manual gate valve position

[panthripu]

Hi guys
I am trying to find out the easy ways to get a open feedback from a manual gate valve which is operated by the wheel manually.The valve shaft does not move physically up or down when it is opened or closed during rotation.
One of the plan is to fix some actuator on the shaft which will actuate a limit and each actuation is to be counted and compared to get open signal. Any other suggestion from experts here ??

 

[Tom Jenkins]

If it's a gate valve the shaft generally does move up and down, but it is enclosed inside the valve housing so you can't see it. There are nonrising stem types but they are uncommon.

My first suggestion is to contact the valve manufacturer. Most of them have standard limit switch packs that can be field retrofitted for position indication.

 

[iant]

if there is no actuator kit you may try an encoder
the idea of counting rotations will work but the encoder will be more accurate
I assuming this is a gate valve with multiple turns to open and close - not a 90 deg rotation type.

 

[Roy Matson]

some sort of proximity switch sensing the gate position, even if the shaft doesn't move the gate certainly does
Roy

 

[1MoCast]

Just thinkin... Is there any merit to sensing the result of the valve? Pressure, differential pressure or a wet sensor?

 

[leitmotif]

I think monitoring "percent open" will not deliver what you want to do.
"Percent open" as measured by either height of handwheel or turns of shaft will not give you a linear relationship with flow. Cross sectional area of "open" will vary.

Seems to me you should be monitoring flow.

Dan

 

[Tom Jenkins]

A little valve info - gate valves are usually used for on/off service only. They make lousy throttling devices and if panthripu is trying to get a flow rate from valve position he is in trouble anyway.

I expect that all he needs is open/closed indication so a limit switch or prox switch would be the way to go. If it is a non-rising stem type then, barring a manufacturer's kit, a prox swithc to pick up the gate at the top of the stroke might work. It would have to be tapped into the bonnet, so it would need a pressure rating to match the process fluid conditions.