Opening and closing gate valve

[thunderspeed]

If the case is the gate valve disk is stuck open ( or not totally stuck but heavy )
WhenI come to move hand wheel , would the handwheel slide up the stem ? Or still only stem would move down . And what forces hand wheel from climbing up the stem in this case ?

 

[Danlap]

Hi thunderspeed,

Your question is very general and also common in the industry.
I am afraid nobody can really provide the exact answer accept the ones that in direct contact with the valve (your maintenance/operation department).
Despite you're not totally clear describing the condition (valve type? wedge/slab/double-expanding, etc.; service medium?; material?; how old is the valve?; do you have the GA drawing?), I will try to provide some basic guidance and provide some hints that may or may not answer your question entirely.

a. Can you do radio graphic/x-ray on the valve? PS: doing this on carbon steel valve is not appropriate as you can only see black images on the result.
Does your wedge still intact with the spindle?
Stem/spindle (arguable comments) is the weakest link on the valve. Within times / exposed to excessive force frequently / wedge stuck due to something may broke/detach the spindle from the wedge. Once detached, your spindle may be rotating but your wedge relatively will stay on its stuck/last known position.

b. I assume you don't have any document. But for sure someone has been operating this valve for years. Ask them how many hand-wheel turn required to move 1 pitch of the spindle?
If this is one of those big gate valve with (me being exaggerate) that requires tens/hundreds of turns to move the spindle even for 1 pitch. Then don't bother to observe the movement

And many other possible scenario

Now your question:
Why is it heavy (common problems):
- Gland packing re-tightened (normally without control) in a way so add friction a lot
- the position of the Seat - wedge - spindle must be straight. For some reason its not
- Some medium hardened in some condition, thus cause sticky surface. In some rare condition (some alien material carried over) after commissioning and get stuck (e.g. welding gun, paint roll, dead cat, etc.)

When I come to move hand wheel , would the hand-wheel slide up the stem ? Or still only stem would move down .
--> Is this vertical / horizontal orientation? If the spindle still attach with the wedge, yes any rotation on the hand-wheel will move the wedge accordingly.
If its vertical, and somebody decide to "shake the gate valve" plus the its already detached with stem, there is a good possibility you may end up with stuck close

And what forces hand wheel from climbing up the stem in this case ?
--> really depend on the MAST and rim-pull design force. Ergonomic approach is for hand-wheel larger than 5 in. should not be more than 150 N.

Simple solution is to replace the valve, or do hot tapping (add another "stem" from below until next opportunity to replace the valve).

Just some thoughts,
Regards,
MR

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

 

[LittleInch]

thunderspeed

You really need to find a sectional drawing of your valve, but for an external rising stem gate valve, see picture below. The thing stopping the handle climbing the stem is the yellow collar which is restrained in the vertical direction and is the bit which the hand wheel actually rotates.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.