Reverse flow alarm using Ultrasonic flow meter

D

Thread Starter

dasa

Hi
We have an application where it we need to measure liquid flow using ultrasonic flow meter.

Since we are connecting to a common discharge header where other users also connected there is a possibility of reverse flow, we have all protection like NRV in place.

Our Client requires, only an alarm to be configured when any reverse flow is detected.

Flow meter powered by 24 VDC and we are taking 4-20 mA only from meter to control room.

We are thinking to ask vendor to provide an alarm contact in the flow meter which is to be configured for reverse flow.

Is there any other techniques we can use to detect reverse flow?

Regards
Dasa
 
N

Namatimangan08

I assume you have "Time-in-Transit" ultrasonic flow meter. I think it d works equally with a "Doppler Shift" type.

If such reverse flow causes your client's liquid flow to reverse then you can configure the transmitters. The one that normally transmit acoustic signal against the flow of the liquid will be used to transmit the wave with the flow. The one that normally used to transmit acoustic wave with the flow will be used to transmit the wave against the flow.

From theoretical point ultrasonic equipment shall able to provide readings for both directions of fluid flow. Unless the logic calculation assumes negative delta t (Time in transit with the flow-time in transit against the flow as a noise signal. In this case you will not able to read the flow in normal direction. Only the flow in reverse direction will be calculated.

Just in case the piping configuration is more complex, think about using many flow meters to be placed at many suitable locations. The basis of the measurement is done based mass balance.
 
S

Scharf Automation

Absolutely right. There is an alarm output on flow meters to detect the direction of flow.

We provide the same in Electro-magnetic flow meters but not sure whether you would get the same in ultrasonic type of flow meters.

The other to work around with this issue is to have a flow switch installed in the pipe line to get the direction of flow.

The flow switch operates only in one direction so that you can connect it in reverse direction. So when the flow is reversed, it would be activated.

Regards,
Sarfaraz
 
Dasa,

If you are open to other options besides the ultrasonic flow meter, then my company has a very clean solution.

We manufacture the EtherMeter, which is a device which connects to many turbine-type flow meters and converts the readings into Modbus. When the turbine turns in one direction, the reported flow rate is positive, and when the turbine turns in the other direction, the reported flow rate is negative.

The EtherMeter also provides distinct Modbus bit-flags that correspond to forward and reverse flow detections, and these can be tied directly to your alarm logic.

If that's not an option, I liked Sarfaraz's suggestion to install a flow-switch.

Hope this helps!

-Jim.
 
Hi Dasa,

I am not sure what Brand ultrasonic flow meter you have used. But usually ultrasonic flow meter has a alarm function for some item,e.g. Reverse flow alarm.

For more information, you may visit the website: www.ultrasonic-flow.com

Bill
 
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