Reasons for fluctuations in steam flow meters
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Our company has a high-pressure steam flow meter used for settling accounts with the steam supply company. The basic specifications are as follows: Pressure sensing element: Rosemount flow nozzle; Transmitter: Rosemount 1151 intelligent differential pressure transmitter, along with Rosemount intelligent temperature and pressure transmitters； Accumulator: Rosy Accumulator. Fluctuation phenomenon: The traffic trend chart often shows significant swings, yet the cause of these fluctuations cannot be identified. Since our company’s production is relatively limited, the steam consumption should remain constant when the load is stable. During the fluctuations, the shift supervisor said that the load was very stable and no adjustments were needed. Moreover, the trends in steam temperature and pressure appear to be relatively stable, with the pressure sometimes fluctuating by about 1 kg ； Superheated steam set by the accumulator. Based on the pressure and temperature of the supplied steam, it remains within the range of superheated steam and does not drop below the supersaturated level. Checking the flow differential pressure transmitter – good. However, the steam flow still experiences significant fluctuations from time to time; this problem has been bothering me for a long time, and I hope I can get some valuable advice from everyone.
Is it possible that the instrumentation staff activated the differential pressure transmitter before allowing the condensate to fill the ducts after performing maintenance on it? It is best not to perform maintenance on differential pressure transmitters used for measuring steam.
Thank you for your reply. A condenser is installed at the outlet of the pressure tapping pipeline. And the fluctuations occur during normal use, so that can’t be the reason.
1 Check whether the pressure guiding tube is leaking. 2 Re-calibrate the differential pressure transmitter. 3 Inspect the pressure sensing element nozzle
Check for any damage on the signal lines, for any sources of interference, and also check whether there are any sources of interference at the location where the meter is installed
If there is nothing wrong with the instruments, then one should consider whether the pressure lead pipes of the differential pressure transmitter are blocked or if there are issues related to the heating of these pipes. If the heating pipes are too close to the pressure lead pipes, it may cause errors in differential pressure measurement. We have encountered such problems before, so we’re providing this information as a reference for you
I think it’s caused by line interference; locate the source of the interference and implement proper shielding.
It would be best to take measurements of the pressure gauge output under conditions of fluctuating flow, to check whether the output value matches the displayed value； By the way, it’s possible to check whether there is debris inside the nozzle, and whether the steam pipes are rusty.
First, please let me know whether the transmitter outputs pulses or 4-20mA.
All have a output of 4-20 milliamps
If the blockage of the pressure tap is ruled out, the most likely cause is a problem with the root valve; I’m not sure what type of valve it is
Oh, I hadn’t noticed that. Thank you for the reminder.
Is it related to the type of root valve? Explanation.