German SCHUNK seals, SCHUNK models, SCHUNK prices

SCHUNK seals are typical representatives of oil seals; the term "oil seal" generally refers to skeleton oil seals. The function of an oil seal is generally to isolate components requiring lubrication within transmission parts from the external environment, preventing lubricating oil leakage. The skeleton acts like reinforcing steel in concrete components, providing reinforcement and enabling the oil seal to maintain its shape and tension. Based on structural form, they can be divided into single-lip skeleton oil seals and double-lip skeleton oil seals. The secondary lip of a double-lip skeleton oil seal serves a dust-proof function, preventing external dust, impurities, etc., from entering the machine interior. Based on skeleton type, they can be divided into internally covered skeleton oil seals, externally exposed skeleton oil seals, and assembled oil seals. Based on operating conditions, they can be divided into rotating skeleton oil seals and reciprocating skeleton oil seals. Used in locations such as gasoline engine crankshafts, diesel engine crankshafts, gearboxes, differentials, shock absorbers, engines, and axles.

SCHUNK seal principle

A mechanical seal is a shaft sealing device that achieves leak prevention by keeping one or several pairs of end faces, which slide relative to each other perpendicular to the axis, in contact under the action of fluid pressure and the elastic force (or magnetic force) of a compensation mechanism, supplemented by auxiliary seals. Common mechanical seal structures consist of components such as a stationary ring (static ring), rotating ring (dynamic ring), elastic element spring seat, set screws, rotating ring auxiliary sealing rings, and stationary ring auxiliary sealing rings. Anti-rotation pins are fixed to the pressure cover to prevent the stationary ring from rotating. The rotating ring and stationary ring can also be referred to as compensation rings or non-compensation rings, depending on whether they possess axial compensation capability.

SCHUNK seal system composition

1) Seal chamber: In the past, seal chambers housing mechanical seals were stuffing boxes designed for soft packing seals. They are unsuitable for housing mechanical seals, not only because the dimensions are too small and the clearances too narrow, but also because the simple cylindrical shape is inappropriate. Standards for enlarged mechanical seal chambers have been established abroad. In addition, companies such as Durametallic in the US and the Fluid Sealing Association (formerly British Fluid Sealing Group) are studying rational mechanical seal chamber designs. Their shapes should not only facilitate fluid flow and heat dissipation but also aid in the removal of solid particles, creating a favorable environment for the seal. 2) Volatile organic compound (VOC) emission control system: In the past, attention was focused only on eliminating visible fluid leaks, neglecting the control of invisible volatile emissions. This resulted in environmental pollution and posed risks to equipment and personnel. Organizations abroad, such as the Sealing Technology Committee of the Society of Tribologists and Lubrication Engineers (STLE) in the US, have established guidelines for controlling volatile emissions in rotating machinery, compressors, and screw systems with mechanical seals, including SP-30 (1994), SP-32 (1990), and SP-33 (1991). SP-30 is implemented in three stages. It clearly defines barrier fluids and buffer fluids, clarifying erroneous and confusing concepts. A barrier fluid is a fluid introduced between dual seals to completely block process fluid from leaking into the surrounding environment. The pressure of the barrier fluid is always higher than the pressure of the sealed process fluid. A buffer fluid is a fluid used between dual seals as a lubricant or buffer; the buffer fluid pressure is always lower than the pressure of the sealed process fluid. 3) Auxiliary system integration: Mechanical seal auxiliary systems require integration of cooling, heating, flushing, and other systems. Pump circulation needs optimization, and condition monitoring systems are being studied and resolved. Auxiliary system integration is specified in the API-682 standard. 4) Gas barrier seal system: In the past, liquid-blocking-liquid or liquid-blocking-gas configurations were common in barrier seal systems. To simplify bulky barrier liquid systems, barrier gases are now used to block liquids or gases. Gas barrier seal systems may employ spiral groove gas seals with barrier gas, floating bushings with barrier gas, etc., to seal against gases and liquids.

SCHUNK seal specifications and applications

1) Standard single-lip type: Generally used for sealing mineral oil, water, and other media on high- and low-speed rotating shafts and in reciprocating motion. Standard oil seals are used in environments with relatively little dust and impurities, resistant to media pressure<0.05MPa, maximum linear speed 15m/s, reciprocating speed<0.1m/s. 2) Standard double-lip type: In addition to the usage characteristics of the aforementioned S type oil seals, it also provides dust protection. Standard oil seals with a dust lip can prevent dust ingress, resistant to media pressure<0.05MPa, linear speed ≤ 15m/s. 3) Springless type: Springless single-lip internally covered skeleton rubber oil seal. Generally suitable for low-speed conditions where the sealing medium is lubricating grease. Linear speed ≤ 6m/s. 4) External skeleton single-lip type: Single-lip externally exposed skeleton rubber oil seal with spring. Features a thin waist, good conformity, and good rigidity. Standard oil seals are used in environments with relatively little dust and impurities, resistant to media pressure<0.05MPa. For cases where rotational axis linear speed ≤ 15m/s. 5) External skeleton double-lip type: Double-lip externally exposed skeleton rubber oil seal with secondary lip. Features a thin waist, good conformity, high rigidity, and good concentricity. Standard oil seals with a dust lip can prevent dust ingress, resistant to media pressure<0.05MPa. Rotational speed ≤ 15m/s. 6) Assembled single-lip type: External skeleton oil seal formed by assembling inner and outer skeletons with rolled edges. Features high installation precision, fast heat dissipation, and heavy-load characteristics. Suitable for heavy-load conditions under high temperature and high speed. Media pressure ≤ 0.05MPa, maximum linear speed ≤ 15m/s. 7) Unidirectional return flow type (right-hand, left-hand): Angled ribs are manufactured on the air side of the lip. Utilizing hydrodynamic principles, it generates a unidirectional pumping action with a return flow effect. Related to the shaft's direction of rotation. Due to the return flow effect, radial force is lower than that of standard oil seals, reducing wear and heat generation, and extending service life. Suitable for media pressure<0.05MPa, rotational speed ≤ 20m/s. 8) Pressure-resistant type: Short lip and short, thick waist provide pressure resistance. Operating pressure ≤ 3MPa. Suitable for applications with media pressure ≤ 3MPa. Applicable as shaft end oil seals for high-pressure pumps. Under normal conditions, the PV value ≤ 8. Rotational axis linear speed ≤ 15m/s.

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