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Selection and Scope of Eight (8) Types of Flange Gaskets (V)

06 Metal Spiral Wound Gasket

The metal spiral wound gasket ingeniously utilizes the heat resistance, resilience and strength of metal and the flexibility of non-metallic materials, so the sealing performance is good, and the performance of stainless steel spiral wound flexible graphite gasket is the best. Its pre-tightening specific pressure is smaller than asbestos winding pad, and there is no defect of asbestos fiber pore leakage.  In oil media, 0Cr13 is mostly used for metal strip, while 1Cr18Ni9Ti is recommended for other media.

The service pressure of stainless steel spiral wound gasket with flexible graphite in gas medium is 14.7MPa (up to 19.6MPa in China), and it can be up to 30MPa in liquid. Temperature: – 190~+600 ℃ (available to 1000 ℃ under oxygen-free and low-pressure conditions).

Polytetrafluoroethylene has good low temperature resistance, and its yield strength at low temperature is much higher than that at normal temperature. Therefore, PTFE spiral wound gasket can be used for low-temperature medium, such as liquid hydrocarbon. At the same time, due to the addition of metal tape to improve the thermal conductivity, the service temperature of PTFE spiral wound gasket can reach 250 ℃ and can reach 9MPa and 200 ℃ in acidic media.

Spiral wound gasket is suitable for heat exchanger, reactor, pipeline, valve, pump inlet and outlet flange with large pressure and temperature fluctuation. For those with medium pressure and temperature above 300 ℃, inner ring, outer ring or inner and outer ring shall be considered. If concave and convex flange is used, the effect of winding gasket with inner ring is better.

The sealing effect can also be achieved by covering the flexible graphite plate on both sides of the flexible graphite spiral wound gasket.

07 Metal Flat Gasket and Metal Corrugated Gasket

It is generally used on medium and high-pressure valves, pipes and equipment flanges with small diameter. The service pressure is 1.568~31.36MPa for the former and 1.568~3.92MPa for the latter according to the temperature. The gasket material is selected according to the medium and temperature.

08 Octagonal Gasket and Oval Gasket

The octagonal gasket and elliptical gasket (commonly known as “earth steel ring” in oil refining industry) used for trapezoidal groove flange have good sealing performance. On the conical surface of the groove, the octagonal gasket is in face contact while the elliptical gasket is in line contact. Therefore, the elliptical gasket has good adhesion under low tightening force, but it needs to be tightened twice; However, octagonal gasket is not easy to leak after being fastened at one time. Their disadvantage is that they require a large bolt tightening force. When used in low pressure and high temperature conditions, the flange grade must be above PN 25 kg.

Post time: Mar-17-2023