The opening and closing parts of the globe valve is a plug-shaped valve flap, the sealing surface is flat or conical, the valve flap along the center line of the fluid for linear movement. Stem movement form, there are lifting stem (stem lift, handwheel does not lift), there are also lifting rotating stem (handwheel and stem with rotating lift, nut on the valve body). The role of the globe valve only applies to the full open and full closed, not allowed for regulation and throttling. This is mainly determined by the characteristics of the globe valve, see below:
The most obvious advantages are:
- In the process of opening and closing, because the valve flap in the valve body sealing surface of the friction between the valve is smaller than the gate valve, and thus wear-resistant.
- The opening height is generally only 1/4 of the diameter of the seat channel, so it is much smaller than the gate valve.
- Usually only one sealing surface in the valve body and valve flap, thus manufacturing process is better, easy to maintain.
- The performance of the globe valve, mainly play the role of cutting off the pipeline medium. Compared with the gate valve, better regulating performance, small opening height, short closing time, easy to manufacture and maintain, the sealing surface is not easy to wear and tear, abrasion, better sealing performance, long service life; globe valve valve body structure design is more zigzagging, so the flow resistance is large, large energy consumption; for steam, oil and other media, should not be used for viscosity, with particles, easy to coking, easy to precipitate the media. Medium and high pressure globe valve, large diameter globe valve can be used to balance the structure of the extension of the globe valve – throttle valve, by changing the cross-section of the flow path to control the pressure and flow of the medium, in addition to the opening and closing parts of the streamlined conical, most of the other are the same as the globe valve.
Globe valve open, the opening height of the valve flap, for the nominal diameter of 25% ~ 30%, the flow has reached the maximum, that the valve has reached the fully open position. So the full open position of the globe valve should be determined by the travel of the valve flap.
Advantages of globe valve:
- simple structure, manufacturing and maintenance is relatively convenient.
- Small working stroke, short opening and closing time.
- Good sealing, small friction between the sealing surface, longer life.
Disadvantages of globe valve:
- Fluid resistance, the force required to open and close the larger.
- Not suitable for particles, viscosity, easy to coking medium.
- Poor regulation performance.
Scope of use:
- It is suitable for cutting off valve on the pipeline of fluid medium of heat-conducting oil, poisonous, flammable, strong permeability, polluting environment, radioactive, and can also be used for regulation, which is a high-quality product for creating a non-leakage factory. The valve castings are all precision casting.
- Shut-off valve is a valve where the closing member (valve flap) moves along the centerline of the valve seat. According to this form of movement of the valve flap, the change of the seat orifice is proportional to the valve flap stroke. Because the stem opening or closing stroke of this type of valve is relatively short and has a very reliable cut-off function, and because the change in the seat orifice is proportional to the travel of the valve flap, it is very suitable for regulating the flow rate. Therefore, this type of valve is very suitable for cutting off or regulating and throttling, the same pneumatic ball valve is also applicable.
The role of the globe valve under the influence of its selection principles are:
- 1, high temperature, high pressure media pipeline or device should be selected on the globe valve. Such as thermal power plants, nuclear power plants, petrochemical systems, high temperature, high pressure pipeline.
- 2, the pipeline on the flow resistance requirements are not strict pipeline. That is, the pressure loss is not a big consideration.
- 3, small valves can choose needle valves, instrumentation valves, sampling valves, manometer valves, etc..
- 4, there is flow regulation or pressure regulation, but the regulation of precision requirements are not high, and the pipeline diameter is relatively small, such as the nominal diameter ≤ 50mm pipeline, it is appropriate to use.
- 5, synthetic industrial production of small fertilizers and fertilizers should be selected nominal pressure PN160 nominal pressure 16MPa or PN320 nominal pressure 32MPa high-pressure angle shut-off valve or high-pressure angle throttle valve.
- 6, alumina Bayer method of production of desiliconization workshop, easy to coking pipeline, it is appropriate to use the valve body separate type, the valve seat can be removed, carbide sealing vice DC globe valve or DC throttle valve.
- 7, urban construction of water supply, heating project, the nominal diameter of the pipeline, can choose to cut off, balancing valve or piston valve, such as the nominal diameter of less than 150mm of the pipeline.