German PIMATIC seals PIMATIC models PIMATIC prices

PIMATIC seals are materials or components that prevent leakage of fluids or solid particles from adjacent mating surfaces and prevent external contaminants such as dust and moisture from entering machinery. The recommended storage temperature for seals is below 30 °C to avoid high-temperature aging. Seals are classified into static seals and dynamic seals. Their main function is to prevent leakage of fluids or solid particles from adjacent mating surfaces and to prevent external contaminants such as dust and moisture from entering machinery. Static sealing refers to the tight closure of sealed chambers and containers, used for sealing letters and wills with stamps.

PIMATIC seal principles

Mechanical seals are shaft sealing devices that achieve leak prevention by keeping one or more 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 the compensation mechanism, supplemented by auxiliary seals. Common mechanical seal structures consist of a stationary ring (static ring), a rotating ring (dynamic ring), elastic elements such as spring seats, set screws, auxiliary O-rings for the rotating ring, and auxiliary O-rings for the stationary ring. Anti-rotation pins are fixed to the gland to prevent the stationary ring from rotating. Depending on whether they have axial compensation capability, the rotating and stationary rings are often referred to as compensation rings or non-compensation rings.

PIMATIC seal system composition

1) Seal chamber: In the past, seal chambers housing mechanical seals were designed as stuffing boxes for soft packing seals. They are unsuitable for mechanical seals, not only because they are too small and have narrow clearances, but also because their simple cylindrical shape is inappropriate. International standards for enlarged mechanical seal chambers have been established. Furthermore, companies such as Durametallic in the US and the Fluid Engineering Study Group in the UK are researching rational mechanical seal chamber designs. These designs should facilitate fluid flow and heat dissipation, as well as the removal of solid particles, creating a favorable environment for the seal. 2) Volatile organic compound (VOC) emission control system: Previously, attention was focused only on eliminating visible fluid leaks, ignoring the control of invisible VOC emissions, which leads to environmental pollution and poses risks to equipment and personnel. Organizations such as the Sealing Technology Committee of the Society of Tribologists and Lubrication Engineers (STLE) in the US have issued 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 misconceptions. A barrier fluid is 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 that of the sealed process fluid. A buffer fluid serves as a lubricant or cushioning agent between dual seals, and its pressure is always lower than that of the sealed process fluid. 3) Auxiliary system integration: Mechanical seal auxiliary systems require integration of cooling, heating, and flushing 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 block gases and liquids.

PIMATIC seal maintenance

1) Control of shaft seal pressure: High shaft seal pressure can cause steam leakage at the shaft seal, leading to water ingress into the oil and deterioration of turbine oil quality. Excessively high shaft seal pressure may trigger the safety valve of the equalizing pressure box, 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 at 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 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 steam leakage, and reducing differential expansion. Low shaft seal temperature may also result in water carryover in the shaft seal supply steam, causing water hammer in the supply pipes. In severe cases, this can lead to water ingress into the turbine.

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