The previous article talked about two common malfunctions and solutions of knife gate valve. This article will explain the remaining two. Let's have a look!

3. Ineffective Lifting of Knife Gate Valve Stem

(1) Cause of Ineffective Lifting

① Excessive operation causes thread damage;

② Lack of lubricant or lubricant is invalid;

③ The valve stem is bent;

④ Insufficient surface finish;

⑤ The valve stem nut is inclined;

⑥ Improper material selection;

⑦ The open-air valve is lack of protection, the valve rod thread is covered with dust and sand, or corroded by rain, dew, frost, snow, etc.

 (2) Solutions

① Careful operation, do not use force when closing;

② Check the lubrication condition frequently and maintain a normal lubrication state;

③ Do not open or close the valve with a long lever to prevent the valve stem from being twisted;

④ Improve the processing or repair quality to meet the specification requirements;

⑤ The material should be corrosion-resistant and adapt to the working temperature and other working conditions;

⑥ The nut of the valve rod should not be made of the same material as the valve rod;

⑦ When plastic is used as the valve stem nut, the strength should be checked, the corrosion resistance and friction coefficient should not be considered only;

⑧ Open-air valves should be provided with valve stem protective sleeve;

⑨ For frequently opened valves, the handwheel should be rotated regularly to prevent the valve stem from rusting.

4. Other Malfunctions and Solutions

① Valve body cracking: It is generally caused by freezing (This situation is generally caused by improper material selection, the valve material is not resistant to low temperature). If low temperature resistant material is selected, thermal insulation measures should be taken for the valve body;

② Hand wheel damage: Due to impact or heavy operation of long lever. It can be avoided as long as the operator or other relevant personnel pay attention to it;

③ Filler gland fracture: Uneven force when pressing the filler, or the gland is defective. When pressing the filler, the screws should be rotated symmetrically without deflection;

④ Failure of connection between valve rod and ram: Solve it in terms of manufacturing.