Instrumentation and Process Control

Globe control valves body is jointed with its applicable bonnet with a bolt and nuts just like two pipe jointed together with a flange. However, the gasket type in the control valve is differing from the general manual globe valve. The body/bonnet gasket in the manual globe valve is just like flange gasket which has flat, spiral wound, or ring type gasket, contrary the body/bonnet gasket in the control valve usually didn’t have this kind of gasket.

This differentiation is caused by the body design of manual valve and control valve. In the manual valve, the body and bonnet is exposed directly to the fluid service. In the control valve, the contact between bonnet and fluid service is very minimal (due to cage or plug design) so that only a small portion of bonnet part contact with the fluid and will make different seal force requirement. See example pictures below for more clear description.

As a default we could specify the body/bonnet gasket type and material as per body material (or 316 SS spiral wound/graphite filler) with the spiral wound type for all class.

In the end, we must consult manufacturer regarding this gasket type to get the most suitability of gasket type with the service condition and valve class rating.