What is a globe valve?

The axis of the stem of the globe valve is perpendicular to the sealing surface of the valve seat. The valve stem has a relatively short opening or closing stroke and a very reliable cutting action, making it very suitable for use as a medium for cutting, adjusting, and throttling. Once the valve disc of the globe valve is in the open position, there is no longer contact between its valve seat and the sealing surface of the valve disc, and it has a very reliable cutting action. This type of valve is very suitable for cutting off, regulating, and throttling media.Globe valve, also known as shut-off valve, is one of the most widely used types of valvesThe reason why it is widely popular is because the friction between the sealing surfaces during the opening and closing process is small, it is relatively durable, the opening height is not large, it is easy to manufacture, and easy to maintain. It is not only suitable for medium and low pressure, but also for high pressure.

Working principle of globe valve

The stem of a globe valve usually rotates and lifts, with a handwheel fixed at the top of the stem. When the handwheel is rotated clockwise, the thread of the valve stem rotates downwards, and the sealing surface of the valve disc is in close contact with the sealing surface of the valve seat, and the shut-off valve reaches the closed state; When the handwheel is rotated counterclockwise, the valve stem thread rotates upwards, the sealing surface of the valve disc disengages from the sealing surface of the valve seat, and the shut-off valve opens. Once the globe valve is in the open state, there is no longer contact between its valve seat and valve disc sealing surface, so its sealing surface has less mechanical wear. As most globe valves have valve seats and discs that are relatively easy to repair or replace, there is no need to remove the entire valve from the pipeline when replacing sealing components. This is very suitable for situations where the valve and pipeline are welded together. When the medium passes through this type of valve, the flow direction changes, so the flow resistance of the shut-off valve is higher than that of other valves.

Advantages of globe valve

a. Compared with gate valves, globe valves have a simpler structure, usually with only one sealing surface on the valve body and disc, which has a smaller sealing area, saves valuable materials, and is low-cost. Therefore, the manufacturing process is better and easier to maintain.

b. The wear and abrasion of the sealing surface are relatively light, and the sealing performance is good. When opening and closing, there is no relative sliding between the valve disc and the sealing surface of the valve body (except for the conical sealing surface), so the wear and abrasion are not serious, the sealing performance is good, and the service life is long.

c. The opening height is small, usually only 1/4 of the diameter of the valve seat channel, with a compact structure that saves installation space.

Disadvantages of globe valves

a. The structural length is relatively long.

b. The opening and closing torque is large, making it difficult to open and close. When closing, because the movement direction of the valve disc is opposite to the action direction of the medium Pressure, the force of the medium must be overcome, so the opening and closing torque is large.

c. High flow resistance. The medium channel in the valve body is relatively tortuous, with large flow resistance and power consumption. Especially in hydraulic devices, this Pressure loss is particularly obvious. Among various types of shut-off valves, the shut-off valve has the highest flow resistance.

d. The flow direction of the medium is restricted. When the medium flows through the shut-off valve, it can only flow from bottom to top or from top to bottom at the valve seat channel, so the medium can only flow in one direction and cannot change the flow direction.

e. When the valve is closed, solid particles in the fluid medium may be trapped between the sealing surfaces

f. Installation is inconvenient.

The commonly used types of globe valves are as follows:

1、 Angle stop valve: in the angle stop valve, the fluid only needs to change direction once, so that the Pressure drop through the valve is smaller than that of the conventional stop valve

2、 Once through stop valve: in once through or Y-shaped stop valves, the flow passage of the valve body is in a diagonal line with the main flow passage, so the damage degree of the flow state is smaller than that of the conventional stop valve, and the Pressure loss through the valve is correspondingly smaller.

3、 Piston type globe valve: This type of globe valve is a variation of conventional globe valves. In this valve, the valve disc and seat are usually designed based on the plunger principle. The valve disc is polished into a plunger and connected to the valve stem, and the sealing is achieved by two elastic sealing rings fitted on the plunger. Two elastic sealing rings are separated by a ring, and the sealing ring around the plunger is pressed firmly by the load applied to the valve cover by the valve cover nut. The elastic sealing ring can be replaced and made of various materials. This valve is mainly used for "opening" or "closing", but it is equipped with a specially designed plunger or special ring, which can also be used to adjust the flow rate.