Overview
The thermal adhesion of the gate valve refers to the phenomenon that the valve is closed in a hot state, and cannot be opened after cooling.
Two main reasons
When the valve is closed, the valve stem extends from the external low-temperature area to the high-temperature area inside the valve body. With the gradual heating of the valve stem, a small amount of deformation will occur in both the axial and radial directions, and the axial deformation will generate a force F1, which further increases the closing force of the valve disc. (Figure 1)
When the valve body is in the high-temperature area, the valve stem, valve disc and valve seat have different degrees of thermal expansion. The valve disc deformation produces force F3, and the valve seat force F2. The closing force at this time is greater than that when the valve is debugged at room temperatures in the factory. When the valve body is cooled, the different degrees of contraction of the valve stem, valve disc and valve seat will further increase the closing force, so that the valve plate will be stuck in the closed position. (Figure 1)
Figure 1
Thermal adhesion of wedge gate valves
For the wedge gate valve, whether it is a rigid or elastic wedge, because the dimensions of the wedge and the valve seat are different, the thermal expansion caused by the temperature change is different, so that the wedge is stuck, which may cause the wedge to fail to move. (Figure 1)
The severity of the thermal adhesion effect of the wedge gate valve depends on the change in thermal expansion under the operating conditions of the valve. Thermal adhesion is very common to be seen at high temperatures.
Thermal adhesion of parallel wedge gate valves
Thermal adhesion doesn't need to be considered for the parallel wedge gate valve due to the different sealing principles of valves, and it has a significant feature of being safe when operating at high temperatures. (Figure 2)
The seal of the parallel plate gate valve is a position seal. After the valve stem extends to the valve body, the expansion force F5 will only make the valve plate slightly downward, and the closing force between the valve plate and the valve seat does not change; the sealing specific pressure is only related to the medium pressure, and the temperature effect is very small. (Figure 2)
Figure 2
When thermal contraction occurs between the valve body cooling seals, the springs between the valve plates are slightly compressed, and the sealing force changes very little. Therefore, the parallel wedge gate valve does not experience thermal adhesion.
The thermal adhesion of the gate valve refers to the phenomenon that the valve is closed in a hot state, and cannot be opened after cooling.
Two main reasons
When the valve is closed, the valve stem extends from the external low-temperature area to the high-temperature area inside the valve body. With the gradual heating of the valve stem, a small amount of deformation will occur in both the axial and radial directions, and the axial deformation will generate a force F1, which further increases the closing force of the valve disc. (Figure 1)
When the valve body is in the high-temperature area, the valve stem, valve disc and valve seat have different degrees of thermal expansion. The valve disc deformation produces force F3, and the valve seat force F2. The closing force at this time is greater than that when the valve is debugged at room temperatures in the factory. When the valve body is cooled, the different degrees of contraction of the valve stem, valve disc and valve seat will further increase the closing force, so that the valve plate will be stuck in the closed position. (Figure 1)
Figure 1
Thermal adhesion of wedge gate valves
For the wedge gate valve, whether it is a rigid or elastic wedge, because the dimensions of the wedge and the valve seat are different, the thermal expansion caused by the temperature change is different, so that the wedge is stuck, which may cause the wedge to fail to move. (Figure 1)
The severity of the thermal adhesion effect of the wedge gate valve depends on the change in thermal expansion under the operating conditions of the valve. Thermal adhesion is very common to be seen at high temperatures.
Thermal adhesion of parallel wedge gate valves
Thermal adhesion doesn't need to be considered for the parallel wedge gate valve due to the different sealing principles of valves, and it has a significant feature of being safe when operating at high temperatures. (Figure 2)
The seal of the parallel plate gate valve is a position seal. After the valve stem extends to the valve body, the expansion force F5 will only make the valve plate slightly downward, and the closing force between the valve plate and the valve seat does not change; the sealing specific pressure is only related to the medium pressure, and the temperature effect is very small. (Figure 2)
Figure 2
When thermal contraction occurs between the valve body cooling seals, the springs between the valve plates are slightly compressed, and the sealing force changes very little. Therefore, the parallel wedge gate valve does not experience thermal adhesion.
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