Globe Control Valve

Cage Type single-Seat Globe Control Valve

Cage Type single-seat Globe Control Valve adopts the cage guided structure and pressure balanced plug. It is suitable for applications with relatively high differential pressure. The balanced sealing replaces the upper seat to change the traditional cage double-seat valve structure into the cage single-seat structure. This improvement has greatly enhanced the shutoff class of the cage valve. The plug makes use of the pressure balanced structure, the opening and closing force is low and the medium under service conditions with high differential pressure can be controlled through relatively low actuator thrust. it is widely used for liquid control on pipelines of middle and low temperature and middle and low pressure that require good dynamic stability. With such features as good sealing performance, high allowable differential pressure, cage guiding, large guiding area, good stability and compact structure, it car realize fast replacement to trims on the line with high maintenance efficiency, saving manpower and time. The balance plug structure makes sure that the actuator thrust required is the lowest.

Cage Type Double-seat Globe Control Valve

HCB Pneumatic Cage Type Double-seat Globe Control valve adopts the cage guided structure and pressure balanced plug. Different from Cage Type single-seat Type, this kind of control valve adopts the cage type double seat structure and is mainly used in applications that do not have high requirements for shut off. As it adopts the double-seat structure, and the two sealing faces are metal seals, the temperature range is wider. The plug makes use of the pressure balanced structure the opening and closing force is low and the media under service conditions with high differential pressure can be controlled through relatively low actuator thrust. lts widely used for fluid control on pipelines of middle and low temperature and that require good dynamic stability, With such features as good sealing performance, high allowable differential pressure, cage guiding, large guiding area, good stability and compact structure, it can realize fast replacement of trims on the line with high maintenance efficiency, saving manpower and time. The balance plug structure makes sure that the actuator thrust required is the lowest.

Multi-hole Low Noise Control Valve

Pneumatic Multi hole Low Noise Control Valve adopts the sleeve guided structure and pressure balanced plug.it is a high performance control valve with good dynamic stability that is suitable for severe service conditions. As the differential is relatively high and the flow velocity of medium is high, the trims will be severely eroded and damaged and high noise will be produced. Therefore, we change the standard window type sleeve in to the multichoke sleeve. for liquids the flow direction is generally high-in and low-out, and multi hole throttling makes the medium carry out collision inside the sleeve, so as to consume internal energy and reduce flow velocity. For gas and media, the flow direction is generally low-in and high-out, so that the ga medium achieves volume expansion at the back of the seat after throttling by the multi hole sleeve and the pressure of medium is reduced to lower the flow velocity. The parts of this type control valve are interchangeable with those of Cage Type single seat Control Valve except that the sleeve is changed into the Mult-hole type
Multi-Stage Pressure drop control valve

Multi-stage Pressure drop control valve adopts the sleeve guided structure and pressure balanced plug. it is mainly used in service conditions with high differential pressure and applications that produce flash evaporation and cavitation. According to different parameters, it is designed with different pressure drop cages that form a Multi-stage pressure drop trim. The cages designed according to different service conditions ensure the occurrence of fast evaporation and cavitation in the value is eliminated. Throttling is carried out from the time when the medium contact the first cage, and the high differential pressure at the inlet is gradually reduced after several times of throttling. Thus it is effectively ensured that the pressure is always above the saturated vapor pressure when the medium flow in the valve, and the occurrence of flash evaporation and cavitation is eliminated, so that the service life of the control view prolonged under severe service conditions

Cavitation cause and solution

Cause of Caviation
When the fluid pressure is reduced to the saturated vapor pressure or lower, flash evaporation or bubbles will occur.in most control valves figure 5), the inlet pressure is p1, velocity is V1. When the fluid passes through the plug necking area, the velocity is increased to Vvc According to the principle of conservation of energy, the fluid pressure suddenly drops to Pvc. When Pvc is equal to or less than the liquid saturated vapor pressure Pv, the liquid wilbe gasified and bubbles will be produced, so that flash evaporation occurs. After the fluid passes through the plug, the pressure starts to be restored and the kinetic energy is transferred into potential energy again When the pressure is restored to the downstream pressure, which is expressed as p2 and the velocity is V2. When the restored pressure exceeds the saturated vapor pressure Pv, the bubbles formed will be broken and cavitation wil occur. This kind of energy release will increase the partial stress to be above 200000psl ( 1400MPa) and the stress will rapidly destroy the solid plug.

Solution to Cavitation

The labyrinth control valve can effectively eliminate the damage caused by failure of control of fluid velocity. First, the fluids are scattered into many small flow channels. Thus, even when the bubbles are formed, their volume is very small and the energy isnot sufficient to produce stress that can damage materials, secondly, the flow velocity is maintained at the lowest level. Thus, the partial pressure will not be reduced to be lower than the fluid vaporizing pressure. Therefore, cavitation will not occur. The damage caused by cavitation is a typical signal that indicates failure of control of flow velocity. As is mentioned above, the adoption of materials of high hardness, insulating sleeve or downward orifice will only eliminate a small amount of faults in the valve caused by cavitation. The high low velocity will cause cavitation and damage the plug, and the solution to cavitation is to adopt the labyrinth cage as shown in figure?

• Relative KV values of the globe control valve and the Travel (EQ% / Linear)