A, the classification of the valve:
There are many kinds of valves, and there are many classification methods: the following are introduced according to purpose, pressure, working temperature of medium, operation mode and general classification.
(1) Block valve: it is mainly used to block and conduct the flow of medium. Such valves include: gate valves, globe valves, diaphragm valves, plug valves, ball valves, butterfly valves, etc.
(2) Regulating valve: it is mainly used to regulate the flow and pressure of medium, including regulating valve, throttle valve and pressure reducing valve.
(3) Check valve: it is mainly used to prevent the medium from flowing back, including check valves with various structures.
(4) Diverter valve: used to distribute, separate or mix media, including distribution valves and traps with various structures.
(5) Safety valve: used for system overpressure safety protection, including various types of safety valves.
(2), according to the pressure classification:
(1) low-pressure valve: nominal pressure PN≤ 1.6Mpa.
(2) medium pressure valve: the nominal pressure is 1.6 MPa < pn ≤ 6.4 MPa.
(3) High pressure valve: the nominal pressure is 6.4 MPa < PN ≤ 100 MPa.
(4) Ultra-high pressure valve: nominal pressure PN≥ 100Mpa.
(3), according to the working temperature of the medium classification:
(1) Normal temperature valve: -40℃≤t≤ 120℃.
(2) Medium temperature valve: 120℃≤t≤450℃.
(3) High temperature valve: t≥450℃.
(4) Low temperature valve:-100℃≤t≤-40℃.
(5) Ultra-low temperature valve: t≤- 100℃.
(4), according to the operation mode classification:
It is divided into manual valve, pneumatic valve, hydraulic valve and electric valve.
(5), general classification:
This classification method is divided according to the working principle and purpose, and also according to the structure, which is a commonly used classification method at present. Generally divided into: gate valve, globe valve, throttle valve, ball valve, butterfly valve, diaphragm valve, plug valve, check valve, safety valve, self-operated pressure regulating valve, steam trap, etc.
Second, the valve model preparation method:
According to the compiling method of valve model, the valve model is divided into seven units.
Three, the structural characteristics and application of commonly used valves:
(a), gate valve:
Gate valve refers to the valve whose opening and closing body (gate) is driven by the valve stem and moves up and down along the sealing surface of the valve seat, which can connect or cut off the fluid channel. Gate valve has small flow resistance and labor-saving opening and closing, and is widely used for opening and closing various medium pipelines. When the gate valve is partially opened, eddy current is generated behind the gate, which is easy to cause erosion and vibration of the gate, damage the sealing surface of the valve seat and make maintenance difficult. Therefore, gate valves are generally not used for throttling.
1, structural characteristics of gate valve:
Gate valve consists of lower valve body, upper valve cover, gate, valve stem, handwheel, sealing ring and other parts.
(1) air duct: divided into wedge-shaped rigid single air duct, wedge-shaped elastic single air duct, wedge-shaped double air duct and double air duct.
(2) Valve stem: distinguish between valve stem and concealed rod. Opening lever means that the valve stem rises and falls with the opening or closing of the gate; The hidden rod is that the valve stem only rotates and rises and falls with the opening and closing of the gate, and the position of the valve stem remains unchanged.
(3) Small-diameter gate valves are generally manual, and large-diameter gate valves can be driven by spur gears or motors.
2, the application scope of gate valve:
Parameter range of gray cast iron and nodular cast iron gate valves: nominal pressure PN0. 1~4.0Mpa, nominal diameter DN50~ 1800mm, flange connection.
Parameter range of steel gate valve: nominal pressure PN0. 1~4.0Mpa, nominal diameter dn50 ~1800 mm. Connection form flange connection.
3. Precautions:
(1) is not suitable for regulating medium pressure and flow.
(2) Suitable for coking occasions, but elastic gate valves and double gate valves are not suitable for application.
(3) For large-diameter or high-pressure gate valves, a bypass valve can be installed to reduce the opening and closing torque of the main gate valve.
(4) For occasions requiring high sealing performance, the valve stem should be sealed with bellows.
4. Advantages and disadvantages:
Advantages: small flow resistance, unlimited medium flow direction and short installation length of valve parts.
Disadvantages: the gate and sealing surface are easy to scratch, and the sealing surface is difficult to repair, which requires the height of valve installation space.
5, common faults and treatment:
(1) packing leakage: the general treatment method is to press the cover tightly or stop the gas to replace the packing.
(2) Treatment of oil cup leakage:
A, oil cup thread leakage-tighten the oil cup or stop refueling and reinstall the oil cup.
B, oil cup mouth leakage-inject grease or replace the oil cup.
(3) Handling method of over-tightening handwheel: add lubricating oil, replace packing and clean the shaft.
(4) Treatment method of internal leakage: blowdown and repair the gate.
6. Daily maintenance: cleaning, turning, draining, injecting lubricating oil and grease.
(2), stop valve and throttle valve:
Globe valve and throttle valve are downward closing valves, and the opening and closing parts (disc) are driven by the valve stem and move up and down along the axis of the valve seat (sealing surface). The structure of stop valve and throttle valve is basically the same, but the shape of disc is different. The disc of the stop valve is a disc disc; The disc of throttle valve is mostly conical streamline, which is especially suitable for throttling. The cross-sectional area of the channel can be changed to adjust the flow or pressure.
1, structural features of stop valve and throttle valve:
It is mainly composed of valve body, valve cover, valve stem, disc and handwheel.
Advantages and disadvantages of globe valves:
Advantages: good sealing performance and low friction of sealing surface. The phenomenon is not serious, the maintenance is more convenient, and the openness is high. The degree is small, and the flow can be adjusted appropriately.
Disadvantages: large medium flow resistance and long structure. Greater and greater opening force.
2. Precautions:
(1) Stop valves should not be used to adjust the pressure or flow of media. Throttle valves should be used for components that often need to adjust pressure or flow.
(2) Straight-through and DC block valves and throttle valves can be installed on horizontal or vertical intersecting pipelines, and angle block valves and throttle valves should be installed on vertical intersecting pipelines. During installation, it should be noted that the indicated direction of the valve body is consistent with the flow direction of the medium.
(3) When the fluid flows upward through the valve seat, deposits on the valve seat will affect the sealing performance, so it is generally not suitable for fluids with suspended substances.
3, fault and treatment:
(1) The packing leaks tightly, and the gland is pressed tightly, or the gas is stopped and replaced.
(2) The handwheel is too tight to loosen the gland or replace the packing.
(3) Clean and repair the internal leakage of the sealing surface.
4. Daily maintenance: cleaning, turning and adding lubricating oil.
(3), plug valve
Plug valve is a kind of valve with simple structure, small resistance drop and convenient opening and closing.
1, structural characteristics: the opening and closing part of the plug valve is plunger type, and the plug interface and the valve body interface are combined or separated by rotating 90 degrees. Plug valve is mainly composed of valve body, valve plug and packing gland.
2. Precautions:
(1) Straight-through plug valve is mostly used to cut off the flow of medium, and can also be used to adjust the flow or pressure of medium.
(2) Three-way cock and four-way cock are mostly used to change the flow direction of medium or distribute medium.
(3) The plug valve can be installed horizontally or vertically, and the medium flow direction is not restricted.
(4) The cock is equipped with electric, hydraulic or pneumatic operating mechanism, which can be controlled remotely or automatically.
3, common faults and treatment:
(1) oil cup leakage
A, oil cup thread leakage-seal the oil cup.
B, oil cup mouth oil leakage-grease injection; Replace the oil cup.
(2) The handwheel is too tight-oil lubrication; Vent and remove the lower part of the valve body, and adjust the displacement of the jacking wire.
(3) Internal leakage-inject sealing grease to repair the sealing surface.
4. Daily maintenance: cleaning, turning, adding lubricating oil and injecting grease.
(4), ball valve:
I. Manual ball valve
The disc of the ball valve is a sphere with a channel in the middle, and the sphere rotates 90 degrees around its own axis to realize opening and closing. Its performance is similar to that of plug valve, and it has the characteristics of fast opening and closing.
1. Structure of ball valve: The ball valve is mainly composed of valve body, ball, sealing ring, valve stem and driving device.
2, the characteristics of ball valve:
(1) Low flow resistance.
(2) simple structure and small volume.
(3) Good sealing performance.
(4) Convenient operation and quick opening and closing.
(5) Easy to maintain.
(6) At high temperature, the opening and closing torque is large and the sealing performance is poor.
3. Application scope of ball valve:
Nominal pressure pn1.6 ~ 32.0 MPa; Nominal diameter dn10 ~ 700 mm; Working temperature t≤200℃.
4. Precautions:
(1) Ball valves are usually used in situations where rapid opening and closing or low resistance is required. It can be used in water, gasoline and other media, as well as in the pipeline of slurry and viscous liquid. Ball valves can also be used for high pressure pipelines and low pressure drop pipelines.
(2) Ball valves are generally not used for throttling because throttling may cause damage to seals or spheres. Full-port ball valve is not suitable for regulating flow.
5, common faults and treatment:
(1) Oil cup leaks.
A, oil cup thread leakage-seal the oil cup.
B, oil cup mouth oil leakage-grease injection; Replace the oil cup.
(2) The handwheel is too tight-turn the valve screw; Reduce the pressure difference before and after the valve; Check the drive worm gear.
(3) Internal leakage-replace the sealing seat and repair the ball.
6. Daily maintenance: cleaning, turning, adding lubricating oil and injecting grease.
Second, the electric ball valve
Electric ball valve is used to control and cut off the airflow, which is generally not suitable for adjustment. Therefore, its state should be fully open or fully closed. Ball valves are installed in the inlet and outlet, pig transceiver and some off-site bypass processes. Ball valve has good reliability in valve seat, automatic pressure relief, fire prevention, sealing design and material selection. The connection mode is flange butt joint, and the actuator is electric actuator.
1, common faults and treatment:
(1) oil cup leakage
A, oil cup thread leakage tight oil cup.
B, oil cup mouth leakage injection grease; Replace the oil cup.
(2) The handwheel is too tight to turn the valve screw.
(3) Internal leakage and sewage discharge; Repair the sphere.
2. Daily maintenance: cleaning, turning, draining, injecting lubricating oil and grease.
(5) Throttle cut-off vent valve and drain valve:
I. FJ4 1Y series throttling stop vent valves:
FJ4 1 throttle cut-off vent valve is a new type of high sealing throttle cut-off vent valve. It has many advantages, such as reliable sealing, corrosion resistance, long service life (several times higher than that of general throttle stop vent valve), high degree of standardization and generalization, and obvious energy-saving effect. It is widely used in petroleum, natural gas, chemical industry and electric power industry.
1, performance specification:
1. 1 Applicable media: petroleum, purified natural gas, general sour natural gas, city gas and various non-corrosive media.
1.2 nominal pressure PN (MPa): 2.5, 4.0, 6.4, 10.0, 16.0, 32.0.
1.3 nominal diameter dn (mm): 25, 40, 50, 65, 80, 100, 125, 150, 200, 250.
1.4 medium temperature: -29- 130℃.
2. Model description
3. Working principle:
3. 1 working principle: FJ4 1Y throttle stop vent valve adopts double-quality (soft and hard) seal, and the structure of separating throttle and seal greatly improves the sealing performance and service life of the valve.
3.2 Double-mass seal: FJ4 1Y throttle stop vent valve has a soft seal on the valve seat in addition to the hard seal pair, and the valve core closely adheres to the two sets of seal pairs on the valve seat under the action of stem thrust and medium pressure to form a double-mass seal.
3.3 Throttling function: The throttling part of FJ4 1Y throttling stop vent valve is located on the throttling channel formed by the circumferential opening of the spool sleeve and the plunger-shaped spool. When the valve is slightly opened, the valve core leaves the soft sealing pair of the valve seat. At this time, only a small amount of fluid enters the outlet end of the valve through the gap between the spool sleeve and the spool.
When the valve continues to open, the circumferential opening of the spool sleeve and the end of the plunger-shaped spool form a throttling hole, where the fluid throttles into the outlet end of the valve. When the valve is fully opened, the fluid flows evenly to the outlet through the circumferential opening of the spool sleeve, and the resistance loss is small when the valve is fully opened.
4. Installation requirements:
4. 1 This valve is a normally closed valve, which is used for emergency venting and other normally closed working conditions.
4.2 This valve can be installed outdoors, and the medium flows in one direction.
4.3 The installation position shall ensure sufficient space for maintenance, inspection and operation.
4.4 During installation, disassembly and debugging, do not damage the seals and seals.
5, common faults and treatment
(1) The packing gland does not leak or needs to be stopped and replaced.
(2) The handwheel is too tight-loosen the gland or replace the packing.
(3) Internal leakage-clean and repair the sealing surface.
6. Daily maintenance: cleaning, turning and adding lubricating oil.
(1) Pay attention to the angular seal between the valve body and the valve seat during disassembly inspection. Is the O-ring damaged? If it is damaged, it needs to be replaced.
(2) Regularly fill the trapezoidal thread of the valve stem and the screw sleeve with grease.
Second, the valve sleeve type sewage valve
Valve sleeve sewage valve adopts the form of nozzle and valve sleeve window opening. In order to meet the needs of throttling, decompression and pollution discharge of pipeline equipment, the valve core and valve seat adopt soft and hard double sealing pairs, the soft seal is recessed into the inner cavity of the valve core, and the gap between the valve core sleeve and the valve seat channel matches the change of medium flow direction, so that the sealing surfaces of the valve core and valve seat have self-cleaning function.
The valve has the advantages of light and flexible opening, corrosion resistance, long service life, high degree of standardization, obvious energy-saving effect, remarkable throttling and sewage discharge functions and so on. It is widely used in direct sewage discharge of oil and gas pipeline gathering and transportation devices, and can meet the application under high parameter technical conditions.
1, performance specification:
1. 1 Applicable media: petroleum, purified natural gas, general sour natural gas, city gas and various non-corrosive media.
1.2 nominal pressure PN (MPa): 2.5, 4.0, 6.4, 10.0, 16.0.
1.3 nominal diameter dn (mm): 25, 40, 50, 65, 80, 100, 125, 150, 200, 250.
1.4 medium temperature: -29- 130℃.
2. Model description
3. Working principle:
3. 1 closed state: the hard seal of the valve core is pressed on the conical surface of the valve seat boss to form a hard seal; At the same time, the fluoroplastic end face embedded in the valve core cavity is pressed against the end face of the valve seat to form a second soft seal. Soft and hard double sealing ensures the leakage of gas-liquid medium "0".
3.2 Throttle and blowdown state: the soft and hard double seal of the valve core leaves the valve seat, and the valve slowly opens. The medium and impurities in the pipeline are throttled through the nozzle and valve seat flow passage, and then discharged through the window of the valve sleeve. The sealing surface of valve core and valve seat changes the flow direction of medium by using the oblique angle of sleeve pad, which has self-cleaning function, so that the sealing pair does not carry impurities.
3.3 Discharge closed state: After the medium in the pipeline is discharged, the valve is closed, and the oblique angle of the sleeve pad enters the valve seat channel, which increases the flow resistance coefficient and speeds up the flow rate. The oblique angle changes the flow direction of the medium, and the radial force of the medium on the end face of the valve seat increases, thus purging the sealing surface of the valve seat. When the valve core sealing pair is close to the valve seat, the mating gap between the sleeve pad and the valve seat channel prevents larger particles from flowing to the sealing pair. In addition, with the further increase of the flow rate and the purging of the lateral force of the medium, when the sealing pair of the valve has been completely cleaned
4, use requirements:
(1) This valve is used for oil and gas blowdown and venting.
(2) The valve can be installed outdoors, and the medium flows in one direction.
(3) The installation position shall ensure sufficient space for maintenance, inspection and operation.
(4) During installation, disassembly and debugging, do not damage the seals and seals.
5, common faults and treatment:
(1) Replace the packing gland or gas plug.
(2) The handwheel is too tight-loosen the gland or replace the packing.
(3) Internal leakage-clean tetrafluoroethylene gasket or replace it.
6. Daily maintenance: cleaning, turning and adding lubricating oil.
(6) Check valve:
Check valve, also known as one-way valve and one-way valve, is a kind of check valve, which is used to limit the one-way flow of airflow and prevent reverse flow. There are two kinds: lifting and swinging. The check valve of our company is a swing check valve. Its structural characteristics and working principle are as follows:
1. structural features: it consists of valve body, valve cover, disc, sealing ring, rocker arm, etc.
2. Principle of action: Fluid enters the valve from the lower end. When the thrust generated by the pressure difference between the fluid before and after the valve is greater than the gravity of the disc, the fluid pushes the disc away, making the disc rotate along the rocker and letting the fluid pass. When the fluid flows backwards, the pressure at the outlet end is greater than that at the inlet end. Under the action of gravity and pressure difference, the disc moves backwards along the rocker to prevent the fluid from flowing backwards.
3. Precautions:
When installing the valve, we must pay attention to the direction of the inlet and outlet, so that the flow direction of the disc is consistent with the flow direction of the fluid.
4, common faults and treatment:
(1) Repair and installation of disc falling off.
(2) The seal is lax. Check and replace sealing ring.
(7) Safety valve:
The valve is used in pressurizing equipment and pipelines of gas transmission stations. When the equipment and pipeline have accidents due to overpressure, the safety valve will automatically open to discharge the natural gas in the equipment and release the pressure to a normal state.
1. structural features: it is composed of main parts such as valve body, valve stem, valve disc, valve seat, adjusting screw and spring. It is divided into lever type, spring type and pilot type. The gas transmission station of our company mainly adopts spring type and pilot type.
2. Principle of action:
Spring-type safety valve: The spring-type safety valve uses the pre-tightening force of the spring to balance the pressure of the fluid in the equipment. When the fluid pressure in the device exceeds the pressure of the safety valve spring, the valve disc is pushed open to release the pressure. When the fluid pressure in the device is lower than the pressure of the spring, the safety valve will automatically close.
By adjusting the screw to adjust the tightness of the spring, different pre-tightening force given values can be obtained, which can meet the requirements of different equipment and different allowable working pressures. Spring-type safety valves can be divided into fully closed, semi-closed and open types according to different service conditions. According to the different opening heights of valve discs, they can be divided into fully open type and slightly open type, and gas transmission stations mostly adopt fully open type and fully closed type.
Pilot safety valve: it consists of main valve and auxiliary valve. Media pressure and spring pressure act on the main disk at the same time. When overpressure occurs, the auxiliary disc opens first, which causes the main valve to open. Mainly used in large-caliber and high-pressure occasions.
(8) emergency cut-off valve:
The gas safety cut-off valve is applied to the gas transmission and distribution system for emergency cut-off protection, and has the function of monitoring the overpressure cut-off of gas pressure (which can be reset manually). When the system force is higher or lower than a certain pressure value, the cut-off valve can cut off quickly and urgently to achieve the purpose of safe use.
1, structural features:
It consists of main valve, tripping mechanism and sensor. High action precision and fast response speed; Using the pressure of the pipe network itself, no extra energy is needed; Overvoltage automatic cut-off; Simple installation and debugging, convenient operation and maintenance; It can work normally in dirty gas medium.
2. Applicable temperament: natural gas, coal gas, liquefied petroleum gas and other non-corrosive gases.
3. Main technical parameters:
Working pressure range: P≤ 1.6Mpa (or P≤4.0Mpa).
Working pressure range: 0.001MPa-1.2mpa.
Working temperature: -20~60℃.
Pipe diameter series: DN50, DN80, DN 100, DN 150, DN200, DN250.
4. Description of model preparation:
Example: AQZ 12G stands for direct-acting overpressure safety cut-off valve, with nominal diameter DN50 and working pressure grade 1.
5. Principle of action: When the signal pressure is abnormal, exceeding (overpressure) or lower than (pressure loss type) the pressure setting value, the pneumatic diaphragm of the sensor drives the bump to move, which makes the trip mechanism move and the main valve close quickly, thus protecting downstream equipment such as voltage regulator and metering instrument.
6. Reset operation of cut-off valve:
When the cut-off valve is cut off and closed, the cause of overpressure should be checked, and the reset operation can be carried out only after the solution is solved. The method is as follows:
(1) Close the water inlet valve.
(2) Check whether the outlet pressure value is within the normal range, and proceed to the next operation after it is normal.
(3) Hold the reset handle by hand and press it down to a horizontal state to confirm that the tripping mechanism has been tightened.
(4) Open the inlet valve slowly. If it is opened too fast, the cut-off valve may be cut off again.
7, common faults and treatment:
(1) It is not strictly closed after cutting, and the impurities on the gasket are cleaned up; Replace the sealing gasket.
(2) the action is not sensitive, and the collision position is adjusted; Properly lubricate to reduce friction.
(3) The tripping mechanism is not tightened, and the gas is discharged through the test cock; Replace the spring; Resume manual closing of the knob.
8, daily maintenance:
Check the sensitivity of tripping mechanism and sensor bump. If it is not flexible, lubricate it.