Guide to use different types of sealing gaskets

Selection of Sealing Gaskets (1) Natural rubber sheets provide a good seal for water, seawater, air, inert gases, alkalis, and aqueous salt solutions but are not resistant to mineral oils or non-polar solvents. They should not be used beyond 90°C for long-term applications, though they perform excellently in colder environments down to -60°C. Nitrile rubber is ideal for petroleum-based products like oil, lubricants, and fuel. Its optimal operating temperature ranges from 120°C, and it can handle temperatures up to 150°C in hot oil, though its lower limit is around -10°C to -20°C. Neoprene rubber is well-suited for seawater, weak acids, bases, and salt solutions. It offers excellent resistance to ozone and oxidation and performs better than most standard rubbers but falls short of nitrile rubber. It's effective in temperatures up to 90°C, with an upper limit of 130°C, and works in temperatures as low as -30°C to -50°C. Fluoroelastomers come in many varieties and offer superior resistance to acids, oxidants, oils, and solvents. They can be used across nearly all acid media and certain oils and solvents, with a long-term usage temperature of up to 200°C. Rubber sheets used as gaskets are commonly found in frequently dismantled pipe systems or manholes and handholes, with pressures not exceeding 1.568 MPa. Due to their softness and excellent conformability, they seal effectively with minimal preload. However, they are prone to extrusion when the gasket is thick or too soft under high pressure. In organic solvents like benzene, ketones, and ethers, rubber sheets tend to swell, become sticky, and lose their sealing properties. Swelling over 30% makes them unsuitable for use. Under low pressure (below 0.6 MPa) and vacuum conditions, rubber pads work best. For instance, fluoroelastomers are ideal for vacuum containers with degrees up to 1.3×10⁻⁷ Pa, requiring baking and evacuation when used in ultra-high vacuums. Asbestos rubber sheets are cost-effective and user-friendly, yet they suffer from tiny porous gaps that cannot be fully sealed even with rubber and filler additives. This makes them unsuitable for highly polluted media, regardless of pressure or temperature. Over time, in high-temperature oil environments, rubber and filler carbonization weakens the material, leading to leaks and degradation. Additionally, these gaskets may bond to flange surfaces at high temperatures, complicating replacements. (2) Synthetic fiber rubber sheets are eco-friendly, heat-resistant, and pressure-resistant with broad chemical resistance. Bode’s synthetic fiber sheets can withstand up to 120 bar and temperatures ranging from -200°C to 800°C. Sealing performance can be tailored for specific conditions, making it a popular choice in the sealing market. (3) Polytetrafluoroethylene (PTFE) experiences cold flow and creep under pressure and high temperatures, so it’s typically used in low-pressure, medium-temperature applications involving strong corrosives or where contamination is unacceptable, such as in strong acids, bases, and pharmaceuticals. Its safe operating temperature is 150°C with a pressure limit below 1 MPa. While filled PTFE has higher strength, its operating temperature remains below 200°C, with reduced corrosion resistance. Maximum pressure for PTFE gaskets rarely exceeds 2 MPa. (4) Asbestos resin plates and non-asbestos impregnated gaskets are commonly used in acidic media for pipelines, pumps, valves, and flanges. Operating temperature is 80°C, with pressure below 0.6 MPa. (5) Metal-clad asbestos gaskets involve coating an asbestos board or rubber sheet with a thin metal layer to prevent direct contact with the medium, thus preserving strength and preventing leaks. These gaskets can operate at temperatures up to 450°C (some up to 600–700°C) and pressures up to 4 MPa. Increasing the pressure risks cross-leakage and core extrusion. Metal-clad gaskets require significant bolt tightening forces. Even at pressures below 2.45 MPa, flanges below PG 25 kg cannot be used, as they lack sufficient rigidity, leading to deformation and failure. Replacing the core material with elastic synthetic rubber reduces the tightening force. However, this isn’t true since the force is absorbed by the softened core, leaving insufficient force for proper sealing. In chloride-rich or acidic media, overlaps between stainless steel and iron pads may lead to crevice corrosion. (6) Metal flat, corrugated, and toothed gaskets are typically used in medium-to-high-pressure valves, pipes, and smaller-diameter flanged equipment. The operating pressure depends on temperature: flat and corrugated gaskets can handle 1.568–31.36 MPa and 1.568–3.92 MPa, respectively. Material selection depends on the medium and temperature. (7) Octagonal and elliptical gaskets excel in trapezoidal groove flanges and elliptical seals (known as “oil rings” in refining). Octagonal gaskets achieve surface contact, while elliptical ones rely on line contact. Elliptical gaskets seal well under low tightening forces but require two passes, whereas octagonal gaskets seal effectively after a single tightening. Both require high bolt forces and are best suited for high-pressure, low-temperature applications where flange levels exceed PG 25 kg. --- This comprehensive guide provides insight into selecting the right sealing gaskets based on application requirements and environmental conditions.

Aluminium Casement Windows

aluminium casement windows,aluminum casement windows,aluminum casement,casement window aluminum

SMIRO DOORS AND WINDOWS CO., LTD , https://www.smirowindows.com