German bihl seals bihl models bihl prices

bihl seals are devices that prevent fluid leakage, consisting of at least one pair of end faces perpendicular to the axis of rotation. These faces remain in contact and slide relative to each other under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism, along with the assistance of auxiliary seals. Mechanical seals where the elastic loading mechanism and auxiliary seal are metal bellows are referred to as metal bellows seals. In light-duty seals, rubber bellows are sometimes used as auxiliary seals; however, since the elastic force of rubber bellows is limited, springs are generally required to supplement the loading force. Mechanical seals are commonly abbreviated as "mech seals".

bihl seal classification

Oil seals are generally classified into single-piece types and assembled types. Assembled types allow free combination of the cage and lip material, and are generally used for special oil seals. Based on sealing function, characteristics, structural type, operating state, and sealing mechanism, oil seals can be divided into various forms with different names. However, by convention, rotating shaft lip seals are called oil seals, while seals for static and dynamic (generally reciprocating) applications are called seals. The representative form of an oil seal is the TC oil seal, which is a double-lip oil seal with a self-tightening spring fully encapsulated in rubber. The term "oil seal" commonly refers to this type of tc caged oil seal.

bihl seal materials

Common materials for oil seals include: Nitrile rubber, Fluoroelastomer, Silicone rubber, Acrylate rubber, Polyurethane, Polytetrafluoroethylene, etc. 1) Nitrile rubber (NBR): It offers good heat and wear resistance, and resistance to various lubricating oils, greases, and oil-gas mixtures. The applicable temperature range is -30~120 degrees Celsius. However, it cannot be used in phosphate ester hydraulic fluids or gear oils containing extreme pressure additives. It performs stably in gasoline and low-aniline-point mineral oils. 2) Polyacrylate rubber (ACM): It has superior oil and heat resistance, wear resistance, ozone resistance, and UV radiation resistance. It is especially resistant to lubricating oils, gear oils, motor oils, engine oils, and petroleum-based hydraulic fluids containing extreme pressure agents. It is suitable for operation in the -30~150 degrees Celsius range. 3) Fluoroelastomer: It offers aging, heat, and oil resistance, and is suitable for almost all lubricating oils, fuel oils, and gasoline. It does not harden easily in oils containing extreme pressure additives. However, it has poor cold resistance and high-temperature wear resistance, and exhibits significant permanent compression set. It is suitable for temperatures from -20~250 degrees Celsius. 4) Silicone rubber: It features outstanding high and low-temperature resistance. It can be used long-term at 150 degrees Celsius without performance change; it can be used continuously at 200 for 10000h. It maintains its unique elasticity, ozone resistance, and weather resistance within the working temperature range of -70~260. 5) Polytetrafluoroethylene: It features outstanding chemical stability, thermal stability, friction reduction, and self-lubrication. Its decomposition temperature is above 400. Therefore, it can operate normally within the temperature range of -200~300 degrees Celsius. Except for free fluorine and alkali metals, it has excellent corrosion resistance to chemicals, solvents, hydroxides, and acids. Nitrile rubber and fluoroelastomer are widely used oil seal materials. The former is low-cost, while the latter offers significant improvements in temperature resistance and sealing performance but is more expensive. It still retains some common disadvantages of ordinary rubber materials, such as poor wear resistance, short service life, and high sensitivity to shaft eccentricity, so leakage phenomena remain relatively common. PTFE oil seals are high-tech products and represent the future direction of oil seal development [2]. When selecting oil seal materials, compatibility with the working medium, adaptability to the working temperature range, and the lip's ability to follow the high-speed rotation of the shaft must be considered. Generally, the lip temperature of an oil seal during operation is 20~50℃ higher than the working medium temperature, which should be noted when selecting materials. The operating range of an oil seal depends on the material used: Nitrile rubber (NBR) is -40~120℃, Acrylate rubber (ACM) is -30~180℃, and Fluoroelastomer (FPM) is -25~300℃.

bihl seal maintenance

1) Control of shaft seal pressure: High shaft seal pressure can cause steam leakage from the shaft seal, leading to water ingress into the oil and deterioration of turbine oil quality. Excessively high shaft seal pressure will trigger the safety valve of the equalizing tank, wasting working fluid and damaging equipment. Low shaft seal pressure may cause a drop in unit vacuum, allowing cold air to enter the shaft seal or even the cylinder, causing cooling of the shaft seal section or inside the cylinder, which seriously threatens equipment safety. 2) Impact of abnormal shaft seal temperature on the unit: When the shaft seal temperature is too high, especially before unit startup, excessive heat causes intense heating of the shaft end gland and rotor gland sections, leading to local stress concentration and deformation. This may alter the clearance between the rotor and cylinder, increase shaft seal steam leakage and differential expansion, and potentially cause serious rubbing between stationary and rotating parts. When the shaft seal temperature is too low, the shaft end gland and rotor gland sections are cooled, also causing local stress concentration, altering the clearance between the cylinder and rotor, increasing shaft end leakage, and reducing differential expansion. Low shaft seal temperature may also cause water carryover in the shaft seal supply steam, leading to water hammer in the supply pipes. In severe cases, this can cause water ingress into the turbine.

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