Analysis of the reasons for sudden changes in V-cone flowmeters measuring steam flow
Thread Content
The V-cone flow meter used for measuring steam showed a normal reading of 40 tons; however, it suddenly dropped to 20 tons and remained at that level for 15 seconds before dropping to 6 tons. A few seconds later, it returned to its normal value of around 40 tons. Analysis: The reading had been stable up until then. There are no issues with the wiring, insulation or heating systems, the transmitter is functioning properly, and there should be no problems with the pressure tapping pipes either (since the environment remains unchanged). The shielding cables should also not cause any interference. What other possible causes could there be?
Additional question: Is it the transmitter’s instability that causes the approximately 30-second delay between the start and end of the process? On the control room side of the shielded cable, is it possible for ground interference signals to still get in? Shouldn’t there be any signs of gas-liquid mixing in the pressure tap tube as well?
Have there been any changes in the temperature and pressure used for compensation?
Reply to 3# wlb409: This circuit does not have temperature and pressure compensation; it features a transmitter with one input and two outputs, and flow rates experience fluctuations in both SIS and DCS systems. The duration of these fluctuations is around 30 seconds. Could it be due to issues with the pressure sensing tubes or external interference?
The interference issue should be resolved by grounding the instrument separately!
Regarding the heat tracing issue, try turning it off
Reply to 3# wlb409: If it’s a problem with the pressure tapping pipe or heating system, why were there no signs of it beforehand? As for interference, use shielding cables and ensure proper grounding in the control room
I just checked the connection between the cable protection tube and the tray, and found that the cable’s insulation layer was severely damaged; there may be multiple grounding points in the shielding layer as well