German FOMET seals FOMET models FOMET prices

FOMET seals are the customary term for general seals, simply referring to lubricating oil seals. They are mechanical components used to seal grease (oil is the most common liquid in transmission systems, and also refers to general liquids), isolating lubricated parts from output parts in transmission components to prevent lubricating oil leakage. Seals used for static sealing and dynamic sealing (generally reciprocating motion) are called oil seals. The representative form of oil seals is the TC oil seal, which is a double-lip oil seal with a self-tightening spring fully covered by rubber; generally, when people refer to oil seals, they often mean this type of tc skeleton oil seal.

FOMET seal types

1) Compression seals: Compression seals, especially O rings, have been widely used in seals. Other types such as X, T, D, square, and triangular shapes are suitable for different applications. Improvements aim to stabilize sealing performance, increase pressure resistance, and reduce friction. They can also be combined with low-friction plastics like PTFE or nylon slide rings and support rings to form composite seals, enhancing pressure resistance and reducing friction. Some manufacturers' products are rated for speeds up to 7.5m/s and sealing pressures of 5.6MPa. 2) Reciprocating lip seals: Reciprocating lip seals, also known as lip gaskets or cups, are widely used for dynamic sealing in hydraulic cylinder reciprocating motions. The pressure-bearing surface is lip-shaped, with a slight interference fit during installation to ensure full contact between the lip edge and the sealing surface. As the cylinder operates, increasing pressure increases contact force and area, improving sealing. During the return stroke, pressure decreases, reducing contact area and friction compared to the working stroke, creating a breathing effect that lubricates the lip. There are many types of reciprocating dynamic seals, commonly including J, L, U, V, and Y types, as well as various composite and combination seals such as bellows, bud, and multi-lip seals. Extrusion must be prevented under high pressure by selecting materials with sufficient tear strength, hardness, and modulus, or by using support rings or reinforced elastomers. Seals used in high-pressure, high-speed, or high-temperature conditions often use composite combination seals. Their common feature is two lips contacting the cylinder wall. A groove in the middle of the sealing area stores media, improving lubrication, reducing lip wear, and ensuring reliable sealing. Lip seals for pneumatic systems require operation without oil lubrication, with specific contact pressure requirements; some integrate dust wipers with the seal. 3) Rotating shaft lip seals: There are no fewer than 200 varieties with similar structures, such as hydrodynamic, internal skeleton, assembled, external skeleton, PTFE-bonded AF type, and dual-modulus return flow type. The advantage of external skeleton assembly is accurate positioning, high concentricity, and good heat dissipation. It remains stable under pressure and vibration, resulting in longer service life and saving rubber material. The dual-modulus return flow type applies wave seal theory, adding a low-modulus, easily deformable material at the sealing contact point to achieve a return flow effect, while reducing product design and mold processing costs. Flexible sealing treatment should be applied at joints between rigid waterproof layers and gable walls, parapet walls, and protruding roof structures.

FOMET seal influencing factors

Hydraulic seals play a crucial role in the integrity of hydraulic and pneumatic systems. If the seals of a hydraulic or pneumatic component are substandard, the component itself cannot be considered a good product. Many factors affect seals. First, pressure is a significant factor influencing seal quality; the magnitude of pressure and the duration of pressure cycles greatly impact seal damage (such as extrusion). Higher pressure amplifies the influence of other factors on seal performance, such as temperature, speed, seal material, clearance between piston and cylinder barrel, and clearance between piston and cylinder head. Another factor is temperature and friction. Describing the maximum and minimum operating temperatures for a seal material is difficult because it results from the combined influence of multiple factors. Operating temperatures for pistons and piston rods differ, requiring distinct selections. Additionally, seal surface roughness, surface characteristics, pressure, media, temperature, seal material, seal type, and motion speed all influence seal performance. Finally, surface treatment is critical; experience shows that the surface characteristics of cylinder pistons and piston rods significantly affect seal life. Surface characteristics are often defined by the surface roughness value RA, which is the arithmetic mean of the absolute deviations of the surface profile from the centerline. However, these values do not fully represent the impact of surface conditions on seals, as different surface shape features can cause varying degrees of seal wear even at the same roughness level.

FOMET seal installation technical requirements

Mechanical seals are high-precision mechanical components, and correct installation and operation significantly impact their service life. We generally follow standards specified by the Ministry of Petrochemical Industry. The technical requirements for pumps installing mechanical seals and their mating parts are as follows: 1) Shaft bending: Maximum not greater than 0.05 mm; 2) Rotor runout: Near the shaft sleeve at the dynamic ring seal circle, not greater than 0.06 mm; 3) Axial shaft movement must not exceed ±0.5 mm; if a shaft sleeve is present, it must not be loose; 4) Coupling alignment error: For gear couplings, not greater than 0.08–0.10 mm (P2008C); for elastic couplings, not greater than 0.05–0.06 mm; (customary practice: end runout<0.05, radial runout<0.10) 5) Concentricity tolerance of the gland (static ring seat) and sealing spigot relative to the shaft centerline is 0.05 mm; perpendicularity tolerance of the face contacting the gasket relative to the centerline is 0.03–0.05 mm. If requirements are not met, the seal chamber must be machined; 6) The ends of the shaft sleeve where the dynamic ring seal is installed, and the ends of the gland (or housing) where the static ring seal is installed, should be chamfered and smoothed. 7) Handle mechanical seals carefully during installation and removal; strictly prohibit using hammers and flat chisels to avoid damaging seal elements. If scale prevents removal, clean thoroughly before disassembly. 8) If mechanical seals are used on both ends of the pump, coordinate during assembly and disassembly to avoid neglecting one side. 9) For operated mechanical seals, if gland loosening causes seal movement, the dynamic and static ring parts must be replaced and not merely retightened for continued use. Loosening changes the original running track of the friction pair, easily compromising the sealing integrity of the contact surfaces.

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