Extended stem valves
Extended stem valves
(OP)
Where can I find advantages and disadvantages of extended stem valves?
Is it a Good Engineering Practice to use extended stem valves?
Is it a Good Engineering Practice to use extended stem valves?





RE: Extended stem valves
Extended Bonnet has a different meaning. Its function is to "isolate" the gland from the high or low temperature zone so as to maintain integrity of the stem seal and the operation of the valve.
Best practice definition of low & high temperature should extended bonnet applied is normally depends on Plant's best practice. below -50 deg C and Or above 200 deg C may requires bonnet extension.
Yes, Graphite (standard) could withstand lower or higher then that, however shall it requires to operate the valve during emergency (before gland packing could establish itself towards ambient temperature of -20 up to let say 100 deg Celcius) experiences shows that this repetitive actions will disrupt gland integrity. Then of course leaks or burst through "stem".
RE: Extended stem valves
Thanks Muktiadi
RE: Extended stem valves
to add into perspective. Shall valve and or its medium temperature is higher than 400 deg Celcius, thus requires a very long extended bonnet in order to maintain Gland Packing temperature. Then Heat Dissipation Bonnet could also be used.
Answering your first question, it is generally stipulated in ASTM C1696.
However yes, generally it is best practice. The combination of Gland material, heat dissipation / extended bonnet material and Operation behavior (whether they operate the valve at the lowest or highest design temperature) are driven by Manufacturers' R&D and also End user.
RE: Extended stem valves
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat