Flow Switch

• What is in the line, its temperature and pressure?
• What is the size and materials-of-construction of the line?
• Is the line horizontal, vertical or what?
• The high fluctuations - is this a 2- or 3-phase mixture?
• What is the intended use of this "flowswitch"?
• Would "de-bouncing" in software be an acceptable technique?
• etc.

With the low price and flexibility of todays Mag meters you may find that they may address your needs....That is if your fluid is conductive....

Can you offer any of flow parameters?

Hi

Flow is Demin water with 4 Barg pressure and 20 degree C temprature.

Material of pipe is stainless steel and diameter of pipe is 10 inch.

vertical and horizontal piping both are available. but maximum straight horizontal vector is 1.5 meter.

Best regards!

Do you have a feel for the water's conductivity?

200 ohm/m

That's seawater diluted by a factor of 10 or so, not demin! Double-check the units, please, and re-post.

Why is the flow fluctuating?

What is the set point of the "flowswitch"?

What is the intended use of the "flowswitch"?

In fact, turbulency is the main problem.

so that i said before, maximum straight horizontal path in the system is 1.5 meter wheras the pipe section is 25 cm. and its the reason of turbulency.

can i use a calorimetric flow switch in a vertical line?

Generally, yes.

Thermal dispersion flow switches tend to work well with low temperature media. All claim to be temperature compensated, some better than others, but be aware that step changes in temperature are likely to cause false trips. Drifting changes in temperature can be handled pretty well.

Also, this technology tends to be VERY good for low flow measurement, but does have a upper flow range limit (which is not at all unreasonable), so check to make sure that your flow rate for your line size insertion point does not exceed the flow maximum that the device can handle.

Some of them do cyclic readings with a 5-6 second cycle time. Hence, a response is time limited to the cycle time, unlike a sail switch which responds nearly instantaneously to flow changes. But in turbulent flow that seems to have been a problem for you, so a cyclic response might work to your advantage.

I saw one model that offered a continuous flow measurement and a switched output, which might be of value.

<...said before...>

It is what hasn't been said that remains of interest!

Turbulence and fluctuation are two different things.

• Turbulent flow in pipes is if the Reynolds Number is over about 2300. All flowswitches can operate in turbulent flow. Virtually any water flow in a 25cm Ø pipe will be above this figure.
• Fluctuation implies the flowrate is varying greatly over a short timescale. So, again, what is this flowswitch supposed to be doing in a greatly fluctuationg flowrate? And if the flowrate is varying so greatly, why is this happening, what is the switch supposed to be operating, and what is the meaning between the one state of its output and the other state?

It has been some time since these questions have been asked, and without meaningful answers to them the discussion cannot move forwards to an acceptably focussed solution!

Hi PWSlack

before continue discussion, please answer this question:

why in all of instruction manual of flow switches it is mentioned that 5 DN before and after place of flow switch its necessary that no bending ,pumps,etc must be there?

i think its because of turbulence but you believe, in a line with 25Cm Ø there is no turbulence.

Best regards!

If you do indeed have an issue with upstream flow turbulance put in a flow conditioner upstream. FCI who makes the thermal swithes makes a flow conditioner. If you contact them they can make recommendations for you applciation.

Another way to go is to install an orifce plate in the line with a DP indicator with a switch. That way you can measure your flow an set the flow switch at the desired set point.