Metal-sealed globe valve
1. Straight through globe valve
The “straight through” in the straight-through globe valve is because its connecting end is on an axis, but its fluid channel is not really “straight through”, but rather tortuous. Flow must turn 90° to pass through the seat and then turn back 90° to return to its original direction. In cast valves, channel shape and area vary depending on valve size and pressure rating.
Z channel structure of the cut-off valve, or free forging die forging body body will usually import and export port and the center line of the pipeline into a certain Angle, namely the form Z flow channel, and often processed into reducing, however narrow aperture and tortuous flow will greatly increase the fluid pressure loss, in addition it should be noted that turning the acute Angle in the working condition of fluid cavitation phenomenon.
2. Angle globe valve
Trace back to the development history of the globe valve, the initial development is Angle globe valve, and then gradually developed into straight-through globe valve. Although straight-through globe valves are more commonly used today, Angle globe valves still have some unique advantages.
Angle globe valves allow flow to change 90 directions and always enter from the bottom of the seat. The runner is more open and less tortuous than the straight-through, so there is less pressure loss. Angle globe valves are not easily eroded by solid particles. Disc can be designed in claw or skirt shape for better regulation. Due to the change of flow direction, the valve body will be affected by the reaction force of the fluid. These forces are normally small but may increase due to valve size and fluid density.
Small copper alloy threaded Angle globe valves are widely used in clean water conditions. Most industrial Angle globe valves are bolted bonnet type, made of cast steel, bronze, stainless steel, and duplex steel materials.
Common dimensions and pressure classes of Angle globe valves are usually DN50~250(NPS2~10), Class 150~800. Beyond this range, a balanced disc is usually used to reduce axial fluid thrust on the stem.
3, straight flow stop valve
Straight globe valve is also known as a Y-shaped globe valve or oblique globe valve, it can be a straight-through and Angle valve in the middle of the state. In order to change the straight-through tortuous fluid channel, the valve seat hole and valve body design into a certain Angle, so that the flow channel becomes more straight with the axis, in order to reduce the pressure loss, so it is called “straight flow”. This structure is popular in most applications and is widely used in steam systems. Solid transport capacity has been greatly improved, but careful testing is needed in use. Straight flow globe valves also have only one flow direction. The runner has full diameter and reduced diameter. Not suitable for pig pigging without removing the bonnet.
Disc is usually flat, claw – guided or tapered to meet the requirements of different operating conditions. The tapered disc profile can be designed with multiple tapers to produce primary and secondary throttling. Flat disc and claw guide disc valves may be fitted with a wipe to clean the seat prior to sealing, or a rubber seal may be fitted to the seat to improve valve sealing.
Straight flow globe valves are usually cast and high pressure valves forged. According to different working conditions, special materials such as double-phase stainless steel can be selected for manufacturing.
4. Three-way globe valve
Three-way globe valves are commonly used as directional valves in high pressure systems. For example, the high temperature and high pressure water supply valves of power station boilers. Commuting is usually used when starting, shutting down, or failing.
Another more common working condition as a reversing valve is the pressure relief system. The two relief valves are mounted on a single three-way globe valve, allowing the other valve to operate normally when one of them requires isolation or service. Due to the internal structure, the three-way globe valve has high flow resistance. The change of the direction of the fluid will produce a large reaction force on the large diameter three-way globe valve.
The body of tee – way globe valves is usually cast steel or alloy steel. Valves used in power plants are butt-welded to overcome leakage problems caused by flanged connections.
Post time: Mar-24-2021