What to do if a gate valve is rusting
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The gate valve used by the company has not been in use for a long time and has rusted shut; it is likely that there are debris or rust between the upper gland and the valve stem. Given the complexity of the material handling process, is there any way to resolve this issue without replacing the valve?
Loosen the screw that holds it in place, apply rust remover to it for a while – this should make it possible to turn the valve stem. However, if a gate valve is not used for an extended period of time, the gate inside it and the valve stem may come loose during rotation (get stuck inside), and just because it can be opened does not mean the valve is in good condition. I have no choice but to give it a try.
For gate valves that have not been used for a long time, the most obvious symptom is that it is difficult to turn the handwheel, with a significant increase in torque. Online, it is possible to first add lubricant using rust remover, or isolate the valve and remove the handwheel mechanism; then loosen the welding fixing ring, take out the shaft sleeve, and carry out cleaning.
First, it is necessary to determine whether the material is a hazardous chemical, the load exerted on the valve while it is in use, and the position at which the valve is opened or closed. Factors such as the valve structure are taken into account to establish appropriate countermeasures. The part of a gate valve where problems often arise when opening it is the packing area; once this packing is compressed, the non-metallic packing contains a certain amount of moisture and other substances, which cause corrosion with the metal valve stem and prevent proper operation. The treatment method involves, under the condition that the load can be controlled, loosening the packing gland (or removing some of the packing), hitting the valve stem with a hammer, and trying to rotate the handwheel by applying force; lubricants such as loosening fluids can also be used. However, this method must be carried out within the limits set by safety operating procedures. For the daily maintenance and protection of valves, such valves should be given appropriate protection against rain and corrosion. Regularly apply grease and other lubricants (that do not react chemically with the medium inside the pipe) to the valve stem, and move the valve stem periodically to keep it lubricated. For valves in critical locations, it is recommended to use valves with a higher pressure rating or special valves made of corrosion-resistant metals. . . . . . The above methods are not applicable when problems occur inside the valve; only by disassembling the valve (or disassembling it online under controlled load conditions) can insights be obtained.