Broken valve stem
Broken valve stem
(OP)
If a valve stem is broken, can it be welded back together in field?
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RE: Broken valve stem
Just how big and expensive and far away in time is your replacement?
Mike Halloran
Pembroke Pines, FL, USA
RE: Broken valve stem
I agree with Mike, but what other problems do you actually have?
Valve stuck and tried forced open or shut, or just too bad or weak construction, bad maintenance or wrong valve? Sealings for valve-seat and stem?
Will the valve actually do the job if you only repair the stem, and in case for how long?
RE: Broken valve stem
If the valve is a rotary control valve there is a greater-than-small possibility that the stem is heat-treated (17-4 PH) which will be damaged in the heat-affected zone. You had better get a new, proper metallurgy stem on an airplane to you right NOW.
RE: Broken valve stem
RE: Broken valve stem
it may always be useful to learn from failures: if you could add some more information about the occurrence in object, probably we may suggest something about possible causes and, in the end, we... all may learn something more
Is the valve a rising stem or a quarter turn one? Small or big diameter? High or low pressure class? Is the packing made of graphite rings?
How about the materials selection?
And the chemical nature of the medium inside?
Did you contact the valve Manufacturer already?
Sorry if I bother you... even if you can't answer the questions above, thank you anyway!!
Bye, 'NGL
RE: Broken valve stem
This valve is rising stem gate valve. It is used in our 50lb condensate. I cannot find the manufacture of this this valve. So I don't know what the stem material is. But there is no bending on the stem. So I don't think it is broken because of bending.
RE: Broken valve stem
I have a new question, if we remove the top part of the broken stem, can the pressure of the line push the rest of stem and open the valve? The line pressure is running at 50psig. Valve size is 6".
RE: Broken valve stem
All could contribute to extra mechanical forces on the stem, along with temperature variations and corrosion.
Theoretically the disc can under circumstances be forced up.
The stem broken at the packing seems to indicate one, or several in combination, of a series of possibillities:
Prior material weakness / wrong material or construction / faulty machining ?
Broken at point where largest torque forces (?) turning resistance (lower part of stem stuck?)
Stem movement skew (faulty packing, bosses (to wide) etc)
Repetitive forces, weakened material by age / temperature / corrosion at packing?
Valve stem forced by using extra leverage on handwheel?
Valve generally weakened by (repetitive) unfavourable conditions in pipeline.
.... and so on.
RE: Broken valve stem
Throttling with the valve partially open could have caused the plug to vibrate in resonance and fatigue the stem, or rattle pieces against each other to cause galling or fretting, or even simple frictional wear. Isolation valves do not have the positive guiding that throttling valves have designed into them.
otherwise, something must have seized and the maintenance gorillas used a long cheater to try to break it loose.