The Role of the Support Ring in the Valve Sealing Structure and Processing Points of Attention

Support ring such parts, in the whole seal structure belongs to the ‘hidden’ key parts. Many users do not pay much attention to it, but in fact, once the design or processing is not in place, the compression force distribution of the valve seat seal, PTFE ring will have a great impact, especially in the high-pressure or temperature fluctuations in the environment more obvious.

We have previously dealt with a North African customer's project, the valve seat uses a bi-directional metal + flexible seal composite structure, PTFE ring in the initial installation is no problem, but running a few months after the discovery of the sealing performance degradation, and even extrusion deformation of the seal. After returning to the factory for autopsy, it was found that the problem was the deviation of the thickness of the support ring + the inner chamfer was too deep, resulting in uneven force.

For this situation, we give the following suggestions: First, the support ring processing can not just ‘according to the drawing of a circle’, the key lies in the tolerance control and chamfering direction; Second, according to the compression rate of the sealing material to leave a compression margin, especially in the metal shell of the pipeline with frequent expansion and contraction of the support ring once the mating surface is loose, it is easy to The pressure will easily deviate from the soft seal.

In the processing stage, the support ring is recommended to be roughly turned from finished bushings or solid-core forgings, and the outer circle, inner hole and step should be completed in one clamping to control the runout and concentricity. When we turn this kind of parts, we generally control the surface roughness within Ra 1.6, the key surface Ra 0.8, chamfering direction according to the direction of assembly to avoid damage to the edge of the seal ring.

Although the price of support ring is not high, but it has a big impact on the stability of the whole valve seal. It is recommended that the customer in the drawing stage to clarify the assembly sequence, compression stroke and datum position, if necessary, to provide the valve seat or valve body with the structure of the diagram, so that we linkage assessment of the overall structural effect. Our side can also assist in simulating the hot fit state, in advance to judge the risk of seal displacement under high pressure or high temperature.