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Working Conditions (Pressure)

February 07, 2019

Written By:
John Tomme

Working Conditions

When working pressures are too high seal extrusion can occur through the gap between the piston and the cylinder, also the rod and the gland, this would dramatically affect the life of the seal. In order to avoid possible extrusion, all materials used in seal manufacture must have mechanical resistant properties which prevent seal extrusion in very high-pressure conditions, even when consideration has been given to the end floats shown in the following diagrams.

Figure P-1 (Seal design enable fluid pressure (P) to be transmitted through the seal and maintain perfect alignment of the anti-extrusion ring eliminating all extrusion gaps, even when radial force (pm) side loading occurs.)

Figure P-2 (A separate ring and seal assembly are not able to adapt to misalignment and a wide extrusion gap is created causing seal extrusion and excessive friction.

Anti-extrusion rings and guide rings are manufactured in acetal resin, inserted into rubber seals reinforced with fabric capable of withstanding very high-pressure conditions in either static or dynamic applications, and maintains perfect centering even when misalignment occurs between moving parts.

Figure P-3 (By transmitting the fluid pressure through the seal, constant adhesion of the anti-extrusion guide ring to the cylinder wall is assured, even through pressure changes.)

Figure P-4 (The guide ring is not incorporated in the seal and will not be sensitive to side loading (Pm). Misalignment of the piston cannot be compensated by the guide rings and phenomenal extrusion will take place.)

An effective anti-extrusion guide ring is energized by the seal and compensates for radial float changes due to wear and cylinder deformation caused by pressure variations. Anti-extrusion rings and guide rings are always incorporated in the seal itself and give perfect adhesion to the metal surfaces in any pressure conditions. Only this method will give complete extrusion protection and correct alignment.