ABB DP with pitot sensor not reading flow correctly

Hi everybody I have ABB DP Flow transmitter with pitot sensor not reading flow correctly we have 4 type line this with every block 1,2,3,4 instrument 2,3,4 are reading same flow but the for block 1 instrument reading much higher and fluctuating to much and reading are much higher than the remaining 3 Flow transmitter.This FT have the same range and configuration .
1. Presumably you have a manifold valve between each pitot tube and its DP transmitter.

Swap/exchange one of the three good-working transmitters with the bad boy transmitter.

If the problem moves to a former working-good location, then there's an issue with the transmitter.
If the problem remains the same, then it is not a transmitter issue, it is a manifold valve/impulse tubing/pitot tube/application issue.

2. Several reasons why a DP flow transmitter can read high are

- DP xmtr configured to the wrong range, for example 0-2.50"wc range, not 0-25.0"wc.

Don't believe that the configuration is identical until you have witnessed yourself. I know of cases where someone sitting at a desk using an asset manager changed the parameters on the wrong tag transmitter. It happens. Connect a communicator to the bad boy and one of the others and compare the settings.

- 3/5 valve manifold low side valve/passage is blocked (scale, crud) or not opened, xmtr sees only high side pressure

- Low side impulse tube/port crimped/clogged closed, xmtr sees only high side pressure

- somewhere, the low side is leaking to atmosphere

- Gas application, Xmtr mounted beneath the pipe, high side impulse tube filled with liquid causing it to read high,

- high side impulse tubing drip leg has not been drained and is 'overflowing' into the high side impulse tube

- Double square root – square root done in the xmtr and in the receiver/HMI/DCS