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[Lukas Schmitt]

I’m reverse-engineering a small hydraulic shutoff valve used in an industrial test stand, and I’m trying to understand whether the face-sealing setup for the poppet is causing a recurring internal leak. The poppet uses an X-ring in a machined groove, and when the valve closes, the X-ring is pushed against a curved sealing surface rather than a flat, perpendicular land. The return spring is fairly light, so the contact load on the X-ring isn’t high to begin with. For those who’ve designed face seals with X-rings before: is it normal for an X-ring to seal reliably against a curved seat, or does this kind of geometry typically lead to inconsistent contact and leakage?

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[Matthias Huber]

I’m not sure that the x-ring with the curved sealing face is your issue. One of the key advantages of using an X-ring over an O-ring is that it has multiple lobes (rather than one) and therefore has additional sealing surfaces. So I expect that it would manage the curved sealing surface ok. What worries me is your comment about the return spring being light. I would look at whether your leaks are due to not getting enough compression force on the x-ring.

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