals react differently to different fluids, while some materials have higher pressure and temperature limits. They also must be able to withstand extrusion, so materials are very application-specific.
Polyurethane is an organic material whose chemical composition is characterized by a large number of urethane groups. Urethanes belong to the thermoplastic elastomers (TPE) family and close the gap between thermoplastic and elastomeric materials regarding hardness, deforming behavior and consistency. Within certain temperature limits, polyurethane possesses the elastic characteristics of rubber combined with the advantages of a rigid plastic.
The composition of the material is determined by three components: polyol, diisocyanate and a chain extender. The type and amount of these materials used, and the reaction conditions, are decisive in determining the properties of the resulting polyurethane material. In general, polyurethanes possess the following properties:
&#; high mechanical, tensile strength
&#; good abrasion resistance
&#; modulus of elasticity is variable
&#; wide range of hardness values, while retaining good elasticity
&#; good resistance to ozone and oxygen
&#; outstanding resistance to abrasion and tear
Temperature range for use: &#;30 to 80° C; high performance types (compounds) up to 110° C in mineral oils (long-term exposure temperature).
IMAGE COURTESY OF MFP SEALS
NBR is a polymer of butadiene and acrylonitrile. The acrylonitrile (ACN) component affects the following properties of the NBR:
&#; elasticity
&#; cold flexibility
&#; gas permeability
&#; compression set
&#; swelling resistance in mineral oils, greases and fuels
An NBR material with low ACN content has very good cold flexibility (down to approximately &#;45° C) and moderate resistance to oil and fuel. In contrast, a material with very high ACN content with optimum resistance to oil and fuels, may have a cold temperature flexibility only down to &#;3° C. With rising ACN content, the elasticity and the gas permeability decrease and the compression set becomes worse.
NBR provides:
&#; good resistance to swelling in aliphatic hydrocarbons; greases; fire retardant hydraulic fluids of Groups HFA, HFB and HFC
&#; good resistance to hot water at temperatures up to 100° C (sanitary fittings), inorganic acids and bases at concentrations, and temperatures which are not too high
&#; high swell in aromatic hydrocarbons, chlorinated hydrocarbons, flame retardant hydraulic fluids of the Group HFD, esters
Temperature range for use (depending on the composition of the blend): &#;40 to 100° C and for short periods up to 130° C (the material hardens at higher temperatures). For special blends, the cold flexibility extends down to &#;55° C.
Copolymers, terpolymers or tetrapolymers with various compositions and with fluorine contents from 65 to 71%, which have varying resistance to surrounding media and varying cold flexibility. FKM provides:
&#; tough resistance to high heat
&#; excellent resistance to oil, hydraulic fluid and hydrocarbon solvents
&#; good flame retardance
&#; low permeability to gases
&#; high swell in polar solvents, ketones and fire-retardant hydraulic fluids (i.e. Skydrol type)
Newly developed materials (cross-lined by peroxides) have good resistance to media, which can only be tolerated to a small extent, if at all, by conventional FKM.
Temperature range for use: about &#;20 to 200° C (for short periods to 230° C). Special grades: &#;50° to 200° C.
PTFE is a polymer of tetrafluoroethylene. This non-elastic material is characterized by:
&#; slippery surface that repels most media n
&#; on-toxic at working temperatures up to 200° C
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&#; low coefficient of friction against most opposing surfaces made of other materials; stiction and friction are almost the same
&#; excellent electrical insulating properties (almost independent of frequency, temperature and weathering effects)
&#; chemical resistance that exceeds that of all other thermoplastics and elastomers
&#; liquid alkali metals and a few fluorine compounds attack PTFE at higher temperatures
The temperature tolerance is between &#;200° and 260° C; PTFE has some elasticity even at extremely low temperatures; therefore it is used in many extreme cold temperature applications. Most hydraulic applications require the use of a spring or elastomeric component to energize a lip seal configuration because of the low elasticity and tendency to cold flow over time.
IMAGE COURTESY OF APPLE RUBBER
Following is a list of some of the most common seal designs used in fluid power applications.
&#; provide sealing of the piston and barrel, critical to the function of the cylinder
&#; most often a lip-seal design, but can also be O-rings, T-seals, and so on
&#; must provide efficient sealing, but also reasonably low friction
&#; made from various seal materials, depending on application
&#; require system pressure to effectively activate the lip seal
&#; provide aggressive wiping force
&#; prevent mud, water, dirt and other contamination rom entering the system
&#; allow lubricating oil film to return to system on inward stroke
&#; protect main sealing elements, thus increasing life of seals
&#; often made from polyurethane, which offers high abrasion resistance
&#; often used as a linkage pin grease seal
&#; prevent system fluid from escaping to atmosphere
&#; must provide sealing function at low and high pressure
&#; require excellent extrusion and wear resistance
&#; should provide good pump-back capability for lubricating oil film
&#; often must withstand up to 6,000 psi
IMAGE COURTESY OF TRELLEBORG SEAL SOLUTIONS
&#; must withstand high pressure exposure
&#; protect the rod seal against pressure spikes
&#; feature a pressure-relieving capability that prevents pressure build-up between seals
&#; increase rod seal life
&#; allow for wider extrusion gaps
&#; require high wear resistance
&#; prevent contact between metal parts in the cylinder
&#; center rod and piston from housing elements
&#; increase seal life
&#; most commonly used in static applications and radial or axial deformation to maintain sealing contact force
&#; double-acting, so seal on both sides of a component
&#; can be used as energizing elects or as primary seals
&#; self-acting, so do not require additional system pressure or speed to create the seal
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