Matters Needing Attention of Forged Steel Gate Valves
Jul 28, 2017
The disc of the forged steel gate valve is the gate, whose direction of movement is perpendicular to the flowing direction of the fluid. The forged steel gate valve can only be fully open or fully closed, and it can not be used as control valves and throttle valves. There are two sealing surfaces of forged steel gate valves' gates, and the most common pattern is that the two sealing surfaces of gate valves become wedge-shaped or wedge-angled changing with the parameter of valves.
The driving modes of forged steel gate valves are: the manual mode, the pneumatic mode, the electric mode and the pneumatic hydraulic mode.
The gate valves can be classified as cast iron gate valves, ductile iron gate valves, stainless steel gate valves, forged steel gate valves, etc. according to different materials.
As a sort of gate valves, all gate valves that are made of forging materials are collectively known as forged steel gate valves. The forging materials can be classified as A105, F11, F5, 304, 304L, 316, 316L, etc.
The forged steel gate valves that are often mentioned in China usually refer to these with small diameters. The forged steel gate valves with diameters exceeding DN50 all need to be customized, and there is little demand for them in China.
Diameter Scopes: DN10~DN50
Chinese Standard: PN16 to PN320
American Standard: Class 150 to Class 500
The grease capacity
When using the grease gun to oil the forged steel gate valve, the operating personnel can go ahead with the greasing process after determining the mode of connecting the valve and the grease. There exist two circumstances of forged steel gate valves. On the one hand, it would accelerate the wear of sealing surfaces due to the lack of lubricant if there is little grease. On the other hand, it would result in waste if there is excessive grease. This is because people do not accurately do calculation for the sealing capacity of different valves according to different types and categories. People can calculate the sealing capacity of valves based on their sizes and categories and then add suitable amount of grease.
During the greasing process, there are regular peak and trough changes of the greasing pressure. When the pressure is too low, the safety valve would lose their effects; when the pressure is too high, the valve of grease injection opening would block; the sealing grease would harden, or the sealing ring would be tightly connected with the ball or plate of the valve. Usually, when the greasing pressure is too low, the injected grease often flows into the bottom of the valve cavity, and this case generally happens on the small-sized gate valves. When the greasing pressure is too high, firstly the grease opening of insulated gate valves should be checked, and if the valve opening of the float valve blocks, the spring, the seal tape and the full-open wrench need to be replaced after accurate judgments. On the other hand, the cleaning fluid should be used to repeatedly soften the invalid sealing grease and the new grease needs to be injected as the replacement if the original grease hardens. Besides, the sealing modes and sealing materials will also affect the pressure of grease, and different sealing modes have different grease pressure. Generally speaking, the pressure of the hard sealed grease injection tends to be higher than that of the soft sealed grease injection.
The open and closed states
The gate valves are usually in the open state when being maintained. However, people sometimes also keep valves closed when valves are being maintained under exceptional circumstances. It can't be said that all the other valves should be opened when being maintained. The forged steel gate valves must be in the closed state when being maintained, which can make sure that the grease along with the sealing ring can fill the whole sealing groove. If forged steel gate valves are opened when being maintained, the sealing grease will directly fall into the flow channel or the valve cavity and thus result in waste. When the valves are being greased, the effect of greasing tends to be neglected. The pressure, grease capacity as well as open and closed state should be normal during the greasing process. However, in order to ensure the effect of greasing, sometimes people need to open or close the valves to examine the lubricating effect and confirm that whether the ball of the valve or the surface of the gate is lubricated evenly.
NO. 879, Xiahe Road, Xiamen, Fujian, China
086 592 5819200