How to Convert Pressure from Bolt Tension to Torque

Tension (elongation) is the real determination of a bolt's "tightness".

The amount of torque applied to a bolt head,or nut does not indicate the amount of tension applied to the joint.

Too many variables affect the mating/torquing operation. I have no idea how to convert.

that mean we should be follow pressure value as MFG supply and apply hydraulic torque follow perssure recommended right?

I'm sorry, the language barrier is too great.

You do not have to be concerned with the tension level present within the bolt. In making up the flange the correct amount of sealing pressure must be applied to the gasketed joint. The manufacturer (in this case your relief valve supplier) will specify the amount of torque you need to apply in tightening (sometimes called tensioning) the bolts to get the correct gasket loading. The metallurgy of the bolting and the mating flanges, and the design of the gasket must be consistent with the given torque specifications. A suitable torque wrench should be used to make up the flanged joints.

Please be more explicit and then you can get the right answer. As you formulate the question it is not clear what you have and what you want.