Gate valve with "thousands" turned

[Danlap]

Dear respected valve practitioner,

I have only dealt with a dozen of these kind of (thousands turns) valves, and I am still wondering what was the initial reason for designing valve or gearbox with such “slow” linear movement.
Even after being refurbished, a 42”-150# Gate valve (for geothermal application years back) still required almost 1 hr to fully open/close it from fully close/open position. And that was even with the help hand-drilled gun with socket drive. 3 handwheel rotation for 1 mm linier movement.
Picture below is 24”-600# gate valve for Methanation process though. And claimed to be required approximately 3 hours to fully close/open the valve, if the valve is moving.
Having young operator with less patience and same (but getting older) valve with less reliability, thus the production team lead or asset owner getting more and more frustrated and wandering whether this kind of valve is still suitable for faster pace production.

Question:
- What was the reason / design basis?
Was it DeltaP and torque required to break open the valve? Was the gearbox with bigger Mechanical Advantage (MA) ratio in the 80’s so big, therefore not preferred weight-wise? Is it the spindle diameter? Etc.
- If I change the gearbox with bigger MA ratio, what would be the consideration factor?

Thank you in advance for the constructive reply.

Kind regards,
MR

https://nosuchvalve.com

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

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[LittleInch]

You've basically answered your own question.

you would need to dig out the valve actuator data sheet and calculations, if they still exist, or start afresh with the valve open and closure force details.

That is a pretty big valve you have so the peak open and closure forces might be quite high, especially if you apply some factors for aging and time. Hence that develops your gearbox ratio based on a handwheel diameter and maximum operator force of 50N at the outside.

Hence the gearing is designed for a one time max break force and unfortunately then results in an excessive number of turns of the wheel to open and close the damned thing.

I think most of us at some time have had to spend 30,40,50 minutes turning hand wheels which almost fly round in free wheel for 99% of the travel....

bottom line - unless you only open and close this ting once a year, put some sort of actuator or detach the handwheel and apply a much faster motor actuator to the gearbox drive and run it at 10-50 times faster than you can do it by hand. Then if you actually need the one time high torque, re-engage the handwheel.

Probably need to talk to vendors like rotork or

https://www.totallockout.com/expertise/valve-assist/

http://www.rotork.com/en/product/index/multiturngearboxes

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