On-site repair of metal tube float flowmeters

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I haven’t been to the Haichuan Chemicals Forum for a long time; I came back to check it out recently. Recently, a customer at the Tianjin site reported that a metal tube float flow meter was exhibiting abnormal current signal output; the LCD display of the instrument at the site worked normally. Even after it was sent back to the factory for repair, the issue remained unresolved. Upon arriving at the site, the on-site staff explained that the instrument showed over 70% normal operation on the DCS; even when the valve was closed, it could not return to zero on the DCS, and there was still a flow rate of 60%. It has not functioned properly since it was installed. During the on-site inspection, after the valve connected to the instrument was closed, both the pointer and the LCD screen showed a reading of zero. A multimeter was used to measure the current in the circuit, which was 13.6 mA. The on-site instrument indicated that the issue was caused by a fault in its own circuit board. The power supply at the site was disconnected, and the instrument was used to supply power; the circuit current was normal. It is therefore determined that the issue lies with the on-site power supply. Upon arriving at the control room, the instrument at that location was connected to a normal display terminal, but the fault persisted; it was determined that there was no issue with the power supply. The cable’s insulation strength was tested using a megohmmeter; the resistance between the positive terminal and ground was very low, but this could not be detected with a multimeter. Based on this, it was determined that the insulation of the wiring was poor.