Working principle:

The globe valve (J) is a rising stem, and the handwheel rotates and rises with the stem. Gate valve (Z) is a hand wheel rotation, the stem does upward motion. The flow is not the same, the gate valve is required to be fully open, the globe valve is not. Gate valve has no import and export direction requirements, stop valve has a specified import and export.

Gate valves and globe valves are the two most common types of shut-off valves.

shape

Gate valves are shorter and taller than globe valves, and open stem valves in particular require higher height space. ? Gate valve sealing surface has a certain degree of self-sealing ability, its spool by medium pressure tightly contact with the sealing surface of the seat, to achieve tight leakage. Wedge gate valve spool inclination is generally 3~6 degrees, when forced to close excessive or large temperature changes the spool is easy to jam. Therefore, the structure of high temperature and high pressure wedge gate valve has taken certain measures to prevent spool stuck. When the gate valve is opened and closed, the spool and the sealing surface of the valve seat always contact and friction with each other, so the sealing surface is easy to wear, especially when the valve is close to closing, the pressure difference between the spool and the front and back is very large, and the sealing surface wear is more serious.

Compared with the globe valve, the main advantage of the gate valve is that the fluid flow resistance is small. The flow resistance coefficient of the ordinary gate valve is about 0.08~0.12, and the resistance coefficient of the ordinary globe valve is about 3.5~4.5. The opening and closing force is small, and the medium can flow in two directions. Defect is complex, highly size is larger, sealing surface Nun damage easily. The sealing surface of the globe valve must be forced to close the valve to achieve seal, under the same caliber, working pressure and the same driving device, the driving torque of the globe valve is 2.53.5 times of the gate valve. This point in the electric valve torque control mechanism adjustment, should be paid attention to.

The sealing surface of the globe valve only contacts with each other when it is completely closed, and the relative slip of the forced closing spool and sealing surface is small, so the wear of the sealing surface is small. The wear of the globe valve sealing surface is mostly due to the sundries before the spool and sealing surface, or because the closed state is not tight, resulting in high-speed erosion of the medium.

Installation mode

When the globe valve is installed, the medium can enter two ways from the bottom of the spool and from the top. The advantage of the medium entering from below the spool is that when the valve is closed, the disc is not under pressure, which can extend the service life of the disc, and can be replaced under the condition of the pressure of the pipeline in front of the valve. The disadvantage of the medium entering from the lower part of the spool is that the driving torque of the valve is about 1.051.08 times that of the upper part. The axial force of the valve stem is large, and the valve stem is easy to bend. For this reason, the medium enters from below, generally only applicable to small diameter manual globe valve, with the valve closed when the medium acting on the spool force is not greater than 350kg. Electric stop valve is generally used to enter the medium from above. The disadvantage of the medium entry from above is the opposite of the entry from below.