Hi, we are using Vortex flow meter of Emerson Make in Syn gas flow line in ammonia plant. Flow meter measuring range is 0-30000 Nm3/Hr. Normal flow rate is 23000 nm3/hr. We observed that flow meter reading having fluctuation up to 1000-1500 Nm3/Hr in normal running condition. This flow meter is having remote mounted transmitter. We changed sensor, its cable up to transmitter but still have variation in flow. As per process, there is not fluctuation in syn gas flow.
please guide what to check further to resolve problem.

 

Sometimes good instrumentation shows a process condition that operators don't want to see. How do you know that " there is not fluctuation in syn gas flow"?

Noise can be the result of a poor flow profile. Swirls in the flow profile affect the formation of vortices. Vortex meters need long upstream and downstream straight runs to guarantee a reasonable flow profile; lack of straight run can cause oscillation/noise. A misaligned gasket can cause swirls that affect the profile, as can misalignment of reducer fittings. An upstream control valve is a no-no.

Pipe vibration can also cause a noisy flow rate signal.

Most Vortex flow meters can be checked with a sine wave frequency generator and an oscilloscope to 'prove' the electronics are functioning correctly.

 

Your vendor provides flow meter calculations, showing the range of fluid velocities, and expected accuracy levels.
you might summarize the data they provided, currently you are experiencing 4-6% fluctuations, relative to normal flow.