Force to Squeeze an O-Ring

[oneeyedwitchdoctor]

I am working on a check valve that has an o-ring in a groove on a conical (30deg) face and uses a spring to energize the seal. Does anybody know how I can estimate the required force (hence which spring to use) to energise the o-ring seal.

 

[flexibox]

If you are talking about "C" section Orings with springs inside I recommend that you buy a standard off the shelf Seal. I assume you have a PTFE seal and want to insert a spring inside? Is this original supply?