I've recently starting working with the AOV program at my facility and have come across something that seems off to me. I'd appreciate the group's input.

After we reinstall an actuator, following valve maintenance for example, and while we are consolidating the new packing and heading toward the torque spec we also have our diagnostic equipment hooked up looking at, among other things, stem friction.

Where this has led us a great many times is hitting engineering's friction limit before we reach the packing torque spec. At that point engineering often instructs the technicians to not torque the packing gland nuts any further and to return the valve to service.

Is this a common practice elsewhere? I can't wrap my head around failing to achieve packing torque specs because of stem friction. I get the interplay, but aren't we just setting ourselves up for more leaks than is necessary? Shouldn't we be addressing the actual reasons for the stem friction rather than sacrificing packing torque?

Thanks....

 

You'll have to consult your valve actuator supplier. If the designs are not properly coordinated, and suitable for the process conditions, failure is guaranteed...