Stem threads are mainly divided into trapezoidal threads and ordinary threads.The threaded fasteners on the valve directly bear the pressure of the medium and play an important role in preventing the leakage of the medium. Therefore, the selected material ensures that the valve has sufficient strength and impact toughness under the working temperature and pressure of the valve.These two types of thread damage mainly include corrosion, breakage, and thread pair over-fitting.In order to ensure the normal use of the valve stem, the thread of the valve stem must be repaired.The surface of the trapezoidal thread can be repaired with a file and sanded with emery cloth; if the thread pair is too tight, an abrasive paste can be applied to the thread for mutual grinding; and the circle can be trimmed with a small file.For the damage of the ordinary thread of the valve stem, there are several ways to repair it.
1. Inlay plugging method
Cut off the thread of the damaged part, then drill and tap the end face of the square tenon, then combine the manufactured screw plug with the valve stem, and stick it firmly with glue.
2. Thread reformation
Cut off the thread of the damaged part, drill and tap the end face of the square tenon, and then insert the spring forging ring between the screw and the handwheel.
3. Shorten the stem
If the thread is severely damaged or the square tenon is partially damaged and cannot be repaired, the thread and the square tenon can be cut off, and then processed according to 2.
4. Partial replacement
Cut off the thread that cannot be repaired, and then replace it with a new one.