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Rod Seals
The rod seal is the most critical seal on any type of fluid power equipment preventing leakage of fluid from within the cylinder to the outside. Leakage through the rod seal can reduce equipment performance, and also in extreme cases can cause environmental issues.
HydraPro Bahrain offers a wide range of hydraulic rod seals for both single-acting and double-acting systems. These include a unique profiled NBR energised polyurethane (PU) seal, and a specifically designed three element seal for the mining industry comprising of an O-ring energiser, PU shell and a polyacetal anti-extrusion ring.
Particular attention should be paid to pair the rod seal and the wiper for the best sealing performance. If a less aggressive rod seal is paired with an aggressive wiper, the wiper can scrape off the microscopically thin film of oil that remains on the rod in microscopic surface imperfections during the return stroke, resulting in system leakage.
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Rod Seal Type
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Single Acting Piston Seals
Piston Seals or Piston Rings are used in hydraulic cylinders for fluid sealing and are designed to ensure that pressurised fluid does not leak across the cylinder head as the system pressure pushes the piston down the cylinder bore.
The choice of piston seal is decided by the way in which the cylinder operates. For a cylinder which is exclusively single-acting, capable of sealing dynamic pressure from one side (unidirectional), it is always best to choose the type of seal designed to provide optimum sealing qualities for single-acting functions.
The best sealing capacity of a double-acting cylinder, capable of sealing dynamic pressure from both sides (bidirectional), is achieved by choosing a double-acting seal.
A piston design where two single-acting seals on the piston for a double-acting cylinder are used can easily give rise to a breakdown. The reason is that a very high pressure can be trapped between the seals.
Piston seals, both single and double-acting, can be designed for and used with integrated or separate back-up rings and guide rings.
HydraPro Bahrain offers a wide range of piston seals that provide the ultimate in leakage control. Piston seals are usually manufactured in our high performance polyurethane / rubber / fabric composite or polyester elastomer.
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Double Acting Piston Seals
Piston Seals or Piston Rings are used in hydraulic cylinders for fluid sealing and are designed to ensure that pressurised fluid does not leak across the cylinder head as the system pressure pushes the piston down the cylinder bore.
The choice of piston seal is decided by the way in which the cylinder operates. For a cylinder which is exclusively single-acting, capable of sealing dynamic pressure from one side (unidirectional), it is always best to choose the type of seal designed to provide optimum sealing qualities for single-acting functions.
The best sealing capacity of a double-acting cylinder, capable of sealing dynamic pressure from both sides (bidirectional), is achieved by choosing a double-acting seal.
A piston design where two single-acting seals on the piston for a double-acting cylinder are used can easily give rise to a breakdown. The reason is that a very high pressure can be trapped between the seals.
Piston seals, both single- and double-acting, can be designed for and used with integrated or separate back-up rings and guide rings.
HydraPro Bahrain offers a wide range of piston seals that provide the ultimate in leakage control. Piston seals are usually manufactured in our high performance polyurethane / rubber / fabric composite or polyester elastomer.
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Vee Packs
Vee pack sets are multiple-lip (chevron) seals, usually composed of a male and female adaptor and a group of three or five vee rings, are popular for sealing rods and pistons in medium to heavy duty applications and are compatible with both single and double acting cylinders.
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Wipers
Wipers are installed in the sealing configurations of hydraulic cylinders to prevent contaminants such as dirt, dust and moisture from entering the cylinder as they retract back into the system.
Contamination can cause significant damage to the rod, cylinder wall, seals, and other components, and is one of the primary causes of premature seal and component failure in a fluid power system.
HydraPro Bahrain offer a wide range of hydraulic wipers in High Performance polyurethane, Nitrile and other polyester based materials, along with press-fit metal caged ranges.
The wiper seal is the most undervalued seal type in the hydraulic cylinder in relation to its important function. Particular attention should be drawn to its selection, the surrounding environment and service conditions must also be taken into special consideration.
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Use and Fitting of Seals
Our quality control methods for material and manufacturing processes ensure that all seals leaving our factories are in a condition capable of giving a long and reliable service life.
We have found from many years experience, that premature seal failure can be avoided if the following recommendations are considered at the design manufacturing stage of the cylinder:
- Specify piston and gland bearings which are adequately proportioned to support the cylinder loads.As a result of mounting misalignments and / or the working action of the cylinder, piston and gland bearings will be subjected to side-loading, causing damage to the rod or the tube surface and hence the seal, if the bearings are inadequate.
- Ensure that seals are stored distortion free in a cool, dry and dark place prior to fitting.
- Check that the seal housing is free from damage likely to harm the seal. Remove all sharp edges and burrs from metal parts, paying particular attention to ports, grooves and threads over or through which the seal passes during assembly.
- Clean all seal housing areas, ensuring that all metallic particles and other contaminants have been removed. Check that other surfaces adjacent to the passage of the seal on fitting are also free of dirt, swarf or other contaminants. Check that both static and dynamic housing surface finishes meet specifications.
- Where the difference between a thread diameter over which the seal must pass and the seal diameter is small, use some form of protection over the thread, such as a fitting sleeve made of hard plastic.
- Check that the seal is of the correct type, part number and size, and that the specified material is correct. If there is any doubt regarding the material contact your local sales office.
- Lubricate all seals and metal components liberally with clean operating fluid or a compatible grease prior to assembly. N.B. Silicone grease should not be used in normal hydraulic applications.
- Where seals fitted to sub-assemblies, such as pistons, are awaiting further fitting operations, ensure that the seals are not subjected to any misaligned or localised loading which will cause local deformation. Ensure that sub- assemblies remain clean.
- The use of metal levers is not recommended but should they be used it is imperative that they are completely smooth and free from nicks and burrs. When using them ensure that the metal surfaces adjacent to the seal are not damaged.
- Flush the hydraulic system thoroughly before connecting the cylinder to it.
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Complete sealing solution
HydraPro Bahrain is a distributor of fluid power hydraulic and pneumatic seals, wiper seals, o-rings, rod and piston seals, bearings and other custom high-performance rubber and plastic parts.
HydraPro Bahrain is at the cutting edge of fluid power technology, manufacturing a wide range of rod / gland, piston, and static seals, as well as support and bearing components, for technically challenging applications, from a wide range of materials which include Polytetra fluoroethylene (PTFE), Polyurethane, nitrile rubbers (NBR) and Fluoro-elastomers.