Valves are a critical component in process control applications, where they are used to control the flow of liquids and gasses by opening, closing or partially obstructing the flow.
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As industrial automation and control systems have advanced, so too have the methods for controlling valves. Today, many businesses rely on automated valve solutions to position their valves without requiring manual operation. These valves utilize pneumatic, electric or hydraulic actuators to provide precise and reliable control of valve position, making them an integral part of many piping systems.
But with so many types of valve actuators available on the market, it can be challenging to determine which one is right for your specific application. Continue reading for an overview of the most common types of valve actuators, so you can make an informed decision when selecting the best one for your needs.
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Help with shutoff valve/actuator selection for water service
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(Mechanical)
(OP)
25 Jun 11 08:39Hello all,
I am new to the valve/actuator game and am trying to learn quickly on the job regarding the ins and outs of the various options. I have tried talking to various vendors learn more, but I get the run around (distributors say to talk to the manufacturers who say to talk to the distributors, etc). Very frustrating, especially when I am under the gun to get something out.
I have a specific application that I have been looking into in order to evaluate the possibilities so that I can recommend a solution to a customer. My hope is that those of you with experience can help me with this application and I can learn in the process.
The application is for a 10-300# valve that is used for shut off (on/off) service. The key parameters are:
-Raw river water with typical debris (leaves, twigs, pine needles, decomposed granite, etc)
-Normally the valve will be used during maintenance to shut off the flow to work on downstream equipment.
-the valve will not typically be used very often, say once a year during PM.
-The valve needs to be actuated so that in the case of a downstream piping breach, the valve can be automatically closed to prevent flooding. The trigger will be a float type switch.
-This shutoff actuation needs to operate in a plant blackout situation.
-There are various sourced of power available for the actuator. 1/3phase AC power, air, but I lean towards electric. there is also DC power available with a battery back-up but it is used for many other things in the case of a blackout, so using it would have to be well justified.
-the customer stated a desire for a remote control box so that an operator can close the valve from the top of the stairwell so he doesn't have to wade through any standing water to get to the valve.
The typical valve type used in this plant for this service is a metal seat wedge gate valve and I think the preference would be to stay with this type. The problem is with the actuation. Due to the multiturn nature of the gate valve, an electric actuator seems to be the way to go, except for the requirement for blackout remote operation. I am not sure what is available for options on a pneumatic actuators on multiturn valves. What pneumatic actuators I have found are cylinder type with limited stroke that cannot operate the multiturn.
I have looked at other valves. Globe is out because they are not really shutoff valves and typically multiturn.
I have looked at quarter turn valves to open-up possibilities for actuation. This now can be either electric or pneumatic. On the pneumatic side now I can can have a pneumatic spring return actuator.
This would be butterfly and ball. From what I can see a butterfly is not the best solution since there is some debris that could get hung-up on the disc, wear the seals and potentially stop the valve from completely closing.
That leaves a ball valve. As I understand it a ball valve is typically quite a bit more expensive and require more space than either a gate or butterfly valve, but because it is so difficult to get prices of various valve to compare I cannot really back this up.
I then have to evaluate the relative costs of the various feasible solutions, but again getting my hands on valve/actuator costs has proven very frustrating, especially when I cannot identify very well the specific part numbers.
I am pretty sure you folks that have years of experience can answer many of these questions quite easily, and I would appreciate any insight anyone can give into this.
Thanks
(Materials)
25 Jun 11 12:13Vehazle,
If you want a multi-turn actuator you need to look into a "diaphragm" type actuator. They are pneumatic and are available with a spring return feature that will close the valve in the event that the air-supply is lost.
I dont think that electric is the way to go, simply because most, if not all, electric multi-turns are not available with a spring return feature. If there is an emergency situation and power goes down, you will not be able to operate the valve. I suppose you could use the DC system, but the pneumatic system sounds like it's probably a better option.
I am in agreement that a ball valve or butterfly valve is not the way to go. A ball valve would work, but your actuator will need to be considerably larger and thus more expensive. Also, you are correct, you will need more space if you are going to use a ball valve.
You might consider looking into a "knife" gate. It is preferable over a "slab" or "wedge" gate in this scenario. they are often used to control water where typical debris are present (rivers, irrigation systems, sewage, etc.)
good luck!
-vrf
(Mechanical)
25 Jun 11 18:52With river water, silt and debris can get in behind the ball and greatly increase the operating torque. There are ball valves that can minimize that, but they are spendy.
Electrics that have spring actuators have size limitations since the electric actuation has to overcome not only valve torque but spring force as well. There are some, but they don't go too large.
You can get battery backup for electric actuators, but you better have adequate back up power to drive it home. Batteries require maintenance and you generally don't stroke it but once.
rmw
(Electrical)
26 Jun 11 21:26Look for pinch valves, Larox is one manufacturer. We've used them on sea water at pretty high pressures. They'll even seal well with shellfish in the seat, and some larger fish too.
Several other manufacturers out there.
Good on ya,
Goober Dave
(Electrical)
26 Jun 11 21:27Forgot to mention, you can get internal combustion actuators too -- so all you have to maintain is a starting battery.
Goober Dave
(Mechanical)
26 Jun 11 23:17Use a Rotork & Auma electric actuator.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
(Mechanical)
27 Jun 11 08:18All above are relevant comments in my opinion for actuation and valve selection.Two informations ought perhaps to be evaluated before final solution is selected, and some details in addition to be clarified:1. What is the actual required operation pressure? Note: if this is intake point the real pressure could be lower and a PN150 knife gate could possibly be selected. (A 300psi class knife-gate is not impossible but price and availabillity could be an issue)2. If the valve is placed further downstream some sort of filter or screening is normally done further upstrea at intake point (for instance motor or handwheel operated in beltform screen to be easily cleaned, and possibly a second filter in addition to protect the pipeline components further downstream).If there is alimitation to amount and size of debris, double eccentric flanged butterfly could be evaluated. This system is commonly used for river-intake for hydroelectrical power plants.3. Frostfree? If yes pneumatics might be evaluated for piston-type actuators in stead of spring return, with failsafe solenoid pneumatic valve and mini-compressor refilling if necessary suitable small reservoir.4. Mostly used in Scandinavia at remote locations are gearing and multiturn electrical actuators (both Auma and Rotork and others have suitable sizes gearing and small (limited watt) motors. Motors ought to be dimensioned after longest possible shutdown time to keeep motor-size down. Can be given a two-step speed closing if steering/signals are selected with correct components.UPS (battery-backed) 24V DC or 240/60 (240/50 in Europe) AC single phase are mostly used for theese systems. Other currents available.I would personally have gone for a top-quality knife-gate (dropthigt at least at 150lbs both directions)if lower pressure, and BFL double eccentric, top quality, flanged with suitable gearing if higher pressure and somewhat debris protected.If debris still is the main issue a pinch-valve is not a bad solution, but will cost a bit more in my opinion. Also high-quality is required for this solution, low quality will sooner require change of the valve rubber/elastomer body.After importance: test-run of solution should be done 4 to 12 times a year. In addition : Greasing necessary if knife-gate solutions ( one time a year?).
(Electrical)
2 Jul 11 22:23Consider longer term cost in addition to initial purchase cost. Consider quarter turn valves if possible. Perhaps that does not suggest that automated gate valves are not worth any consideration; perhaps others might. The pneumatic solutions are good for quarter turn valves. Higher turn valves suggests gate valves with no failure position even on UPS power.
(Civil/Environmental)
6 Jul 11 14:25A gate valve is NOT always a multi-turn valve. Google "cylinder operated gate valve" or "hydraulically operated gate valve". I have used both air and water operated, and have replaced both kinds. Water is good if city water or stored, pressurized water (elevated) is available. Most water cylinders are chrome plated, and at thirty years look pretty bad. Most air cylinders are stainless, but the air supply can be a maintenance item. I have used rubber pinch valves (Red Valve) with water, air or guillotine operator and prefer the resilient seated gate valve.
Steve
(Mechanical)
13 Jul 11 04:13metal seated
triple offset (butterfly) valves too. Depending on the type of debris and on the possible orientation, they could also seat and operate better than ball valves... moreover, they may result lighter and require smaller actuators (as the main torque requirements arise near the fully closed position only, remaining negligible along the rest of the 90° opening and closing strokes).vehazle,about the quarter turn solutions You examined: may be You could considertriple offset (butterfly) valves too. Depending on the type of debris and on the possible orientation, they could also seat and operate better than ball valves... moreover, they may result lighter and require smaller actuators (as the main torque requirements arise near the fully closed position only, remaining negligible along the rest of the 90° opening and closing strokes).Of course, in the end You should compare the total costs of each type of actuated valve package...Hope this helps,_______________________________
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