If the medium have went through the throttle mouth, the pressure were still lower than the medium saturated steam pressure. The air bubble will retain in throttle mouth, we will call it the flash vaporization. The flash vaporization can produce seriously destruction to the valve core, the contour characteristic which is washed out the surface has smoothly polishes, like the chart shows. Washes out destroys the most serious place generally is the speed of flow highest place, usually is located between or nearby the valve core and the valve seat. In particular in small opening, throttle gap small, under the speed of high flow environment, flushes the eclipse to destroy is also most serious. Therefore, the high pressure valve should evade a small opening work as far as possible. Even good valve, if will be in a small opening work for a long time, its life will become doubles reduces. Must avoid a small opening work, the key to the computation, the choosing, this is the design institute and the user must pay attention to doubly.

The Flash vaporization configuration of flash vaporization destroys

Steam eclipse

On the other hand, if the medium flows after the throttle mouth the medium pressure build-up to the medium saturated steam pressure， the air bubble can burst or explodes in, thus has the steam eclipse. The steam bubble bursts releases the energy, and produces the noise which is similar to the sand and crushed stone has flowed the valve. If air bubble in approaches in the valve, releases the energy can slowly rend the material, leaves behind the honeycomb-shaped eyelet. The destructive effect of the steam eclipses may extend to the neighbor downriver pipeline. Obviously, looked from the pressure recovery factor that, high restores the valve quite to be easy to have the steam to eclipse, because its throttle mouth pressure has the possibility to rise saturated to steam above the steam pressure to the medium.

The representative configuration of flash vaporization destroys

The relations between the flash vaporization and the steam eclipse, flushes:

When in small open Cv working, the speed of flow in throttle mouth is quicker, pressure is lower, content of the air bubble in the medium are more, therefore, this time the flash vaporization destroys seriously, washes out the destruction is the principal contradiction. When in wide open Cv working, the principal contradiction is the system pressure build-up to the above bubble point pressure when creates steam eclipse destruction. Therefore, user when uses the high differential pressure valve should avoid small open Cv working as far as possible, the high-pressured valve must have the better counter- steam eclipse measure, otherwise, the valve is destroyed quickly because of action of the steam eclipse, the flash vaporization.

Z口口S single seat loaded type smart counter-steam eclipse high pressure urea special-purpose control valve

Z口口S single seat loaded type smart counter-steam eclipse high pressure urea special-purpose control valve can serve the operating mode like the high pressure or the high differential pressure, has the serious steam to eclipse, to flush the eclipse under the severe operating mode condition the life short, the valve stem is easy to break, the bushing is easy to fall off and so on. It’s greatly enhanced the high differential pressure regulating valve service life, specially uses in the urea system the P4 valve compared to the ordinary high-pressured the valve life can enhance 2-3 time, and has many merits like the good vibration-proof performance, the low noise, bears washes out, resistance the corrosion, the high differential pressure, the long life, the use is reliable, services is convenience and so on.

● Main merit:
1.Uses the counter- steam eclipse measure of the multistage throttle to share the differential pressure, can improve the valve service life, if can avoid small open Cv working, the service life may amount to above for 2 years.

2.Uses the new material U3 steel which can bear the steam to eclipse, anti-flushes the eclipse, is produced in the P4 valve plug, seat. Under the same operating mode, the life also may lengthen time or once more, reduces the use cost(The U3 steel has not only all the A4 elemental composition ,but also increases borne urine element, has anti-washes out, resists corrosion ability)

3. the size is small, the weight is light, the structure is simple, disassembles and assembles, the maintenance is extremely convenient.

● Counter- steam eclipse structure analysis

First throttle-- reducing piece （①place）

Second level of throttle—single seated throttle(main throttle, ②place)

Sing seat valve structure, approximately composes 30% of the total pressure drop.

Third level of throttle –Cage throttle(③ place)

Cage structure, approximately composes 60% of the total pressure drop.

"The orifice + single seat valve + cage valve" three level of throttle structure, will separate the pressure drop which go through the valve from some smaller pressure drop, each smaller pressure drop will guarantee its pressure in the most narrow surface is bigger than the saturated steam pressure, will avoid or reduce the flash vaporization to destroy the valve. Simultaneously cage throttle which uses the eyelet spraying structure replace the way of “the guidance bushing +valve seat”, may reduce the reverse flow to destroy the plug and the throttle noise, as the way of eyelet sprays has withstood the valve throttle pressure drop majority (approximately 60%), may move the steam eclipse destructive effect by the valve seat to the eyelet, has protected the packing surface, enhanced the valve service life, may reach the ordinary high differential pressure valve 2 ~ 3 times.

● Counter- steam eclipse measure

We use the hard alloy at the past is not very good, now, we adopt U3 steel which have better performance in degree of hardness and toughness, can bear the steam eclipse and washes our.

In 70’s, we often use the orifice craft technology to reduce the pressure drop, now, we can set the resistance in the valve to achieve better fall pressure effect.

Prevents small open Cv working, reduces the speed of fluid

Chooses the fluid way, change small valve like straight travel angle valve to reduce the pellet impact as soon as possible.

Flexible flow will create partial flushes the eclipse seriously, we should use the mothed of dispersing flexible flow to overcome.

Adopts multi-stage throttle structure, will enhance the valve service life by reduce the pressure drop.

Increases the stem diameter, enhances the stem rigidity, prevents break.

When used in heavy-caliber, big differential pressure, we should match the pneumatic cylinder actuator.