The butterfly valve is generally less than 90 ° from full opening to full closing, and the butterfly valve and butterfly stem have no self-locking capacity. In order to position the butterfly plate, a worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make the butterfly plate have self-locking ability, make the butterfly plate stop at any position, but also improve the operating performance of the valve.

4. Investigate item 4 in the flow chart of liquid physical property checking. When the conductivity of liquid changes or is uneven, the zero point will change when it is stationary, and the output will shake when it flows. Therefore, the flowmeter should be located far away from the injection point or downstream of the chemical reaction section of the pipeline, and the flow sensor should preferably be installed upstream of these places. If the liquid contains solid phase, or impurities deposit on the inner wall of the measuring tube, or scale on the inner wall of the measuring tube, or the electrode is polluted by grease, etc., zero point change may occur. Because the scaling on the inner wall surface and the degree of electrode pollution cannot be completely similar and symmetrical, the balance set by the plant's initial withering will be destroyed. Active measures should be taken to remove dirt and scale deposits; If the zero partner changes little, you can also try to reset it.