Sometimes the sealing surface is bitten, the stem bite of the stem is scratched, and the threaded part of the stem is bitten.

To explain the causes of these failures, we must first understand the causes of scratches:

1. Bonding wear produces abrasive particles. The abrasive particles have a hardness higher than that of the two base metals and are pressed into the soft surface to scratch the hard surface. At the same time, the hard abrasive particles are also moved by the hard surface peaks of the soft surface. Then plow the soft surface. After the friction surface separates, the abrasive particle may discharge, but it may still be on a soft surface. When rubbed again, it will scratch the hard surface and plow deeper and deeper trenches on the softer surface until the soft surface in front of the hard particles cannot resist the moving force of the hard particles. It is cut to form a strip-shaped groove on a soft surface and a scratched surface on a hard surface.

2. If the load is harsh and the contact is small, the contact area is greatly increased, and the generated wear debris is also increased. If it cannot be eliminated in time, nodules are formed on the surface, the shear area of the joint increases, and the wear debris is larger. The result is a frictional tumor. The process from small nodules to friction tumor formation increases gradually in the chain. When the original moving force cannot cut the friction tumor and the force cannot continue to increase, the friction pair is bitten and cannot continue to slide. It can be seen that the frictional tumor that causes occlusion must contain one or more hard or abrasive particles under shear.

3. Therefore, the scratch is caused by the presence of hard particles or the wear of abrasive particles, so the wear is to some extent a form of wear. Secondly, the valve stem can rub against the packing sleeve and packing pad. If the medium contains boron, it will crystallize into hard particles after discharge.

Pull the surface of the stem and do not lubricate the parts to which lubricant should be added.

Measures to prevent this failure are: Scratches are caused by hard particles entering or abrasive wear. Therefore, the grinding debris should be reduced as much as possible to become powdery particles, and the friction surface should be removed in time and sufficiently. The better the finishing, the better the fit, the joint increases, the actual contact area of the joint decreases, the shear force decreases, and the shear wear decreases. Therefore, it is necessary to increase the friction area or improve the smoothness under the condition of constant load, and lubricate as much as possible to further reduce the friction and promote the elimination of abrasive particles, and at the same time, it should be added on a wider friction surface. The flutes are opened to discharge the abrasive particles into the flutes and drain the friction surfaces with lubricating oil.

In order to prevent the sealing surface from being scratched, the sealing surface must be operated in a self-abrasive state, thereby reducing wear and further refining the surface so that the life of the sealing surface can be maintained and extended as described above. Specific measures are:

(1) valve cavity cleanliness strict;

(2) properly improve the sealing surface finish;

(3) Increase the contact surface;

(4) Improvement of fitness;

(5) No hard particles enter the friction surface;

(6) the abrasive particles quickly and completely eliminated;

(7) The two sides shall have hardness difference;

(8) Lubricate, reduce friction and avoid direct metal contact;

(9) less than pressure;

(10) Open a chip bag or chip breaker on a soft surface;

(11) Materials with large plastic flow pressure s y;

(12) Materials that are not prone to cold work hardening.

Secondly, the stem is wiped with other parts. The third is to install the packaging correctly or press the packaging correctly to prevent the leakage of the medium. Then, the parts that should be lubricated are added with the corresponding lubricant.