3051S DP Transmitter Fluctuating

The Hart DP seems to be taking the air density into account by a different calculation....these two transmitters may not be programmed the same...

http://www.validyne.com/blog/application-note-basics-of-air-velocity-pressure-and-flow/

The [Honeywell] 3051 is part of a family of differential pressure transmitters. If connected correctly, the instrument will measure the differential pressure across some sort of restriction in the flow, and <...during normal operation both reading 8000kg/h...> suggests that some sort of algorithm is in use within the instrument to infer flowrate from differential pressure.

<...Air blower...> suggests that the measurement is of pressures slightly above atmospheric.

It ought to be possible and practicable to chase-round the <...instrument tubing..> looking for leaks, particularly if only 1 instrument of the 2 is suspect. If a proprietary leak testing fluid is unavailable, one might use water with a healthy dose of common washing-up liquid in it as the leak will manifest itself as bubbles, which are easily seen. Once found, the remedial action depends upon the nature and the location of the leak.

At these sorts of pressures, a simple kink in the tubing may result in a leak, which the instrument can measure and which cannot be seen or heard above the background din from the <...blower...>. It is likely that any leak will be found on the low pressure side of the suspect transmitter and fairly close to it.

Come back to the forum after this investigation is completed, please.

<subscribes>

the low pressure side the high pressure side

Check and verify the calibration of both transmitters.Here is a link:

https://blog.beamex.com/2016/01/26/calibration-of-a-hart-transmitter-and-the-most-common-misconceptions-about-the-hart-communicator

• If leak elimination doesn't work, the next step is swapping the instruments physically between the two locations, to see if the fault travels with the instrument or remains with the pipework.
• If the problem travels with the transmitter, try changing-out the suspect transmitter for the stock spare, and try again. It is unlikely to be a similar fault with two transmitters.
• If that doesn't work then it's a detailed phone call or two with the transmitter supplier and/or manufacturer.

Please come back to the forum once those things are completed.

<remains subscribed>

Hi,

Thanks for joining discussion about this topic,

Calibration range is 0-100mmh20 for both transmitter and as of primary suspect

HART transmitter just replaced 1 month back ,still behavior is same,

Tubing inspected - no leak - parameter matched for both transmitter - heat exposer parts covered.

...then it seems a telephone discussion with the supplier is the best route to a solution.

<unsubscribes>

Try swapping the tubing taps to the transmitters if possible.Are the tubes simply joined at a TEE,or a manifold? Could be a restriction in one port getting smaller as temp increases.

It's connected at TEE,

we may try your option swapping tube but, one thing here I like to share is It starts deviating since noon Temperature rise so now may I need to look this also,

Regarding the possibility that the HART transmitter might be reading correctly rather than the FF transmitter, I've experienced that a couple of times except my experience was with temperature sensors (thermocouples). The operators believed the first sensor was correct and complained that the second sensor was defective. A check revealed that the second sensor was good and the first one was defective. Sometimes it's the reading we want to see that seems normal.

A comparison and analysis of the transmitter's parameters might be in order as well as an inspection of the impulse tubing.

Confucius say:"Man with two watches never knows what time it is."