1" Cl.1500 Flanged Globe valve with RTJ bolted cover,due to space constrains Hex cap screw was used,is it ok or should i change to Stud with 2 nut at joint
Not knowing why the space limitation for using stud bolts.
IMO, you should check the bolting strength if using machine bolts instead of the stud bolt as specified by the Code.
hex is fine, if you force the nut and bolt with constraints, you will just end up with an improperly tightened bolt, leading to failure. api 602 valve bonnets are commonly tightened with cap screws.