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Cut-off valves key property and selects the principle

View Times  Update time 2009-02-10
The cut-off valve is refers to shutting down (valve petal) along the valve seat middle line migration valve. According to the valve petal's this kind of motion form, the valve seat passes the mouth the change is and the valve petal
The traveling schedule becomes the proportional relationship. Because this kind of valve's valve lever opening or the closure traveling schedule are relatively short, and has the very reliable cut-off function, also as a result of valve seat
Passes the mouth the change and the valve petal traveling schedule becomes the proportional relationship, very suitably to current capacity adjustment. Therefore, this type valve very suitable achievement cut-off or
Adjusts as well as reduces expenses to use.
Once cut-off valve's valve petal puts aside from the off-position, its valve seat and between the valve petal packing surface no longer has the contact, therefore its packing surface machinery attrition very
Is small, therefore its sealing property is very good. The shortcoming will be between the packing surface will possibly grip in the flowing medium pellet. But, if makes the valve petal the steel ball or the porcelain ball,
This question was also easily solved. Because the majority of cut-off valve's valve seat and the valve petal is quite easy to repair or the replacement, moreover when repair or replacement potted component
Does not need to disassemble the entire valve from the pipeline, this when the valve and the tube seam welding becomes a body's situation is suitable.
Because the medium has had the change through this kind of valve's flow direction, therefore cut-off valve's smallest resistance to flow is also higher than the majority other types the valves. However
But, is opposite according to the valve chest structure and the valve lever in the import and export channel's layout, this kind of condition is may improve. At the same time, because the cut-off valve valve petal opens in closes it
The traveling schedule is small, the packing surface can withstand opens many times shuts, therefore it is very suitable in needs the frequent switch's situation.
The cut-off valve may use in the majority of medium flow system. Has developed satisfies department each use and so on petrochemical, electric power, metallurgy, urban construction, chemical industry many kinds of
Form cut-off valve.
Cut-off valve's use is extremely ordinary, but because opening and the closure moment of force are big, the structural length to be long, usually the nominal passes after limits below 250mm,
Also has to 400mm, but selects time needs the special attention import and export direction. Generally the 150mm following cut-off valve medium flows in mostly from valve petal's underneath, but
the 200mm above cut-off valve medium flows in mostly from the valve petal's place above. This considers valve's closure moment of force result. In order to reduce opening or the closure moment of force,
In generally the 200mm above cut-off valve supposes the by-pass or outside the by-pass valve.
The cut-off valve most obvious merit is:
1st, in opens and in the closure process, because the valve petal's is smaller than in valve chest packing surface between friction force the gate valve, thus is wear-resisting.
2nd, opening is only highly generally the valve seat channel diameter 1/4, therefore is smaller than the gate valve many.
3rd, usually in valve chest and on valve petal only then a packing surface, thus makes the technology capability to be quite good, is advantageous for the service.
But, cut-off valve's shortcoming is also not allow to neglect. Its shortcoming is mainly the resistance to flow is quite all big, therefore creates the pressure loss, in the hydraulic unit, this pressure loss especially is specially obvious.
Suitable situation
Cut-off valve's application unusual widespread, many situations apply the cut-off valve. But, does not use the structural style according to the cut-off valve, is suitable the situation is also different.
1st, needle cut-off valve
Takes the precise flow control to use. The valve petal usually makes a body in the valve lever, it has one with the valve seat coordination, the precision very high needle zhuang forehead. Moreover the needle cut-off valve valve lever thread's pitch ratio common ordinary cut-off valve's valve lever thread pitch must be thin. In the usual situation, the needle cut-off valve valve seat hole's size is smaller than the line size. Therefore, it is only usually restricted, in the nominal passes after the small pipeline in is suitable, more uses in the sampling valve.
2nd, direct-current type cut-off valve
The direct-current type cut-off valve's valve lever and the channel become certain angle, its valve seat packing surface and the import and export channel also have certain angle, the valve chest may make the integral type or separate-like. The valve chest separates-like the cut-off valve to clamp with two valve chests the valve seat in, is advantageous for the service. This kind of cut-off valve causes the fluid not to change the flow direction nearly, the resistance to flow is smallest in the cut-off valve. The valve seat and the valve petal packing surface may the built-up welding hard alloy, cause the entire valve to bear the washout and the corrosion, tallies in the aluminum oxide technique of production flow pipeline control, simultaneously also suits in has coking and in the solid particle pipeline.
3rd, angle type cut-off valve
The angle type cut-off valve's biggest merit is may install the valve in circuitry's corner, like this both saved 90° the bend, and is advantageous for the operation. Therefore, this kind of valve most suits in the fertilizer plant synthetic ammonia production system neutral refrigeration system uses. Like J44H-160, J44H-320, L44H-160, L44H-320 completely are design for the synthetic ammonia production system.
4th, steel ball or porcelain ball seal cut-off valve
This valve's unique feature is the valve chest divides into the writing style and the fission type, the valve petal is continually the STL hard alloy steel ball or for the crystalless material the porcelain ball which after the milling forming, the high temperature agglutination, researches in thorough detail makes. The valve lever lower extremity trundle envelope spheroid in the valve lever ball hole, the spheroid makes the three dimensional rotation when valve lever's ball hole may produce the innumerable strip seal line, increased the packing surface service life greatly, but can also guarantee the reliable seal. This valve as a result of the spheroid seal's limit, uses in the small nominal passing generally passes through, approximately is 6~25mm. This valve is suitable for the nuclear power plant, the thermoelectric power station high temperature high pressure steam pipeline, the sample, the pollution discharge system's measuring appliance pipeline as well as the petrochemical, the chemical engineering department
In series heat resistance, pressure resistance, wearability, on anti-corrosive pipeline.
5th, high temperature high pressure power plant cut-off valve
This valve's unique feature is the valve chest and valve cover's connection uses the pressure from the tight sealed type either the collar type, the valve chest and pipeline's connection form is the butt welding connection, the valve chest material uses the chrome-molybdenum steel or the chromium molybdenum vanadium steel much, the packing surface mostly built-up welding hard alloy. Therefore, this kind of valve thermostable high pressure, the thermal resistance is good; The packing surface wearability, bears the abrasion, anti-corrosive, the sealing property is good, the life is long. Most is suitable for the thermal power industrial system, the petroleum chemical industry system and the metallurgy and so on high temperature high pressure rests, the steam, the oil quality, on the superheated steam pipeline.
6th, API cut-off valve
This kind of cut-off valve participates in ASME the B16.34 standard carrying on the design strictly; The valve chest and valve cover's connection, the packing box, valve stem nut's installment, on the seal and so on strictly carries on the design according to API600. The valve selection meets the API600 requirement completely. The structural length conforms to ASME B16.10; The flange connection size conforms to ANSI/ASME B16.5a. Valve's examination and the experiment carry on strictly according to API598. Therefore, this valve widely is suitable the petroleum chemical industry pipeline, in systems and so on electric power, metallurgy, spinning and weaving is also suitable.
7th, the oxygen pipeline uses the cut-off valve
This valve carries on the design strictly according to the oxygen pipeline's request. The stuffing box part seals strictly, the outside contamination cannot enter in absolutely the stuffing box. The valve chest both sides flange has the grounding, installs after the pipeline finished, receives, took strict precautions against the static electricity to be on fire. This valve's shell material for the austenite stainless steel or the copper material, the electric conduction good, is not easy to have the static electricity to be on fire. Seals the material for the teflon to the valve chest main body material, is the soft seal, the sealing property is good, the gas examination spillage is zero. This valve before the assembly after carbon tetrachloride degreasing processing, does not have the fat and the contamination absolutely strictly, does not send causes the static electricity to be on fire. This valve is suitable for the metallurgy system's oxygen pipeline, is also suitable on other profession's oxygen pipeline.
8th, petroleum liquid gas cut-off valve
This valve specially for petroleum liquid gas pipeline or installment design. In the structure has paid attention to the fire protection request. The padding uses the teflon reliably, the seal leaks beyond the material world absolutely. Seals the vice-material to use the teflon or the nylon to the valve chest main body material, is the soft seal, the seal is reliable. This valve is suitable for the liquified petroleum gas circuitry, takes the start-stop system, is also suitable for other temperature ≤80℃ pipeline.
9th, on thread valve lever cut-off valve
This kind of cut-off valve's valve lever not with actuating medium immediate contact. According to the shell material, seals the vice-material, the packing, the valve lever material to be different, is suitable for the different operating mode. If the valve chest, the valve cover material is the carbon steel, seals the vice-material is the alloy steel, the padding is the flexible graphite, the valve lever material is Cr13 is the stainless steel, is suitable in the water, the steam, the oil quality pipeline; If the valve chest and the valve cover material is 1Cr18Ni9 or 0Cr18Ni9, seals the vice-material for the valve chest itself material or the hard alloy, the padding is the teflon, the valve lever material is Cr17Ni2, is suitable in take the nitric acid as in base's corrosive medium pipeline or the installment; If the valve chest valve cover material is
1Cr18Ni12Mo2Ti either 0Cr18Ni12Mo2Ti, seal the vice-material for the valve chest itself material or the hard alloy, the padding are the teflon, the valve lever material are 1Cr18Ni12Mo2Ti, is suitable in take the acetic acid as in base's corrosive medium pipeline or the installment. In however this kind of cut-off valve's biggest nominal passes after is the 200mm,200 above cut-off valve must suppose in the by-pass valve or the design establishes the by-pass structure. Generally, DN≥200mm cut-off valve's import end in the valve petal's place above, namely Gao Jindi leaves, this is for prevents when the closure too takes the trouble and the valve lever excessively thick reason.
10th, under thread valve lever cut-off valve
This kind of cut-off valve Arab League valve lever thread with the actuating medium contact, the medium corrosion, causes the valve lever thread easy to rust away, to create directly directly opens shuts the hard sledding. This
Plants the structure cut-off valve its nominal to pass after is quite small, generally between 6~50mm, the majority uses in the measuring appliance valve and the sampling valve.
11th, API602 forging steel cut-off valve
This kind of cut-off valve carries on the design according to American Petroleum Association standard API602, the valve chest and the valve cover carbon steel or stainless steel forging becomes, the valve chest and the valve cover connection have
The bold fastening, the screw joint add the welding, has the thread valve lever and under division the thread valve lever, seals the vice-material is the Cr13 steel, the stainless steel acid steel is flinty to STL
The alloy, the padding for the flexible graphite or the teflon, the connection mode has the flange, the thread, to receive inserts welds with the butt welding, the pressure rating is CL150~CL1500,
The nominal passes after is 1/4~2. Widely applies in department installments and the pipeline and so in petroleum chemical industry, electric power, chemical industry, actuating medium for steam, oil quality,
Corrosive medium. The structural length according to ASME B16.10, the flange connection size according to ASME/ANSI B16.5a, welds the end size to conform to ASME B16.25, receives inserts
Welds the hole size to conform to ANSI B16.11, the thread coupling end size conforms to ANSI B1.20.1.
12th, plunger cut-off valve
This kind of plunger valve is the radial direction seal, realizes by the wrap in the polish plunger Shangdi two elastic seal packing collar. Two elastic seal packing collar isolates start with an eye ring,
And exerts in the valve cover Shangdi load through the valve chest and the valve cover connecting bolt the elastic seal packing collar presses the plunger around the jail, the guarantee seal. This valve material combination is
The shell uses the carbon steel, the plunger with the Cr13 stainless steel, the seal packing collar with the flexible graphite, may use in the water, the steam, the oil quality pipeline; If the shell uses the stainless acidproof steel,
The plunger with the stainless acidproof steel, the seal packing collar uses the teflon, is suitable in the acid, the alkalis corrosive medium. This valve merit is the seal is reliable, the life comparison is long,
Services easily; The shortcoming is opens shuts the speed to be slow. This kind of valve widely applies in the urban construction system, the city heats on the water, the steam pipeline.
Selects the principle
The cut-off valve applies one of broadest valves class, along with the ball valve and reed valve's development, the cut-off valve application's situation is substituted a part, but from cut-off valve itself
The characteristic, the ball valve, the reed valve cannot substitute, it selects the principle is:
1st, high temperature, the high-pressured medium's pipeline or installs selects the cut-off valve suitably. Like the thermoelectric power station, the nuclear power station, the petroleum chemical industry system's high temperature, on the high-pressured pipeline select
The cut-off valve is suitable.
2nd, on pipeline to resistance to flow request lax pipeline on. Namely to pressure loss consideration not big place.
3rd, the small valve may select the cut-off valve, like pin valve, measuring appliance valve, sampling valve, pressure gauge valve and so on.
4th, has the flow control or the pressure control, but to adjusts the accuracy requirement not to be high, moreover the pipeline diameter is also quite small, if the nominal passes after ≤50mm the pipeline on, selects the cut-off valve or the throttle valve suitably.
5th, in the synthetic industry production's small chemical fertilizer and the big chemical fertilizer select nominal pressure PN160 suitably nominal pressure 16MPa either PN320 the nominal pressure 32MPa high-pressured angle type cut-off valve or the high-pressured angle type throttle valve.
6th, in the aluminum oxide Bayer process production on the pipeline which escapes the silicon workshop, easily to coke, easy to select the valve chest to separate-like, the valve seat to be possible the destination, the hard alloy to seal the vice-direct-current type cut-off valve or the direct-current type throttle valve.
7th, in urban construction's water supply, the heating project, the nominal passes after the small pipeline, may select the cut-off valve, the by-pass valve or the plunger valve, if the nominal passes after is smaller than on the 150mm pipeline.
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