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Commentator

Join Date: Dec 2006
Location: South Florida
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Water Hydraulic positioner

01/14/2007 12:10 PM

Does anyone know of a hydraulic positioner that will work with potable water as the hydraulic fluid? The closest I've found is one that works with a water/glycol mix. The application is for a butterfly valve (16") with a 4-20 mADC control signal.

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Anonymous Poster
#1

Re: Water Hydraulic positioner

01/14/2007 12:18 PM

the only problem will be corrosion and debris (sediment, etc.) in the potable water will muk things up unless you filter it AND make certain all the wetted parts are compatible with your 'potable' water.

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Commentator

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#2
In reply to #1

Re: Water Hydraulic positioner

01/14/2007 12:53 PM

There is already a sediment trap filter on the supply and the potable water is what comes out of the tap. Currently the application uses solenoid valves for position control of the hydraulic piston so that is not a problem. I want to replace the solenoids with a device similar to an I/H converter for true analog control.

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Associate

Join Date: Jul 2006
Posts: 35
#3

Re: Water Hydraulic positioner

01/15/2007 5:48 AM

Kinetrol (www.kinetrol.com) have a range of 316 stainless steel, double acting, quarter turn actuators, providing up to 50.5Nm at 7 bar. They are designed as pneumatic, but have been used successfully on water. You will need to guard against water hammer to avoid damage to the unit.

Might be worth a look.

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Guru

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#4

Re: Water Hydraulic positioner

01/16/2007 9:57 PM

Just curious, but why do you need water to power the actuator?There are I/P converters that will allow very precise control of nearly any type flow, using instrument air pressure. If 3-15 PSI won't do it, there are ratio relays that can scale the output to any desired level. I have used pneumatics successfully on large valves at water filter plants for backflush cycles: lo flow, hi-flow, etc.using 4/20 ma and 3-15psi.

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Commentator

Join Date: Dec 2006
Location: South Florida
Posts: 92
#5
In reply to #4

Re: Water Hydraulic positioner

01/17/2007 8:06 AM

You are correct however this is an existing installation that uses water as the control signal. As I explained previously the analog control is currently being controlled with two solenoid valves and a PLC resident algorithm to approximate PID control by learning the flow curve as the process changes. I developed the algorithm as a contractor under a fixed price contract. It works, pretty well actually, but I've never been completely satisfied with it, especially at the low end of the flow curve. The client is going to be replacing the PLCs sometime in the near future and I am attempting to find a solution to upgrade the controls to something that will use true PID control. Here is the driving force. There are nearly 200 of these installations spread out over two 10 acre buildings. The central hallway/pipe gallery of each building is 1/8 mile long. I haven't done a cost estimate but, if there is such a device that will work and last, the retrofit will be much less expensive than doing the design, putting it out for bid, running all the instrument air lines and buying the the pneumatic positioners with I/P converters.

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Anonymous Poster
#6
In reply to #5

Re: Water Hydraulic positioner

01/18/2007 8:42 PM

What type flow meters are you using? Do you have a centrallized control for all the valves, or is the monitoring and control at each valve?

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Commentator

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Location: South Florida
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#7
In reply to #6

Re: Water Hydraulic positioner

01/19/2007 7:23 AM

{What type flow meters are you using? Do you have a centrallized control for all the valves, or is the monitoring and control at each valve?}

Venturi and DP cell. There is no analog position feedback from the valve just limit switch. Monitoring and control from PLCs.

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Anonymous Poster
#8
In reply to #7

Re: Water Hydraulic positioner

01/19/2007 8:47 PM

Is the actuator a double-acting cylinder, or spring loaded in one direction?

How much water pressure is available?

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Commentator

Join Date: Dec 2006
Location: South Florida
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#9
In reply to #8

Re: Water Hydraulic positioner

01/20/2007 3:33 PM

Double acting. I'm not certain without verification but I believe it is in the range of 50 to 60 psi.

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Anonymous Poster
#10
In reply to #9

Re: Water Hydraulic positioner

01/20/2007 5:08 PM

Have you considered an electrically powered valve actuator?There are plenty available with 4/20 ma feedback, some with a microcontroller built in to handle the conversion on the output end to the motor.

Here is one link, but there are many others

http://www.crtec.com/?action=doc.main&id=41&gclid=CILnhfz_74kCFU5xFQodnhZ9Lg

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Commentator

Join Date: Dec 2006
Location: South Florida
Posts: 92
#11
In reply to #10

Re: Water Hydraulic positioner

01/20/2007 5:33 PM

I don't intend to be rude with this but I've stated at least twice that this is for nearly two hundred valves. Easy solutions like a pneumatic positoner with an I/P or an electric positioner by Limitorque or Rotork or whoever are a no-brainer. As of this June I will have 30 years of experience in the Instrumentation and Controls field. What I'm looking for is a unique product for a specific application.

I do appreciate the interest but it would help if you would please read through the entire thread for the specifics.

Thanks anyway.

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Anonymous Poster
#12
In reply to #9

Re: Water Hydraulic positioner

01/20/2007 6:15 PM

Taylor-Sybron (Rochester, NY) used to make specialty controls, but they may have been bought out by another company by now, but worth researching. Also Foxboro, Johnson Controls,and Honeywell would probably be good bets.I have been out of the process control field for a few years now, and I know things have changed a lot. Of course, you probably are familiar with these companies since you've been in the field as long as I was.So basically, you want a I/H converter with double-acting output,that you can use with the existing actuators, to minimize cost.I will ask around some colleagues and post you if I find a solution.

Good Luck!

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Commentator

Join Date: Dec 2006
Location: South Florida
Posts: 92
#13
In reply to #12

Re: Water Hydraulic positioner

01/20/2007 6:22 PM

The caveat is the "H" has to handle water. Just guessing before looking but Taylor-Syborn is probably the Taylor Controls from way back. I rarely can keep up with who is owned by who anymore and don't try very hard until I need to.

Thanks for the interest in my little task.

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