Pump Control Valves 3

[simoneaux]

I am looking for a comparison of the types of pump control valves. I am interested in the pros and cons of electrical, pnuematic, and hydraulic control of valves used downstream of pumps to check flow and prevent pressure surges.

 

[stanier]

Pumping Handbook by Karassik

 

[Cvguy]

Here's a hydraulic version.

http://www.cla-val.com/pdfs/Animation-60-11.exe

Pros: Generally best for surge protection with built-in check valve. These valves also have adjustable opening and closing speed controls.

Con: More pressure drop than actuated ball or butterfly valves.

 

[semo]

We've used three types of valves for automatic valves and had good/bad experiences with all.

Electric valves only work when power is on. If you lose power when the pump is running and the valve is open, the valve will stay open when the pump quits running. These valves don't typically open as quickly as the other two can. You don't want the valve to open quickly on a pump control valve though.

Pneumatic valves require a compressor to operate. The air supply must also be dry and of good quality so the compressor needs a dryer and filter. These valves also use electric actuators; but, if power fails, the compressor typically has enough air storage to operate the valve and close it as the pump shuts down. We've had problems with some of these valves fluttering when we reduced the operating speed.

Hydraulic valves use the water pressure that is already being provided by your distribution system. These valves also use electric actuators and can close upon power failure. We recently have had some difficulties with the bronze actuators de-zincifying from the water supply and leaking.

I don't know that one is better than the other when it comes down to it. Alot has to do with client preferences.

 

[gustorf]

The european style is to install a Noreva nozzle check valve on the discharge of the pump to prevent backflow surges followed by a simple electrical operated butterfly valve for pump start-up and close control.
-Easy to handle and maintain, safe at power failure, low pressure losses.

 

[stanier]

gustorf,

That is what is being employed for three 2500kw pumps serving a DN3000 water supply to Sydney as well as other water projects in Asutralia. As last we are seeing good European technology downunder. All the USa has to do is play catch up.

 

[bimr]

As Noreva's website notes, non-return valves has been represented on the world market for over 70 years. Would that would mean that non-return valves are a 1930's technology? Seems like everyone in the world should have caught up with that technology by now except those that are a snag short of a barbie. There is also a company in the USa that has been selling these things for years:

http://www.valmatic.com/checkvalves.jsp

The pros and cons of electrical, pnuematic, and hydraulic control of valves depend on the application, water distribution system, mode of electrical failure, type of pump controller, the pumping head, elevations and flow capacities of the application as well as user preference. In this case, there is no one size that fits all.

You need to start with with a stress analysis of the proposed application. Then talk to a supplier such as Henry Pratt or GA Industries who supply all of these components.

 

[stanier]

Its amazing how few have managed to keep pace with technology. Not only for check valves but also for air release/vacuum valves.

It appears to be a bury your head in the sand approach. Few engineers actually model their piping systems for dynamic loads. The tools are there but they choose to ignore the fundamentals. Check out the following quote and find that their knowledge is indeed meagre!

“In physical science the first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science, whatever the matter may be."
Lord Kelvin [PLA, 1883-05-03]”

 

[gustorf]

Let me just point out that the Noreva valves are well known in the american and canadian oil and gas industry.
Its only the water market that was protected by "buy american" clauses for decades.
If anybody wants some actual references about the performance of these valves compared to so called "silent check valves" of Valmatic or APCO which are NO nozzle check valves, just contact the manufacturer.
You may also want to get a dynamic behaviour calculation for your specific reverse flow acceleration, the closing time and max. pressure increase (surge).
Or you may prefer an energy cost comparison of different valve types.

 

[stanier]

Gustorf,

Its very difficult to break into fortress america! Thats why the French and British water companies and consultants dominate this market world wide. American companies can only get in by acquisistion or with financial hooks into the scheme.

 

[bimr]

stanier,

The global corporation ends up paying the same cost to send 2-3 Brits overseas as it costs for 1 American with taxes. What would you do?

Sorry to disappoint you, but the reason is for taxes, not technology.