Micromotion, negative flow

[mayeyi]

I have a 2700 micromotion xmtr (Foundation Fieldbus) with a T series sensor. The problem is that I need to cut-off the negative readings (Reversed Flow) so it won't affect the process batch station totalizer when the process start. How can I program the Transducer and/or AI1 block so my Delta V system does get those negative reading from the xmtr. Using my 375 communicator I can't program a density cut-off. Any help!

 

[jmw]

This is the sort of thing MicroMotion can answer over the phone.
It ought also to be in the manual.
I can see why you might want a low flow cutoff value but only if this is due to false flow readings and not due to a leaking shutoff valve.

You might also get flow readings after shutoff if all you do is shut down a cenrtifugal pump without a valve. In this case you may get reverse flow if the system can drain back down through the pump or forward flow if it can continue to flow forward for a period due to inertia or some other cause.

Before making adjustments to program settings, be sure the the installation is good. You don't necessarily need a shut-off with a centrifugal pump, a spring check valve might prevent reverse flow or forward flow without pump pressure behind it.

I'm unsure why you need a density cut-off. Even with no flow you will have a density value for the fluid in the tubes.


JMW

http://www.ViscoAnalyser.com

 

[Ashereng]

Hi mayeyi,

Have you tried to to clamp the reading of the input in the Delta V?

The input function block in the Delta V should have a clamping feature.

This way, the micromotion is free to indicate what it measures, and the Delta V is ony totalizing 0's.

ashereng

 

[jsummerfield]

The milliamp units also have an alarm output in the "C" output. Perhaps that signal value can be used to clamp the measurement signal or to provide an out of range alarm in the fieldbus units.

Push the Micro Motion types to help think of a way to get what you want. Most sales folks are done once they get the PO. However, some factory nut may know just about everything that can be done via the 2700 with fieldbus.

John