Gas supply valve enterprise danyang flywheel for urban gas equipping system valve of shallow of you choice
1 natural gas requirements of the valve
1.1 underground pipe valve requirements
Underground pipe network valves should be able to bear the high pressure of natural gas pipeline network, under a variety of external forces to ensure that no deformation and sealing. When the choice should pay attention to the following:
1) as far as possible reduce the height of the valve (i.e., the centerline of the valve flow section to height) on the top of the valve, reduce the pipeline buried depth.
(2) the valve at the top of the indicator should be equipped with fully enclosed the opening and closing, is advantageous for the operator to determine the valve state, to ensure safe operation.
(3) full size design are adopted to decrease the resistance, valve detector facilitate sweeper through a pipe or pipes.
(4) reliable sealing. Soft seal valve in 1. 1 times the rated pressure are not allowed to have any internal leakage; Hard seal valve in 1. 1 times the rated pressure, internal leakage quantity should be less than the specified value; External leakage is absolutely not allowed.
(5) underground pipe gas valve casing corrosion, Suggestions according to the pipeline natural gas composition and pressure of the shell with different material.
6 valve parts design using less maintenance or free maintenance structure, as far as possible reducing maintenance workload.
All landowners mostly artificial valve opening and closing of the underground pipe network, require the valve opening and closing torque is small, the entire circle number less, can cut off the gas source as soon as possible after the accident.
Today the complexity of the urban underground pipe network underground unfavorable setting valve well, therefore recommend buried type valve.
1.2 the valve shell material selection
According to the gas transmission pipe network pressure, selects the appropriate valve shell material. Meet the pipeline safe operation and to reduce costs, choose to pay attention to the following:
(1) on the medium voltage class B and gas transmission pipeline network, under the recommended gray cast iron valve, its biggest advantage is corrosion resistant performance is good, price cheap, suitable for the underground pipe network.
(2) high voltage class B on time and under the network, the proposal chooses nodular cast iron or cast steel valves, recommended to choose the former. Mechanical properties of nodular cast iron and cast steel, and its corrosion properties and casting process are better than the cast steel, the price is lower than cast steel (typically cast steel prices by about 70%). As a result, the pressure range should be as far as possible choose ductile iron valves, but pay attention to monitoring the quality of ductile iron material.
(3) to hv A grade and above of gas transmission pipeline, suggested that choose cast steel valves.
(4) in recent years, the gas around the company started to use PE pipe, PE pipe is generally used in 0. 4 MPa pressure of gas transmission pipeline level and below.
PE ball valve can be directly buried, sealed performance is good, but the price is higher, especially ball valve DN 100 mm or more. PE ball valve is currently in use phase, the use effect reflect are different, still need to constantly sum up experience.
Two commonly used gas valve
2.1 the classification of the gas valve
1) RZ series parallel double disc gate valves
RZ series parallel double disc gate valves can be buried, maximum displacement can reach 1, 600 mm in diameter, has the following advantages: a. a stem cases, make the valve stem is not affected by corrosion. B. valve has a drain hole at the bottom, can clean the dirt at the bottom of the valve chamber. C. full size design, flow resistance is small, can pass the pig. D. adopt the cage frame type reinforcing rib design, reduce the weight of the valve, enhance strength and stiffness of the shell. E. shell use grey cast iron manufacturing, the price is cheap. F. valve open/close indicator with a totally enclosed, clear the operator valve status. RZ series gate since launch, a large number of applications in gas medium voltage class B line around the gas company, access to wide acclaim users.
(2) RQZ series parallel double disc gate valves
Parallel double ram RQZ nodular cast iron gate, retained the RZ series gate valve characteristics, on the chosen material enhances the tensile properties of valve, pressure levels increased to high voltage class B. Suitable for low pressure, the velocity slower urban underground pipe network, can be directly buried. Its shortcomings mainly valve sealing surface and gate seal face with gas contact, when fully open easily by high-speed gas flushing with dust and damage.
(3) butterfly valve
Compared with the butterfly valve and the valve, diameter is larger, price is low. Began in the early 1980 s, the gas company commonly used butterfly valve, the use of over 10 a, think the effect is not good, basically has the following reasons: a. butterfly valve is not easy to locked. B. central disc in the valve cavity, the flow resistance is big, not through the pig. C. because the part is rubber or ptfe seal, under the gas flushing is easy to damage or loss, short service life. In addition to the special position, should not be used on gas pipeline butterfly valve, some have used butterfly valve of the gas company is replacing other types of valves. Due to the small size of butterfly valve structure, also butterfly valve can be used for gas pressure regulating box, can decrease the size of the space. Should choose high quality butterfly valve, but it is best to metal seal eccentric butterfly valve.
(4) flat gate valve
Flat gate valve is started to use in recent years, low prices, full size when the flow resistance is small, on both sides of the seal by ptfe or rubber o-rings pressure formed on the gate. The valve in fully open or fitted midplane angry, not easy to repair immediately if the valve is locked. Some manufacturers make reducing, such as the DN of flat gate valve diameter is 150 mm, 200 mm, the user should pay special attention to. This kind of flat gate valve is suitable for the low pressure stage system, smaller pipe nominal diameter.
5. TRZ resilient seal gate valve series
TRZ resilient seal gate valve series is a kind of special gas mandatory seal valve, can be directly buried. On both sides of the disc sealing structure of elastic floating type, sealing surface in the process of full open, close and open/close always close together, and is suitable for the high pressure stage of pipeline. Valves in the fully open and close the valve cavity can be achieved without gas. Tossing the residual gas in the valve cavity, after checking there is no pressure in the valve cavity, can the valve downstream pipeline construction, shorten the construction before the shutdown. TRZ series connection form of the resilient seal gate valve with flange and welding type two kinds. Directly welded to the valve and pipeline welding. Its full open, full size, small flow resistance, sealing surface contact with the medium. TRZ resilient seal gate valve series disadvantage is that the height is larger at the bottom of the structure, construction of buried depth is deeper, but generally does not affect the pipeline laying.
Whole sealing elastic sealing gas gate remaining advantages of TRZ resilient seal gate valve series, increased to prevent a foreign body fall into the valve cavity internal structure, the application effect is good.
6. RQ series ball valve
Ball valve, because of the small flow resistance small, height of structure as well as good sealing performance and widely used. There are kinds of ball valves, with a diameter of ball valves due to the material, process or different structures and large difference in price.
General points two kinds of ball valve. Is a floating ball valve, the ball in the valve cavity can float, rely on each end of the seal seat clamp sphere and stable. The ball valve can only be used for nominal diameter smaller (150 mm) and stress level is low (below 0. 8 MPa) pipe, or open-close torque will be very big, use not convenient. Another kind is the fixed ball ball valve, suitable for large nominal diameter (200 mm) and stress level is high. The fixed ball ball valve when the valve is seated, the operating torque is small, convenient for operators to use.
RQ gas ball valve has the following advantages: a. fire resistance. When there is a fire and burned seal seat after ptfe material, under the action of spring, added metal seal seat sealing space continue to compress valve ball, forming metal to metal seal structure, effectively prevent the spread of the gas, to prevent the disaster. B. anti-static. In spheroid and the valve stem, valve stem and body set up between the conductive body, the valve in the opening and closing process of static electricity by setting the static channel to import the underground pipeline, to avoid the accumulation of static electricity caused lighter detonation gas, to ensure safety. C. limit lock. The rotation mechanism, the ball valve is easy to cause 360 �� rotation, limit mechanism must be designed, should also be locked when necessary, to prevent the operator wrong operation. D. stem strike. Stem with bottoms, set the inverted sealing structure with sealing gasket. Pour sealing force of seal with the valve chamber increases with the increase of gas pressure and to ensure that the valve stem seal. Stem seal in addition to using inverted sealing structure, and the use of special type O sealing ring, can make the similar small ball valve, ball valve opening and closing torque more convenient operation.
Several kinds of gas valve is 1.
1 compared several kinds of gas valve
2.2 all welded ball valve
All welded ball valves at both ends like the pipe size of the short tube, welding on the pipe directly, its advantage is to reduce the weight of the ball valve, and reduce the external leakage. But all welded ball valve technology is complex, high cost, it is recommended to use the pressure on the high level of pipeline, the following points should be paid attention to.
(1) corrosion resistance
All welded ball valve shell forging steel should be adopted. Natural gas containing hydrogen sulfide, react with iron to form iron sulfide, therefore casing corrosion is the key.
Seal directly affect the quality of the ball valve, the author suggested that users choose seat with double piston effect. The principle of double piston effect seat is equipped with 2 set of valve seat seal, if the upstream seat is damaged, gas medium into the lumen, by means of gas medium can still make the downstream pressure seal sealing effect. Seal such as can be made into hard and soft seal combination is more ideal, namely ptfe sealing, stainless steel metal elastic ring as hard seal. Such a combination of hard and soft sealing, not only enhance the sealing, it has fireproof function. After sealing the fire burned, hard seal can still sealed. Still have a kind of full welded ball valve has a rotating seat of the special structure, its advantage is the valve closing valve seat every time 15 �� rotation, will wear evenly distributed between the ball and the seat on the seat, the seat life theory raised 12 times. Seat rotate to sealing grease, cleaning fluid or lubricant evenly daub on the sealing surface, this is other ball valve cannot be achieved.
All welded ball valve nominal diameter greater than 150 mm, should be are structure of trunnion mounted ball. In order to reduce dielectric sphere and bending stress caused by the valve stem, the stem and ball got behind on the longitudinal center line, and increase the stem and ball joint stiffness, increased the strength of resistance to medium pressure valve. To reduce the number of ball valve opening and closing torque and stem circumference of a circle add bearing or at a reduced friction shims.
(4) sealing grease
Of DN 400 mm above all welded ball valve, because of the large compression is all welded, difficult maintenance, should set up emergency charging device for sealing grease.
2.3 special use of the valve
(1) voltage regulator with an emergency shut-off valve
Voltage regulator with an emergency shut-off valve (also called safety shut-off valve) is an important safety device in gas pipeline system, it is in the valve upper or side to install the emergency trip mechanism, or together as a whole, and voltage regulator for ontology can also be used to filter the tent together as a whole, its role is in voltage regulator malfunctions, overpressure or emergency shut down after the gas source pressure loss, ensure safety. Voltage regulator for the consequences of failure, need to be careful. Is an organic whole repeatedly with the filter, the structure is compact, can be in setting the overpressure and the loss of pressure quickly cut off voltage regulator source, to ensure user safety. Cutting the safety and gas filter feature set in one, saved a space already can efferent signals after the valve closed again, through on-line automatic monitoring device, may control the position of the pressure regulator valve timely notification to relevant departments, to facilitate rapid repair.
(2) gas emergency shut-off valve
Gas such as gas boiler, gas air conditioning equipment in the case of gas leakage or other accident, gas emergency shut-off valve, quick to cut off the gas source, preventing further damage, but there was no gas emergency shut-off valve in the domestic popularity. Gas emergency shut-off valve and automatic monitoring equipment generally online, to execute commands shut valve, gas emergency shut-off valve is generally electric control valve, mainly adopts the electromagnetic valve and the electric valve. Imported electromagnetic valve is used in the most of solenoid valve, the reaction speed, the flow resistance is big, the pressure loss is big, and small caliber. Large diameter electromagnetic valve manufacturing more difficult, normally only done below DN 150 mm, the price is more expensive. In addition, the electromagnetic valve is open valve by electromagnetic field to absorb, instantly lose electric valve will shut down.
Decouple of decoupling type solenoid valve, electric valve, high sensitivity, fast. Because with dc low-voltage electricity, there is a little interference or unstable voltage can produce misoperation, affect the normal production. Electric butterfly valve, low price, easy to make a large diameter, the gate valve opening and closing speed is fast, the solenoid valve is slow; Electromagnetic valve flow resistance is small, the gate valve; Sealing the solenoid valve and gate valve is bad, and because the sealing isolation width is small, rapid opening and closing speed impact cause lack of opening and closing or overshoot phenomenon. For electric gate valve, the price is relatively high electric butterfly valve, small flow resistance, good sealing, but speed is slow, can not meet the requirements of emergency cut off. For electric ball valves, small flow resistance, good sealing, but the opening and closing speed slower. RKQ type emergency cut off set the advantages of the ball valve, the electric ball valve opening and closing time is 3. 75 s, the structure design has the anti-static and fire prevention function, but with gas leakage alarm, fan, such as equipment interlocking, good use effect.
(3) gas check valve
Gas ChuPeiZhan compressor need to configure the check valve, prevent gas back into the compressor. General gas check valve plate are the main disadvantages of vibration with the reciprocating movement of the compressor, and the body collision occurs a lot of noise, easy to damage the valve plate; Another poor sealing. Type RH series gas check valve well solve these problems, the use effect is good, maximum nominal diameter of 800 mm.
(1) and underground pipe network medium voltage class B, it is recommended to use directly buried RZ series parallel double ram gray cast iron gate valves or parallel double ram RQZ series ductile iron gate valve.
(2) the underground pipe network medium voltage grade A and the following, it is recommended to use direct buried RZ, RQZ series parallel double sluice gate or TRZ resilient seal gate valve series.
(3) under the underground pipe network pressure B, it is recommended to use direct buried TRZ resilient seal gate valve and fixed gas ball valve series.
(4) underground pipe network pressure A level and above, it is recommended to use fixed ball gas ball valve and all welded ball valve.
5 ChuPeiZhan or ground equipment pressure in 0. 4 MPa, below DN 500 mm above the valves, as far as possible use gate, can reduce the cost.
Level 6 on the pressure regulating device and part of the city, the pressure system is relatively low (below 0. 4 MPa) RZ as recommended or RQZ series parallel double gate valve, also can use gas ball valve floating ball; When the pressure is greater than 0. 8 MPa available fixed gas ball valves and ball TRZ resilient seal gate valve.
All landowners in regulating box due to space limitations, must choose butterfly valve should be use more eccentric butterfly valves with high quality, sealing material chooses ptfe or hard seal.
End gas underground kitchen with large air conditioning, gas boiler, burner using pipe gas leakage alarm system should be set up and emergency cut-off electric ball valves, cut off the gas source, gas leakage, as to ensure safety.