I need a "Flow Switch"
I need a "Flow Switch"
(OP)
Hello all,
I am looking for a method to determine whether fluid (most probably water) is flowing/being pumped from a remote location. Perhaps a switch or sensor that activates a current once flow is detected.
It needs to be
-small
-inexpensive
-withstand about 2000psi
Perhaps someone can point me in the right direction, I have heard the term "flow switch" tossed around, but is it viable, and are there any other options?
Thank you,
Ras
I am looking for a method to determine whether fluid (most probably water) is flowing/being pumped from a remote location. Perhaps a switch or sensor that activates a current once flow is detected.
It needs to be
-small
-inexpensive
-withstand about 2000psi
Perhaps someone can point me in the right direction, I have heard the term "flow switch" tossed around, but is it viable, and are there any other options?
Thank you,
Ras





RE: I need a "Flow Switch"
A flow switch, by itself, isn't going to do the job. Think about the project a little and determine if you need to know if fluid is actually flowing or if it's sufficient to know that a pump has started or a valve has opened. If it's the former, you need something that actually measures flow not just voltage. If it's the latter, than why the 2000 psi? Look at Crane's Technical Paper 210 "Flow of Fluid" - at the very beginning they have a discussion on flow measurement.
Patricia Lougheed
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RE: I need a "Flow Switch"
This is for a groundwater monitoring application. It will not suffice to know whether the pump is working. The chamber will be filled with fluid and not always pumping. For controls sake, it is necessary to have a sensor to determine whether the fluid is being pumped, regardless of whether the pump is working or not. The fluid could be as high as 2000psi, however, there is no need to know the flow rate, only whether there is flow or not.
Thank you
RE: I need a "Flow Switch"
Check with Kobold for their PSR paddle type flow switch. the ss units are rated at 3600 psig @ 230F.
Hope this helps.
saxon
RE: I need a "Flow Switch"
All of the above is assuming a reasonable sized pump/motor for the application (not grossly oversized). If it is oversized it will be more difficult to differentiate between adequate flow and not adequate. It can still be done.
I would definately handle it with monitoring the power. All of the actual flow meters/switches I have seen are a lot more expensive and a lot harder to install. Good luck.
RE: I need a "Flow Switch"
But on a one-off situation this is a great way.
We have had a serious problem with flow switches for many years. In the last year we negotiated a custom made flow switch using thermal dispersion. No moving parts, highly accurate, highly repeatable, and our tests reveal what we thought, high reliability because we adapted it from the steel mill industry where electric is nasty.
Not many companies make thermal dispersion flow switches, therefore hard to get. Let me know if you are interested and I will give you contacts or sell you one of ours.
Reason we left the paddle types is that they are unreliable, hard to install properly, do not last very long.
PUMPDESIGNER
RE: I need a "Flow Switch"
I would like to have a look at some literature on theses thermal dispersion flow switches.
I am working within a budget, as well as space restrictions(as I am sure we all are at most times), and this will play a big part in determining the feasability of these switches.
Thank you very much for your help.
Ras
RE: I need a "Flow Switch"
http://www.dwyer-inst.com/
http://www.captor.com/
http://www.ifmefector.com/ifmus/web/home.htm
Captor is the best one of the bunch.
Problem with all of them is that they are for small pipe only because of the industries they serve. Which is why we had to have a custom.
The Dwyer link also has mechanical paddle types.
PUMPDESIGNER
RE: I need a "Flow Switch"
Are there any web sites that talk about motor power as it relates to different pumps under dry running conditions?
RE: I need a "Flow Switch"
Franklin has their own little dohicky that attempts to determine that the pump is either dry or running at dead head based on current, but they explain nothing about the dohicky except to say that it is current based and only applies to their submersible motors. That dohicky I'm sure is a big problem to them if someone couples the Franklin motor to a high Ns value pump where the current relationship is reverse from a low value Ns pump.
PUMPDESIGNER
RE: I need a "Flow Switch"
What sorts of applications (or pump types) would the relationship be reverse?
RE: I need a "Flow Switch"
Propeller pumps draw more energy as flow is reduced. Centrifugal pumps draw less energy as flow is reduced.
Mixed Flow and Fancis Vane pumps (mid range Ns) are as you might expect, everywhere between the two extremes.
Hard to tell by looking at exterior of many pumps, actual Ns calculation has to be done. But suffice to say that there are many, many pumps on the market that look just like a centrifugal that are high Ns value pumps with current/flow relationship reverse of what you might think.
Pumps used to supply potable water to a home, or run a small sprinkler system are low Ns centrifugal pumps. Many pumps working on chillers, water features, or cooling towers have High Ns values.
PUMPDESIGNER