WHAT IS A SOFT SEAL?
Soft packing, also known as braided packing, is a material that physically fills the gap between the shaft and the body. The braid wrapped around the shaft has a rope-like appearance.
These packings vary depending on the area of use, and selections are made according to the fluid, pressure, and temperature in the area.
Generally speaking, soft packing consists of thread and lubricant. The performance of these two materials affects the durability of the packing. The purpose of packing is to prevent the substance pumped by the pump from leaking out between the pump body and the rotating shaft. Soft packing is also used to prevent air from being sucked in from outside.
Another feature of soft packing is that it is conductive, allowing heat generated by friction to be transferred to the body. In some applications, packing fluid is used with soft packing to cool the shaft's friction-generated heat.
Types of Soft Seal
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Graphite Braid: This packing, produced by specially braiding high-quality PTFE yarns impregnated with graphite, is ideal for general-purpose use in all types of pumps in the industry. Thanks to graphite's natural lubricating properties, it has a low friction coefficient. Its main applications include a wide range of chemicals, from petroleum and its derivatives to synthetic oils, acids and bases, solvents, water, steam, and dry air, providing long-lasting performance with superior resistance.
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Pure Carbon: A pure carbon fiber packing made from pure carbon fiber strands, impregnated with PTFE lubricant and woven in an interlock pattern. The lubricant used in its production minimizes friction. It is used in abrasive environments containing acidic caustic chemicals, in mixers, autoclaves, and pulp pumps. Outside of these sectors, the use of gaskets is also quite common in the steel industry in water pumps and hot and cold water pumps.
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PTFE Fiber Mesh: Manufactured with fiber mesh and lubricant. Woven using the interlock horizontal weaving method, it offers maximum tensile strength. It provides safe use in many applications, particularly in high temperatures and with highly corrosive chemicals. Its white color prevents color contamination. It can be used in applications involving fuels, oils, all solvents, monomers, and wastewater, among others.
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Graflex: A pure graphite packing with a low friction coefficient, suitable for use in both pumps and valves with a long service life. It operates with low, and in some applications, zero leakage. Due to the extremely low friction coefficient of the graphite material, it minimizes wear on the shaft.
Applications of Soft Seal
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Chemical reactor Mixer: Used to ensure leak-proofing in rotating equipment.
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Petrochemical Plants: Used in systems that work with acids, bases, solvents, and petroleum derivatives.
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Food and Pharmaceutical Industry: Used in lines requiring chemical resistance and hygienic leak-proofing.
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Kâğıt ve Tekstil Endüstrisi: Nemli ve kimyasal ortamlarda döner ekipmanlarda kullanılır.
Temperature and Pressure Resistance of Soft Packing
Temperature and pressure resistance vary depending on the material used. PTFE, graphite, or aramid-based types generally operate safely at pressures up to 20 bar within a temperature range of -100°C to +280°C. With the right selection, they provide high resistance and long-lasting sealing.
Writer:
Professor Doctor Mustafa Yaşar
Industrial Design Engineer
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