Flow Transmitter/Switch Problem


Thread Starter

Evil Genius

We have Rosemount Vortex Flow Transmitter (Model 8800C) installed at water line. This line contains Dematerialize Water (0.5 µs) & Sea Water (60,000µs) - both type of water is passed through this line in different scenarios.

Minimum flow present in this line is: 1m3/hr.
Minimum Pressure present in this line is: 1.5 Kg/cm2

Upstream Line Dia = 2"
Downstream Line Dia = 1.5"

LRV & URV Settings of this Vortex Flow transmitter is: 0 m3/h & 5m3/h.

The major problem is, Transmitters take a lot of time to grasp the reading once the line gets empty & refill. Also sometimes transmitter get Saturated at 105% or at 45% etc. etc irrespective the flow is present or not. Moreover We have 08 transmitters installed on 8 different pumps in same fashion for the same purpose & these problems are being faced on all transmitters.

Can you please suggest root cause of these transmitters problem?

We have already checked Float Type Switch, Turbine type (rota) flow meter but both did not get successful. In Float Type Switch, sea water salts deposited on the floating mechanism. In turbine type flow meter, its rotor often got broken.

Also please suggest any alternate type of flow detecting instrument….
Which type of flow switch would work for our application (considering Demin & Sea water presence + flow rate).

<b> Mods note: Demin = diameter?</b>

Any suitable type of Flow switch instead of transmitter would also work for our application as we just need to detect the presence of flow.

Bob Peterson

have you considered discussing this with the people that sold you the equipment?

vortex meters are pretty bullet proof for simple applications like this.

the thing is that if there is trapped air in the line, a vortex meter is going to have issues with that.

as for your reading being saturated, i am guessing you mean the reading is stuck at some value. this could be all kinds of problems. is this what is being displayed on your control system or what the meter itself is displaying? it might be that when the meter is full of air it goes to some default value like 3.5 mA and your control system is seeing that as a fault so is staying with the last known good value.

if problem is because of air in the line as u say. then make a u shape line to avoid the air for meter & installed the meter in center. length of bend should be as straight as required for meter.
In my experience you won't get anything more reliable than a vortex flowmeter, the ones you have are as good as any.

I suspect when the meter gets "stuck" it's caused by pipeline vibration.
Take a good look at the installation and installation recommendations, straight run requirements etc, I'm sure you will find something wrong there.

Flow switches are unreliable, I have yet to find one I would trust.