Classification of the globe valves-(1)
According to the channel direction, the globe valve is devided into 4 types:
1) Straight-through globe valve.
2) Direct flow stop valve: In direct flow or Y-shaped stop valve, the flow passage of the valve body is in a diagonal line with the main flow passage, so that the damage degree of the flow state is less than that of the conventional stop valve, so the pressure loss through the valve is also corresponding Is too small.
3) Angle type stop valve: In the angle type stop valve, the fluid only needs to change its direction once, so that the pressure drop through this valve is smaller than that of the conventional structure.
4) Plunger type globe valve: This type of globe valve is a variation of the conventional globe valve. In this valve, the disc and valve seat are usually designed based on the plunger principle. The valve clack is polished so that the plunger is connected to the valve stem, and the sealing is achieved by two elastic sealing rings sleeved on the plunger. The two elastic sealing rings are separated by a collar, and the sealing ring around the plunger is pressed firmly by the load exerted on the bonnet by the bonnet nut. The elastic sealing ring can be replaced and can be made of various materials. The valve is mainly used for “open” or “close”, but it is equipped with a special form of plunger or a special collar, which can also be used to adjust the flow .
The position of the thread on the valve stem:
1) Upper threaded stem stop valve: The thread of the stem of the stop valve is on the outside of the valve body. The advantage is that the valve stem is not corroded by the medium and is convenient for lubrication. This structure is more common.
2) Bottom thread stem stop valve: The thread of the stem of the stop valve is in the valve body. The stem thread of this structure is in direct contact with the medium, which is susceptible to corrosion and cannot be lubricated. This structure is used in places with small diameters and low temperatures.
There are many domestic manufacturers of globe valves, and most of the connection sizes are not uniform. It is mainly divided into the following categories: General category based on JB/T2203-1999 “Structural Length of Stop Valves”. At present, most domestic shut-off valve manufacturers design and produce according to this standard. However, this standard is not perfect, and the specifications are not complete. The maximum nominal diameter of a single gate valve is DN1200, and the maximum nominal diameter of a double gate valve is DN1500. According to the specifications of the shut-off valve produced by the manufacturer and the information available, the smallest nominal diameter of the angle-type shut-off valve is DN15, and the nominal diameter of the Z-type straight-through shut-off valve reaches DN2000. After research, the connection size of each manufacturer is not uniform. In order to have a unified standard, users can interchange the same specifications when selecting and installing, it is recommended that China General Machinery Research Institute revise JB/T2203-1999 “Structural Length of Stop Valves”. It is recommended that the design institute and users choose according to the standard, and the stop valve manufacturer should design and manufacture according to the standard.