I am working for a company that wants me to setup a Chart. It is so they can give to contractors to tell them what maximum valve class they are allowed to use for hydrotest purposes.

Example:

Such as Socket Weld Valve 800 class bolted bonnet API trim #8 is good to a maximum hydrotesting pressure of 1400 psi temp range 35 F to 120 F

And being that valves are not my area of knowlegde I need some help to setup this chart. The pupose of this chart is to ensure safety when using hydrotest tree of the right pressure rating.

F.Y.I. Contractor was using 800 class vales on 3300 psi hydrotest.

It is a common misunderstanding that valves legally can be used above the allowable operating pressure/temperature clearly stated by the norm the valves are produced and tested after.

If you ask the producer he will give you the relevant pressure temperature curve according to the correct class.

The misunderstanding occurs because the valve body is normally tested (at a given temperature) at a pressure about 1,5 times higher than allowable operation pressure (variations according to class, norm (European, Asian, US and others) and type). The body test is done with valve open.

The seat thightness test is made at max operating pressure, or at about 1.1 times this (again variations, and factories might allow higher, but again according to type).

The clue is to stick to the values given in the class norm, or get the manufacturer to guarantee the safe use at higer values.

Everything else is your own responsibility if anything goes wrong.

PS. I haven't checked your valve class at the temperature and pressure mentioned, let the producer have his say or get the relevant curve by net. If the producers says OK, but values are above allowed, you have still the rest of you rig to check...

In the US, ASME B16.34 Specifies the Maximum Pressure/Temp limits for various ferrous alloys.  If you're only using the valves for run a hydro-test fixture, then you probably only care abour Carbon Steel ASTM A216WCB Group 1.1 (Page 27).  If you have a cleanliness standard you might be interested in 316SS, Group 2.2, ASTM A351CF8M. Page 48.
Example: Carbon Steel class 150 is rated to 285 PSI at 100F.  Testing is to 50% greater than that.  427.5 psi.  But that is testing for THAT VALVE.  The valves to control the pressure to the teat valve must be used within their normal operating range.  Only the test valve is tested with overpressure, and even then the duration is limited by the standard.  

There are many seat leakage standards and each has its own testing procedure. Example: FCI70.2 is the favored test procedure for control valves and most classes are tested only at 50 psi.  MSS SP61 tests at full operating pressure.  I Believe the API standards also test at full pressure.  Pick one, or use the one your customer demands.

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