vortex transmitter

I have rosemount flow transmitter type 8800D vortex with the following data: URV:850 and LRV:0 bbl/d and shedding freq. @ URV : 676.088,k-factor:1636.2461,low flow cutoff(lfc):341.6 and min lfc: 35 .
The problem that there is flow passes through pipe and no flow reading at transmitter but it works at past properly i make some steps to investigate problem:
1-electronics verification with flow simulation and the test is ok.
2-change lfc for different values but no effect.
The transmitter don't sense the flow till the flow reaches 40% so i want to decrease it to 20% what can i do
And i have another transmitter reads values and there is no flow what i can do?

Vortex shedding flow transmitters are very high tech devices. I suspect almost everything about them is proprietary. This is probably a case where the factory or supplier should be contacted for assistance. It appears you have done the checks that can be reasonably performed by a non-specialist.

Have you cleaned it?

1) You should be aware that ALL Vortex meters have a configurable low flow cutoff AND a non-configurable low flow cutoff. The non-configurable low flow cutoff is the point at which the flow velocity is too low to generate a sufficient number of vortices for the meter to get a good reading, so the meter says "zero flow". The drop-off at the low end, shown on the graph below, is from sizing software for a different brand vortex meter.

The flow rate might be in the non-configurable low flow cutoff range - if the line size is too large to get a high enough velocity.

The graph is from a vortex sizing program, showing the range over which the vortex meter will operate.

Note that the flow rate on the X axis does NOT go to zero.

The lowest flow rate for the design conditions give a minimum flow at 15.2 gpm (not your case, but for another situation)

This is the non-configurable low flow cut-off point.



2) When the meter worked in the past, was it with the same fluid? Vortex meters don't like thick, viscous fluids.

3) Fluids that can polymerize (degrade and form scum goop) can prevent the sensor diaphragm from flexing, which is what Mickey is referring to - sometimes the sensing elements need to be VERY GENTLY cleaned. It's easy to damage the sensors, so GENTLE is the key word when cleaning a vortex bluff body sensor.

4) All Rosemount manuals have a troubleshooting section. Have you read through that?

Thanks for help and i read rosemount troubleshooting but i am not cleaning bluff body i will try it