Wear resistant working condition

Wear resistant working condition

The valves can undergo wear for various and numerous causes, but the main reason that causes the deterioration of the valves is the wear of the solid particles of the conveyed medium. However, it is possible to take specific measures to improve the wear resistance of the valves. Among these we include:

Improve material hardness

Research on the resistance of materials to abrasive wear shows that abrasive wear depends on the relationship between the hardness of the metal Hm and the abrasive hardness Ha. When Hm / Ha> 0.8, the amount of wear on the metal decreases rapidly and when Hm / Ha = 1.25-1.3, the amount of wear is already very low. It can be noted that if you want to reduce abrasive wear it is necessary that the hardness Hm of the metal material is 1.25-1.3 times greater than the hardness Ha of the abrasive, that is Hm = (1.25-1.3) Has.

This data can be used to evaluate the wear rate! The amount of wear is divided into three regions corresponding to the relative hardness. However, although the sealing surfaces of the valve disc and valve seat used in our country’s alumina plants are all made of

cemented carbide, the hardness value is lower than that of the abrasive. This means that the ratio of the valve disc hardness to the valve seat to the abrasive hardness is less than 0.8, such a high wear value will cause short service life of the valve.

Surface treatment

Using various surface treatment processes, the surface characteristics of the valve disc and valve seat can be changed. This method improves the abrasive wear and also improves the surface finish. It is important to remember that in addition to abrasive wear, the disc and seat are also subject to erosive wear. In fact, when the liquid conveyed is in contact with the disc and with the valve seat, the local pressure is lower than the evaporation pressure, so bubbles will form. As these bubbles flow through the high pressure area, the pressure rises until they burst, causing great damage at such a high temperature in moments. Due to the repeated formation and bursting of bubbles, the surface of the disc and the valve seat will be increasingly worn, presenting pits and voids typical of cavitation wear.Small droplets pour onto the surface of the valve disc and valve seat at very high speed (1000 m / s), causing high stress on the surface. Under these conditions, even a little stress will cause pitting corrosion, also called pitting. The way to prevent these types of wear is to increase the hardness of the material! After years of valve technology development, the wear resistance of Xinhui valve has been greatly improved. Today our valves are able to adapt to complex and severe working conditions, remaining intact and performing.