How to install pipe valve and overhaul?
The function of the valve is to control or adjust the flow state of the fluid. In the construction process, the quality of valve installation directly affects the normal operation in the future, so we must pay attention to it.
Five main points of valve installation
Direction and position
Many valves have directionality, such as stop valves, throttle valves, pressure reducing valves, check valves, etc. If they are installed reversely, it will affect the use effect and life (such as throttle valves), or it does not work at all (such as a pressure reducing valve) or even causes danger (such as a check valve). General valve, with direction mark on the valve body. In case of failure, it should be identified correctly according to the working principle of the valve.
The valve chamber of the stop valve is asymmetrical on the right and left sides, and the fluid needs to pass through the valve port from bottom to top, so that the fluid resistance is small (determined by the shape), and the opening is labor-saving (because the medium pressure is upward), after closing, the medium does not press the stuffing for maintenance, which is why the stop valve cannot be installed in reverse. Other valves also have their own characteristics.
The valve installation location must be convenient for operation. Even if the installation is temporarily more difficult, it should be considered for the long-term work of operators. It is best to get the valve handle wheel and the chest (generally 1.2 meters away from the operating floor), so that opening and closing the valve is more difficult. The hand wheel of the floor valve should not tilt up to avoid maladjustment of the operation. The room for the operator to stand should also be kept by the valve of the equipment against the wall.
Avoid operating on the sky, especially acid and alkali, toxic media, etc., otherwise it is very unsafe.
Don’t install the gate upside down (hand wheel down), otherwise the medium will stay in the valve cover space for a long time, which will corrode the valve stem easily, and it is forbidden by some process requirements. It is extremely inconvenient to replace the stuffing at the same time. Open bar gate valve, do not install it underground, otherwise it will corrode the exposed valve stem due to humidity.
Lift check valve, make sure its disc is vertical when installing, in order to lift flexibly. When installing the swing check valve, ensure its level of pin shaft so as to screw off. The pressure reducing valve should be installed upright on the horizontal pipe, and it should not be tilted in all directions.
Be careful in installation and construction, and avoid hitting the valve made of brittle materials.
- Carefully check whether the models and specifications of all valves meet the design requirements. According to the valve model and factory manual, check whether they can be applied under the required conditions, and if necessary, make a water pressure or air pressure test.)
- Besides, it is also necessary to check whether the filling is intact, whether the gland Bolt has enough adjustment allowance, and whether the valve stem and the valve plate are nimble, and whether there is stuck and skew. The sealing surface of the valve disc must be tightly closed, and the quality of the thread of the valve connected with thread should be checked. Unqualified valves cannot be installed, and should be stacked or marked separately.)
- Clean the sundries in the valve.
Installation process of valve
- When the valve is lifted, the rope should not be tied to the hand wheel or valve stem, so as not to damage these components, it should be tied to the flange.
- Be sure to clean up the pipeline connected with the valve.
Able to use compressed air to blow off oxidation iron scrap, mud sand, welding slag and other sundries. These sundries not only easily scratch the sealing surface of the valve, but also block the small valve and make it invalid.
When installing the screw valve, the sealing filler (wire linen plus aluminum oil or PTFE) should be wrapped on the thread of the pipe. Do not get into the valve, so as to avoid the deposit of the valve and affect the circulation of the medium.
When installing the flange valve, pay attention to tighten the bolt symmetrically and evenly. The valve flange and pipe flange must be parallel, and the gap is reasonable to avoid excessive pressure or even cracking of the valve. For brittle materials and valves with low strength, special attention should be paid. The valve to be welded with the pipe should be spot-welded first, and then all the closed parts should be opened, and then welded dead.
Some valves also need external protection, which is heat preservation and cold preservation. Sometimes hot steam pipelines are added in the insulation layer. What kind of valve should be kept warm or cold, depends on production requirements.
In principle, where the medium in the valve reduces the temperature too much, it will affect the production efficiency or freeze the valve, it needs to be insulated or even hot; Where the valve is exposed, when it is unfavorable to production or causes Frost and other adverse phenomena, it is necessary to keep cold. Insulation materials include asbestos, mineral wool, glass wool, perlite, diatomite, vermiculite, etc. Cold insulation materials include cork, perlite, foam, plastic, etc.
Bypass and instrumentation
In addition to necessary protection facilities, some valves also have a bypass and instrument. Bypass installed. It is convenient for maintenance of trap. Other valves also have bypass installed. Whether to install bypass depends on the valve condition, importance and production requirements.
Inventory valve, some of the stuffing is not easy to use, some do not match the use of media, which requires replacement of stuffing.
The valve manufacturing factory cannot consider that the different media of the thousands of different types of media are always filled with ordinary packing, but when using, the packing must be suitable for the media.
When replacing the packing, press it in circles. Each circle of seams is suitable for 45 degrees, and the circle is connected with the circle by 180 degrees. The stuffing height should consider the space for the gland to continue pressing, and now it is necessary to give the appropriate depth of the stuffing room at the lower part of the gland, which can generally be 10-20% of the total depth of the stuffing room. For valves with high requirements, the joint angle is 30 degrees. The joint between the circle and the circle is staggered by 120 degrees.
In addition to the above-mentioned fillers, rubber O-rings can also be used according to specific circumstances (natural rubber is resistant to weak alkali below 60 degrees Celsius, nitrile rubber is resistant to oil crystals below 80 degrees Celsius, fluorine rubber is resistant to a variety of corrosive media below 150 degrees celsius three-piece laminated PTFE ring (resistance to 200 degrees celsius strong corrosion medium nylon bowl ring (resistance to ammonia, alkali at 120 degrees celsius) and other formed fillers.
Outside the packing of ordinary asbestos packing, wrap a layer of teflon tape, which can improve the sealing effect and reduce the electrochemical corrosion of the valve stem. When pressing the seasoning, turn the valve rod at the same time to keep it uniform around and prevent it from being too dead. Tighten the gland to be even and not tilt.
14 major taboos for Valve installation
Taboo 1: the main materials, equipments and products used in construction are lack of technical quality identification documents or product certificates which conform to the current national or ministerial standards.
Consequences: The project quality is not up to standard, there are hidden dangers, can not be delivered on time, must be reworked and repaired; Cause delay in construction period, increase labor and material investment.
Measures: the main materials, equipment and products used in water supply and drainage and heating and sanitation projects shall have technical quality appraisal documents or product certificates that meet the national or ministerial standards, model, specification, national quality standard code, factory date, name and location of the manufacturer, factory product inspection certificate or code.
Taboo 2: do not carry out necessary quality inspection according to regulations before valve installation.
Consequences: during the operation of the system, the valve switch is not flexible, the closing is not tight, and the phenomenon of water leakage (steam) occurs, causing rework and repair, and even affecting the normal water supply (steam).
Measures: before installing the valve, the pressure strength and leakproofness test should be done. The test should sample 10% of the number of each batch (same brand, same specification, same model), and no less than one. For the closed-circuit valves installed on the main pipe with cutting off function, they should be tested for intensity and leakproofness one by one. The intensity and leakproofness test pressure of the valve shall comply with the provisions of the “code for acceptance of construction quality of building water supply and drainage and Heating Engineering” (GB 50242-2002).
Taboo 3: the specification and model of the valve installed do not meet the design requirements. For example, the nominal pressure of the valve is less than the system test pressure; The water supply branch pipe adopts the gate valve when the pipe diameter is less than or equal to 50mm; The shut-off valve is adopted for the dry and vertical pipes of the hot water heating; The suction pipe.
Consequences: affect the normal opening and closing of the valve and adjust the resistance, pressure and other functions. Even cause the system operation, the valve is damaged and forced to repair.
Measures: be familiar with the application scope of various valves and choose the specifications and types of valves according to the design requirements. The nominal pressure of the valve shall meet the requirements of the system test pressure. According to the requirements of construction specification: stop valve should be used when the pipe diameter of water supply branch pipe is less than or equal to 50mm; When the pipe diameter is greater than 50mm, gate valve should be used. Hot water heating dry, vertical control valve should use the gate valve, fire pump suction pipe should not use the butterfly valve.
Taboo 4: Valve installation method is wrong. For example, the stop valve or check valve has the opposite water (steam) flow direction and the sign, and the valve stem should be installed downward, and the check valve installed horizontally should be installed vertically. There is no open or closed space for the open pole gate valve or the butterfly valve handle, the valve stem of the concealed valve does not face the inspection door.
Consequences: the valve fails, the switch is difficult to repair, and the valve stem is often leaking.
Measures: install the valve strictly according to the valve installation instruction. The open lever gate valve should keep the valve stem extended to the opening height. The butterfly valve should fully consider the rotation space of the handle. The concealed valve should not only set an inspection door that meets the opening and closing requirements of the valve, but also face the inspection door.
Taboo 5: use ordinary valve flange for butterfly valve flange plate.
Consequences: the size of flange of butterfly valve is different from that of ordinary valve. Some flanges have small inner diameter, while the disc of butterfly valve is large, which causes failure to open or rigid opening and damage to the valve.
Measures: process the flange plate according to the actual size of the butterfly valve flange.
Taboo 6: There is no reserved hole and embedded parts in the construction of building structure, or the size of reserved hole is too small and the embedded parts are not marked.
Consequences: in the construction of the warm-up project, the building structure is dug and the forced steel bar is even cut off, which affects the safety performance of the building.
Measures: carefully familiar with the construction drawings of the warm and away project, and actively and conscientiously cooperate with the construction of the building structure to reserve holes and embedded parts according to the requirements of the design and the construction specifications.
Taboo 7: when welding the pipe, the misalignment behind the butt joint pipe is not in a single central line, the butt joint does not leave a gap, the thick-walled pipe does not shovel the groove, and the width and height of the weld joint do not meet the construction specifications.
Consequences: The misalignment of the pipe does not directly affect the welding quality and impression quality. The matching does not leave the gap, and the thick-walled pipes do not shovel the groove. When the width and height of the welding seam do not meet the requirements, the welding does not meet the requirements.
Taboo 8: the pipeline is directly buried on the frozen soil and loose soil without treatment, and the piping pier spacing and position is improper, even in the form of dry code bricks.
Consequence: The pipe will be damaged during the compaction of backfill soil due to unstable support, which will result in rework and repair.
Measures: pipelines cannot be buried on frozen soil and loose soil without treatment, the spacing of Pier should conform to the requirements of construction specifications, and the support cushion should be firm, especially at the interface of pipelines, which should not bear the shear force. The brick pier should be built with cement mortar to ensure integrity and firmness.
Taboo 9: the material of the expansion bolt of the fixed pipeline support is inferior. The hole size of the expansion bolt installed is too large or the expansion bolt is installed on a brick wall or even a light weight wall.
Consequences: the pipe bracket is loose, the pipeline is deformed, and even falls off.
Measures: the expansion bolts must choose qualified products, and samples should be taken when necessary. The aperture of the expansion bolts should not be greater than the diameter of the expansion bolts. The expansion bolts should be applied to concrete structures.
Taboo 10: the strength of flange plate and gasket connected by pipe is not enough, and the connecting bolt has short or thin diameter. Thermal pipeline uses rubber pads, cold water pipeline uses asbestos pads, and uses double-layer pads or inclined pads, flange pads into the tube.
Consequences: the flange connection is not tight, or even damaged, and leakage occurs. The flange gasket enters the tube, which will increase the water flow resistance.
Measures: flanges and gaskets used for pipelines must meet the requirements of design working pressure of pipelines. Flange gaskets for heating and hot water supply pipelines should use rubber asbestos gaskets; And flange gaskets for water supply and drainage pipelines should use rubber gaskets.
The gasket of flange shall not flash into the tube, and its outer circle is better to the flange bolt hole. Inclined pads or several gaskets should not be placed in the middle of the flange. The diameter of the bolt of the connecting flange should be less than 2mm than the diameter of the flange plate.
Taboo 11: when the water pressure strength test and leakproofness test of the piping system, only observe the pressure value and water level change, and check the leakage not enough.
Consequences: leakage occurs after the operation of the pipeline system, affecting the normal use.
Measures: when the piping system is tested according to the design requirements and construction specifications, in addition to recording the pressure value or water level change within the specified time, it is necessary to carefully check whether there is leakage.
Taboos 12: the pipes of sewage, rainwater and condensate shall be concealed without the water-closing test.
Consequences: water leakage may be caused and user losses may be caused.
Measures: check and accept the work of the closed-water test strictly according to the specification. Underground burying, ceiling, pipe room, etc., concealed sewage, rainwater, condensate pipes, etc. should be met to ensure no infiltration and no leakage.
Taboo 13: The Flushing is not serious before the completion of the pipeline system, and the flow and speed can not meet the requirements of pipeline flushing. Even water pressure strength test drain instead of flushing.
Consequence: if the water quality cannot meet the operation requirements of the pipeline system, it will often cause the reduction or blockage of the pipeline section.
Measures: use the maximum juice flow in the system or the water flow velocity which should not be less than 3m/s for rinsing. It is qualified that the color and transparency of the water at the outlet is visually consistent with that of the inlet water.
Taboo 14: during winter construction, water pressure test shall be carried out at negative temperature.
Consequences: as the pipe freezes quickly during the hydraulic pressure test, the pipe freezes.
Measures: try to conduct a hydraulic test before winter application, and blow the water clean after the pressure test, especially the water in the valve must be cleaned up, otherwise the valve will crack and crack. The project must carry out a hydraulic pressure test in winter, and the water should be blown clean after the pressure test. When the hydraulic pressure test cannot be carried out, the test can be carried out by compressed air.
Matters needing attention in valve installation.
- 1. The open stem cannot be directly laid underground to prevent the stem from being rusted, and can only be installed in a trench with a cover. The valve should be installed in a location where is convenient for operation, inspection, disassembly, maintenance and operation.
- 2. Throwing the valve is not allowed to avoid damage and deformation. When stacking, carbon steel valves, stainless steel valves and non-ferrous metal valves should be separated. When hoisting the valve, the steel wire rope should be tied to the flange between the valve body and the valve cover, in case of damaging the valve stem and the hand wheel.
- 3. The valve installation position should not hinder the disassembly, assembly, maintenance and operation of equipment, pipelines and the valve itself. The installation height should be convenient for operation and maintenance. Generally, the operation handle of the valve should be 1-below the ground. When the valves which have more operations must be installed at more than 1.8m from the operation surface, a fixed operation platform should be set up. When the valves must be installed at the above or below the operation surface (public number: pump housekeeper), the extension rod should be set or the valve stem should be installed horizontally, and a handwheel with a transmission device or a remote operation device should be installed at the same time. The included angle of the axis of the valve transmission device should be no more than 30 °, and its joint should be flexible to rotate, easy to use during operation, and accurate indication. The valve transmission device with thermal displacement should have compensation measures.
- 4. It is better to install the valve vertically up or within the upper semicircle, but not down. The valve stem and hand wheel on the vertical pipe must be installed along the direction of the operation circuit. When conditions are available, the valve should be installed as intensively as possible for easy operation. Valves on the pipelines of tower area that are 4m above the ground should not be set outside the platform, so as to be convenient for installation and operation.
- 5. For directional valve, the installation direction should be determined according to the medium flow direction of the pipeline. If the stop valve is installed, the medium should be made from the bottom of the cabinet plate to the top, commonly known as low-entry and high-end. When installing the cock and the gate valve, the media is allowed to flow out from either end. When installing the check valve, special attention must be paid to the flow direction of the medium to ensure that the valve plate can open automatically. In important occasions, arrows should be clearly marked outside the valve to indicate the flow direction of the medium. For the swing check valve, ensure that the pivot of the pin plate is installed in the horizontal position. For lift check valve, the center line of the valve plate should be ensured to be perpendicular to the horizontal plane.
- 6. For valves with special requirements, be familiar with the installation requirements. For example, when installing lever safety valve and pressure reducing valve, the center line of valve plate must be perpendicular to the horizontal plane, and correction must be made when tilt is found.
- 7. When installing the union and the valve with threaded connection on the pipeline, it is necessary to install the union near the valve for easy disassembly.
- 8. The cut-off valve should be set when the auxiliary system pipeline enters the workshop. When the workshop stops for maintenance, it can be cut off from the total pipeline. The installation height of these valves is generally higher, and they should be arranged together as much as possible so as to set up a fixed operation platform.
- 9. When installing the valve connected with flange, it is necessary to ensure that the two flange end face connected with it is parallel and coaxial with the valve flange. Especially when installing valves made of cast iron and other materials that are relatively brittle, the damage of the valves caused by incorrect installation position and uneven stress should be avoided. When tightening the flange bolt, the method of symmetry or cross should be adopted to tighten the flange bolt gradually in several times.
- 10. Before the installation of high-pressure valve, the product certificate and test records must be reviewed. High-pressure valves are mostly angle valves, which are often connected by two in series. When opening, the starting force is large. The valve frame must be set to support the valve and reduce the starting stress. Its installation height is 0.6-1.2m.
- 11. The tube joints of pumps, heat exchangers, towers and containers should not bear the weight of valves and pipelines. The valves with nominal diameter dn>80mm should be added with supports.
- 12. Lining, spraying and non-metallic materials the door itself is of high quality and low strength. In addition to considering the process requirements, it should be arranged as centrally as possible to facilitate the design of the valve frame. Even a single valve should be fixed on the valve frame. When installing heavy-duty valves on horizontal pipes, brackets should be considered to be installed on both sides of the valve.
- 13. Install the valve connected with thread to ensure the integrity of the thread. Fill should be selected according to working conditions, and the position of the valve stem should meet the installation requirements when it is screwed up. When tightening, a wrench must be used to hold tightly on the hexagonal body of the valve at one end of the pipe to ensure that the valve body is not deformed or damaged. Valves connected by flanges or threads shall be installed in a closed state.
- 14. Argon arc welding should be used to ensure the inside is smooth and clean. When welding, the valve should not be closed to prevent overheating and deformation of the sealing surface. If the sealing material is not resistant to high temperature, remove the sealing material before welding to prevent the welding high temperature from damaging the sealing material.
- 15. The net distance between the hand wheels of the valves on the side-by-side pipelines shall not be less than 100mm. In order to reduce the distance between the pipelines, the valves arranged side by side should be arranged alternately.
- 16. Before the positioning of the low temperature valve, try to do the opening and closing test under the cold state, and there is no clamping phenomenon.
- 17. The joint of the safety valve should have an elbow (or three-way and other accessories) to avoid the direct impact of the fluid on the valve; In addition, to ensure that the safety valve does not frost when working, so as not to fail during work.
- 18. It is strictly prohibited to climb the valve stem as scaffold when installing the valve.
- 19. High temperature valve above 200 ℃, because the valve is installed at room temperature, and after normal use, the temperature rises, the valve bolt is heated and the gap is enlarged, so it must be tightened again, called “hot tight”, operators should pay attention to this work, otherwise it is prone to valve leakage and other incidents.
- 20. When it is cold in winter, the water valve should be closed and stopped for a long time, and the water behind the valve should be removed. After the steam stop, condensate water should also be removed. There is such a drain switch at the bottom of the valve, which can be turned on for drainage.
- 21. Non-metallic valves, some are hard and brittle, and some are of low strength. When operating, the opening and closing force cannot be too large, especially not strong. Also pay attention to the demolition of objects.
- 22. When installing the stop valve, the flow direction should be consistent with the arrow marked on the valve body (it cannot be installed reversely), so that when the valve is closed, the pressure is applied to the cone on the top of the valve, and the filling is not loaded. However, for those valves (such as heating valves) which are not often open or closed and need to be strictly ensured not to leak in the closed state, they can be deliberately installed reversely according to the requirements, so as to be tightly closed with the help of medium pressure.
- 23. Large-sized gate valves (DN200-500MM) and pneumatic control valves should be installed vertically to prevent leakage caused by large self-weight of the valve core, increasing mechanical wear between the valve core and bushing.
- 23. When tightening the compression screw, the valve should be in a slightly open state to avoid crushing the top sealing surface of the valve.
- 24. After all valves are in place, they should be opened and closed again. Flexible and no clamping is qualified.
- 25. After the large air separation tower turns naked and becomes cold, it conducts pre-tightening on the flange of the connecting valve, so as to prevent the valve from leaking at room temperature and at low temperature of the valve.
- 26. When the new valve is in use, do not press too tight, and do not leak, so as to avoid the pressure of the valve stem of the valve, the accelerated wear, and the difficulty of opening and closing.
- The most important thing is the installation of the valve. The quality of the installation affects the normal operation in the future.
Common faults and causes of general valves
1. Reasons for leakage of stuffing letter and maintenance methods:
|Cause of failure||Maintenance method|
|The filling method is incorrect (such as the whole string is placed)||Correct packing|
|Valve stem deformed or rusty corrosion||Repair or renewal|
|Stuffing aging||Replacement of packing|
|Improper or overviolent operation||Slow opening and slow closing, smooth operation|
2. Reasons for valve stem failure and maintenance methods:
|Cause of failure||Maintenance method|
|Stem damage, corrosion release||Replacement valve|
|Stem Bend||When the valve is not easy to open, do not use long equipment to pry the hand wheel, the twisted valve stem needs to be replaced|
|Valve rod nut tilt||Replace valve parts or valves|
|The open-air valve is rusty||Open valve should strengthen maintenance, regular rotation hand wheel|
3. Causes and maintenance methods of sealing surface leakage:
|Fault cause||Maintenance method|
|Worn sealing surface, light corrosion||Regular grinding|
|Improper closing, poor contact with the sealing surface||Slowly, repeatedly open and close several times|
|STEM is bent, upper and lower sealing surfaces are not centerline||Repair or replacement|
|Impurity cap||Open, remove sundries, then slowly close, add filter if necessary|
|The seal ring does not match tightly with the valve seat and valve Clack||Repair|
|The valve Clack is not firmly connected with the valve stem.||Repair or replacement|
4. Other faults, causes and maintenance methods:
|Fault||Fault cause||Maintenance method|
|Gasket leakage||The gasket material is not suitable or the failure is affected by the medium in daily use||Adopt gaskets suitable for working conditions or replace gaskets|
|Valve cracking||Freeze or screw thread Valve installation with excessive force||Insulation and anti-freezing, uniform and appropriate force during installation|
|Hand wheel damaged||Heavy Object Impact, long rod pry don’t open, inner square hole wear and edge||Avoid impact, uniform force when opening, correct direction, file square hole or replace hand wheel|
|Gland rupture||Uneven force when tightening lid||Symmetric tightening nut|
|Gate failure||The wedge disc is not tightly closed due to corrosion, and the top wedge of the double disc is damaged||Regular grinding, replaced with carbon steel top wedge|
Common faults and causes of automatic valve
1. Common faults, causes, prevention and maintenance of check valves
|Fault||Fault cause||Maintenance method|
|Back medium flow||
1. The sealing surface between the valve core and the valve seat is damaged.
2. There is dirt between the valve core and valve seat.
1. Grinding sealing surface.
2. Remove dirt.
|Spool does not open||
1. The sealing surface is stuck by scale.
2. The shaft is rusted.
1. Remove scale.
2. Polish rust to make it flexible.
|Valve Clack||The medium pressure before and after the valve is in a “saw” state close to balance, making the valve Clack made of brittle material flick frequently||Flexible material valve Clack|
2. Common faults, causes, prevention and repair of trap
|Fault||Fault cause||Maintenance method|
1. Steam pressure is too low.
2. Steam and condensate water do not enter the trap.
3. The pontoon type is too light.
4. The floating stem and casing are stuck.
5. Valve hole or channel is blocked.
6. The thermostatic valve core is broken and the valve hole is blocked.
1. Adjust steam pressure.
2. Check whether the Steam pipeline valve is closed and blocked.
3. Add appropriate amount or replace the float.
4. Overhaul or replace to make it flexible.
5. Remove blocked debris and install a filter in front of the valve.
6. Replace the valve core.
1. Valve core and valve seat are worn and leaking steam.
2. The drain hole cannot be closed by itself.
3. The float cylinder is small in size and cannot float.
1. Grinding sealing surface.
2. Check whether there is dirt blockage.
3. Appropriately increase the volume of the buoy.
|Continuous working temperature drop||
1. Displacement is lower than condensate water.
2. Increase the amount of condensate water in the pipeline.
1. Replace the appropriate trap.
2. Install a trap.
3. Common faults, causes, prevention and maintenance of pressure reducing valve
|Fault||Fault cause||Maintenance method|
|Unstable pressure behind valve||
1. The pulse type is the improper selection of valve diameter, and the medium pressure difference at both ends is large.
2. Improper selection of spring-type adjustable spring.
1. Replace the appropriate pressure reducing valve.
2. Replace the appropriate adjustment spring.
1. The control channel is blocked by sundries.
2. The rust inside the piston gets stuck and cannot move down at the highest position.
1. Remove sundries and install the filter in front of the valve.
2. Overhaul the piston to make it flexible.
1. The piston is stuck in a certain position.
2. The lower spring of the main valve disc is broken.
3. The valve handle of the pulse valve is stuck at the close position.
4. There is dirt stuck or serious corrosion between the sealing surface of the main valve disc and the valve seat.
5. Film failure.
1. Overhaul the piston to make it flexible.
2. Replace the spring.
3. Overhaul to make it flexible.
4. Remove dirt and grind the sealing surface regularly.
5. Replace the diaphragm.
|The pressure behind the valve cannot be adjusted||
1. The regulating spring fails.
2. The cap leaks and cannot maintain pressure.
3. Piston, cylinder wear or corrosion.
4. The valve body is full of condensate water.
1. Replace the adjustment spring.
2. Timely maintenance and replacement of gasket.
3. Overhaul the cylinder and replace the piston ring.
4. Loosen the plug and drain the condensed water.
4. Common failures, causes, prevention and repair of safety valves
|Fault||Fault cause||Maintenance method|
|Sealing surface leakage||
1. There is dirt or wear on the sealing surface of the valve core and the valve seat.
2. The center line of the valve stem is not correct.
1. Remove dirt or grinding seal.
2. Correct the center line of the stem.
|Do not open under working pressure||
1. The lever is stuck or the pin is rusted.
2. Lever-type heavy hammer is moved.
3. Spring type Spring is heated and deformed or failed.
4. The spool sticks to the valve seat.
1. Overhaul lever or pin.
2. Adjust the weight position.
3. Replace the spring.
4. Do regular exhaust test.
|Opens when no working pressure||
1. The hammer of the lever moves inward.
2. The spring type is not elastic enough.
1. Adjust the weight position.
2. Tighten or replace the spring.
|Valve core does not close automatically after opening||
1. Lever-type lever deviation.
2. Spring Spring bending.
3. Valve core or valve stem is not correct.
1. Maintenance lever.
2. Adjust the spring.
3. Adjust the valve core or valve rod.
Overhaul of common valves
During the installation and use of the valve, due to manufacturing quality and wear and other reasons, the valve is prone to leakage and loose closure.
1. Gland leak repair
(1) Leakage maintenance of small bonnet;
(2) Leakage maintenance of larger valve cover.
2. Can not be opened or opened without steam or water
- (1) Gate valve;
- (2) Stop valve;
- (3) The valve or pipeline is blocked.
3. Can’t be kept or closed
- (1) Lax: it may be due to the stuck between the valve seat and valve core, or the valve seat, valve core is scratched, resulting in the valve can not be closed.
- (2) Can’t be closed: when opening the valve, it is too hard to open the head.
Source: Network Arrangement – China Valves Manufacturer – Yaang Pipe Industry Co., Limited (www.ugsteelmill.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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