GBTorpenhow
Mechanical
- Jan 26, 2022
- 257
Service: 50/50 water/propylene glycol, design 150 psig @ -20 to 150F, oper. 30-80 psig 80-120F
Valve: Class 125 lug style concentric butterfly, API 609 Cat. A, cast iron body with integral EPDM seat/gasket
Mating flanges: B16.5 Class 150 A105 RF
Curious what others prefer for bolting for this type of valve.
The incumbent solution is to use the same A193 B7/A194 2H stud/nut combo as the rest of the piping. My concerns with this are:
A) high strength B7 bolting isn't close to being required based on the valve vendor's torque spec to seal the EPDM seat/gasket of these valves
B) the valve thicknesses in the range of sizes that we are dealing with (up to 12" NPS or so) are such that it isn't going to be possible to fully engage a high strength bolt in a cast iron body (by fully engaged I mean that the bolt is threaded enough that the bolt shank will yield before the internal thread does). Functionally, if the field contractor mistakenly uses the 'default' torque spec meant to seat a regular nitrile sheet gasket they can easily damage the valve.
C) I prefer a headed bolt, ideally a hex cap screw, here vs studs whenever feasible for a tapped hole because I trust the engineer (myself) to specify the right bolt length more than I trust someone in the field to correctly install a stud with one nut into a tapped hole with the correct engagement length.
Valve: Class 125 lug style concentric butterfly, API 609 Cat. A, cast iron body with integral EPDM seat/gasket
Mating flanges: B16.5 Class 150 A105 RF
Curious what others prefer for bolting for this type of valve.
The incumbent solution is to use the same A193 B7/A194 2H stud/nut combo as the rest of the piping. My concerns with this are:
A) high strength B7 bolting isn't close to being required based on the valve vendor's torque spec to seal the EPDM seat/gasket of these valves
B) the valve thicknesses in the range of sizes that we are dealing with (up to 12" NPS or so) are such that it isn't going to be possible to fully engage a high strength bolt in a cast iron body (by fully engaged I mean that the bolt is threaded enough that the bolt shank will yield before the internal thread does). Functionally, if the field contractor mistakenly uses the 'default' torque spec meant to seat a regular nitrile sheet gasket they can easily damage the valve.
C) I prefer a headed bolt, ideally a hex cap screw, here vs studs whenever feasible for a tapped hole because I trust the engineer (myself) to specify the right bolt length more than I trust someone in the field to correctly install a stud with one nut into a tapped hole with the correct engagement length.