Helpyou,
Where are you and where is this project?
What size is the Valve (by this I mean the pipe size)
What type of valve is This?
How old is this Valve?
What is the commodity in the line
What is the operating pressure and temperature?


Sometimes its possible to do all the right things and still get bad results

...how fast does the valve need to operate, how often, what is the duty (modulating/throttling or open/close)? What power source(s) are available/preferred?

HI pennpiper & btrueblood

thank you for your replies & questions. Please see my reply to your questions below.

Project is in middleeast
pipe and valve size 24 inch
still retrieving datasheet, most likely its gate valve. I will confirm once i get datasheet
20-25 years old
Liquified natural gas (-161C, 3-4 bar)
valve should open within minuts 1 - 3 minutes
how often? around four times per month, duty is to open fully.
power source is from a nearby substation/control room.

Thank you

First and foremost you need to find the valve data sheet from the vendor.

A valve designed for manual operation may not be suited for actuated operation. Actuators can often supply much higher torque or force than an manual gearbox and can weigh a lot more.

Your next task is to find the original vendor and see if they are still operating and ask them for a conversion kit.

Electric actuators are easier than hydraulic or air for gate valves.

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

First, to prepare a data sheet for the valve requirements with the instrument safety rating, and contact the vendor for the proposal. Also, check what is the lead time of the valve.
Second, to check the existing MCC for the excess power source as needed for the MOV load.

Quote:

excess power source as needed for the MOV load

I'd be surprised to find a valve operator taking minutes to cycle a valve, using more than a few hundred watts.

Keith Cress
kcress - http://www.flaminsystems.com

After 25 years, now it is decided to install motor(s) . Sounds familiar.
Similar situation, my Operators' reasons was either:
- To improve the leakage rate...they think powerful motor will be able to wedge the disc more against the seat. This is not necessarily true
- Less operators' task to go outside (and turn the hand-wheel for 10-20 minutes..estimated time for 24").
IMO..the idea of having fully open/close within 3 minutes is a bit vague for old valves. Unless for some reason, now being attributed as safety function. Just bought 24" valves with Rotork actuator, incorporating safety factor (for spindle) of 1.5, the closing and opening time is around 4-6 minutes. With all due respect, they never had any problem with 10 minutes before this project was initiated.

In general, things to be considered are:
- What general valve condition (internal passing, stem corroded, etc.)? and whether this is still acceptable by your engineers (mechanical, process, etc.).
- safety factor applied for sizing the actuator?
- ISO flange to mount the 'new' actuator. Does modification required? what material is the yoke..if this is cast iron then it would be really challenging to do the welding..is it possible to install adapter flange?
- Agreement on the travel time by technologist, process engineer, mechanical and motor supplier!! You can always have faster travel time but this would correspond to bigger motor.
- Are you going to modify this on-line or at workshop?

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&f...

The first thing I would suggest is to contact the valve manufacturer as usually they have already done this and have motors and specifications for different environments to cover the necessary torque and mounting options. There are also motors out there, Rotork as an example, that have motors that can be set to open/close at whatever time period the customer wants. It just comes down to what options you want and what you want to pay for!

You might also ask if the valve is already equiped with a gearbox.
If so, it will be way easier to put an actuator on it.

Apparently you have most of the data you might need.

ISO couplig for actuator might be an issue for you as low-tier valve makers sometime don't sell ISO coupling on manual gate valves if not specified by the client.
With a picture of the valve you will be able to see if you have an ISO coupling on the valve or not.

If you can't find data on your valve, torque will be your next issue.
In an usual actuator request for quotation datasheet, you need to provide the break to close torque (BTC), break to open torque (BTO), running torque (RT) and Maximum Allowable Stem Torque (MAST) of the valve. The actuator must provide more torque than needed by the BTC and BTO cases, but not more torque than the MAST of the valve because you don't want to cause a major accident in your process.
It is possible to measure your BTC and BTO torque on an existing valve. But you can't measure the MAST, it depends on the material and dimensions of the stem.
Usual MAST is 3 times the higher torque needed in BTC or BTO case.

Hopefully you can find a solution with all those advices.