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?