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Valve sealing pair
The valve sealing pair is the part that closes when the valve seat and the closing member are in contact with each other. During use, the metal sealing surface is easily damaged by the entrapped medium, medium corrosion, wear particles, cavitation and erosion. Such as wear particles. If the wear particles are less uneven than the surface, the surface accuracy of the sealing surface will be improved when the sealing surface is running in, and will not deteriorate. On the contrary, the surface accuracy will deteriorate. Therefore, when selecting wear particles, factors such as their materials, working conditions, lubricity and corrosion to the sealing surface must be considered comprehensively.
Like wear particles, when we choose seals, we must comprehensively consider various factors that affect their performance to prevent leakage. Therefore, we must choose those materials that are resistant to corrosion, abrasion and erosion. Otherwise, the lack of any requirement will greatly reduce its sealing performance.
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The sealing principle of the leakage channel
The valve seal is composed of the roughness of the unevenness scattered on the wave surface and the waviness of the distance between the wave crests. In the case that most of the metal materials in our country have low elastic strain, if the sealing state is to be achieved, the compression force of the metal material needs to be higher, that is, the compression force of the material must exceed its elasticity. Therefore, when designing the valve, the sealing pair is matched with a certain hardness difference, and under the action of pressure, a certain degree of plastic deformation sealing effect will be produced. Airtech Valve
If the sealing surface is made of metal materials, then the uneven protruding points will appear first, and only a small load can be used to plastically deform these uneven protruding points. When the contact surface increases, the unevenness of the surface becomes plastic-elastic deformation. At this time, the roughness on both sides of the recess will exist. When a load that can cause serious plastic deformation of the underlying material is applied, and the two surfaces are in close contact, the remaining diameters can be tightly closed along the continuous line and the circumferential direction.
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Valve gas tightness
According to Poisson's formula, the airtightness of a gas is related to the gas molecules and the viscosity of the gas. Leakage is inversely proportional to the length of the capillary tube and the viscosity of the gas, and proportional to the diameter of the capillary tube and the driving force. When the diameter of the capillary is the same as the average degree of freedom of the gas molecules, the gas molecules will flow into the capillary with free thermal motion. Therefore, when we are doing the valve sealing test, the medium must be water to play a sealing role, and air or gas cannot play a sealing role. Airtech Valve
Even if we reduce the diameter of the capillary tube below the gas molecule through plastic deformation, it still cannot stop the flow of gas. The reason is that the gas can still diffuse through the metal wall. Therefore, when we do the gas test, we must be stricter than the liquid test.
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Valve sealing principle two
Dynamic seal
Dynamic sealing refers to the sealing that prevents the medium flow in the valve from leaking with the movement of the valve stem. This is a sealing problem during relative movement. The sealing method is mainly to use a stuffing box. There are two basic forms of stuffing box, namely gland type and compression nut type. Gland type is currently the most used form. Generally speaking, it can be divided into combined type and integral type. Although each type is different, it basically contains bolts for pressing. Compression nut type is generally used for smaller valves. Due to the smaller size of this type, the compression force is limited. Airtech Valve
In the stuffing box, since the packing is in direct contact with the valve stem, all requirements for packing have good sealing performance, low friction coefficient, ability to adapt to the pressure and temperature of the medium, and corrosion resistance. At present, the more commonly used fillers include rubber O-rings, PTFE braided packing, asbestos packing and plastic molding packing. Each kind of packing has its suitable conditions and scope, and it is selected according to specific needs.
Sealing is to prevent leakage, so the principle of valve sealing is also studied from leakage prevention. There are two main factors that cause leakage. One is the most important factor affecting the sealing performance, that is, there is a gap between the seal pairs, and the other is the pressure difference between the two sides of the seal pair. The principle of valve tightness is also analyzed from four aspects: liquid tightness, gas tightness, leakage channel sealing principle and valve sealing pair.
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Valve sealing principle one
Static sealing
Static sealing refers to the formation of a seal between two static sections. The sealing method is mainly to use gaskets. There are many types of gaskets. Frequently used gaskets include flat gaskets, O-rings, wrap gaskets, special-shaped gaskets, wave gaskets and winding gaskets. Each type can be further divided according to the different materials used.
Airtech Valve
① Flat washer. Flat washers are flat washers that are placed between two static sections. Generally, they can be divided into plastic flat washers, rubber flat washers, metal flat washers and composite flat washers according to the materials used. Each material has its own flat washers. The scope of application.
②O-ring. O-ring refers to a gasket with an O-shaped cross-section. Because its cross-section is O-shaped, it has a certain self-tightening effect, so the sealing effect is better than that of a flat gasket.
③Pack the gasket. Wrapped gasket refers to a gasket that wraps a certain material on another material. Such gaskets generally have good elasticity and can enhance the sealing effect.
④ Special-shaped washer. Special-shaped washers are those with irregular shapes, including oval washers, diamond washers, gear washers, dovetail washers, etc. These washers generally have a self-tightening effect and are mostly used in high and medium pressure valves.
⑤ Wave washers. Wave washers are washers with only wave shapes. Such washers are usually composed of a combination of metal and non-metal materials, and generally have the characteristics of small pressing force and good sealing effect.
⑥ Wrap the gasket. Spiral wound gasket refers to a gasket formed by tightly adhering a thin metal belt and a non-metallic belt together and winding them. This type of gasket has good elasticity and tightness.
The materials for gaskets mainly include three major categories, namely, metallic materials, non-metallic materials and composite materials. Generally speaking, metal materials have high strength and high temperature resistance. Commonly used metal materials are copper, aluminum, steel, etc. There are many types of non-metallic materials, including plastic products, rubber products, asbestos products, hemp products, etc. These non-metallic materials are widely used and selected according to specific needs. There are also many types of composite materials, including laminates, composite panels, etc., which are also selected according to specific needs. Generally, wave washers and winding washers are used more.
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Valve seat and valve plate leakage
Leakage at the valve seat and valve plate is the most common phenomenon in the installation or maintenance of gate valves. Generally, there are two types: one is the leakage of the sealing surface, and the other is the leakage of the root of the sealing ring.
First, the accuracy of the sealing surface contacting the valve seat and the valve plate should be checked. The sealing surface must be at least ground. If the surface accuracy is found to be too rough, it should be removed and reground. Secondly, check the sealing surface for defects such as pitting corrosion, indentation, sand holes, cracks, etc. If this happens, the valve plate or valve seat must be replaced. For valve seats with compression springs, the elasticity of the compression springs should be checked to meet the requirements. If the elasticity is weakened, the compression springs should be updated. Furthermore, check whether the T-shaped connection between the valve plate and the valve stem is too loose, causing the valve plate to be inclined during the compression process. In this case, the valve plate must be removed and adjusted to the best size.
The internal opening of the valve body is easy to enter foreign objects such as welding, iron filings, and impurities during the installation process. Such debris should be cleaned up before installation. If you forget to clean or do not clean it thoroughly, it will cause the valve plate to close less than the expected depth and cause leakage. In this case, you need to remove the valve body and clean it again.
When installing the valve seat, you should use a special installation tool to check whether the valve seat is installed in place. If the thread is not screwed to the expected depth, there will be leakage at the valve seat. In this case, use a special tool to reinstall the valve. For installation.
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Valve cover leakage
The valve cover leaks. This fault phenomenon is mainly manifested in the leakage of the packing seal. First, check whether the seal is selected correctly and whether it is compatible with the sealing groove. If there is such a problem, replace the sealing ring or repair the sealing groove. Secondly, check the seals for burrs, fracturing, twisting and other phenomena. In this case, replace the seals. Again, check whether the sealing surface of each seal groove is rough or has other defects. If there is a defect, remove the defect or replace the damaged part.
There are packings in the bonnet or bracket that are sealed by compression. The installation of these packings should be checked. If the upper and lower packings are found to be reversed, they must be removed and reinstalled in accordance with the correct method. Pay particular attention to the joint surface of the packing seal Of cooperation. Furthermore, check whether the accuracy of each contact surface of the seal meets the specified requirements.
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Gate valve and gate valve junction leakage
First of all, check whether the connecting bolts of the gate valve and the gate valve are tightened. If the bolts are not tightened, the gasket ring and the flange sealing groove surface are not fully combined, which often leads to leakage. The bolts and nuts should be inspected in order, and all bolts should be tightened until the gasket ring is compressed. Secondly, the size and accuracy of the seal ring and flange sealing groove surface should be checked. If the size of the seal contact surface is incorrect or too rough, the seal ring should be repaired or updated. In addition, check whether there is some corrosion, sand holes, sand holes or impurities in the contact surface of the gasket ring and the flange sealing groove. If such defects exist, they must be repaired, repaired or cleaned accordingly.
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Valve tightness inspection
When testing the high-pressure valve system with an ultrasonic detector, a comparative reading is usually used to determine whether there is a leak: the first step is to contact the upstream side to reduce the sensitivity and minimize other sounds; the second step is to contact the valve seat and the downstream side; the third Step by step, compare the difference in sound. If the valve leaks, the vibration intensity of the valve seat or the downstream side is equal to or greater than that of the upstream side.
When detecting a low-noise system, contact the downstream of the valve, use the frequency selection method to clearly hear the sound of the liquid flow, and determine whether it is leaking and the leakage status according to the reading size.
When using the four-point comparison method to detect downstream interference, these interferences are sometimes very large and can be propagated to the area that needs to be detected, resulting in a false indication of valve leakage. The four-point method includes: selecting two upstream equidistant points A and B, and then selecting two downstream equidistant points C and D. Compare the signal strengths at points A and B with the signal strengths at points C and D. If point C is higher than points A and B, the valve is leaking; if point D is higher than point C, the sound is from the downstream From other points.
When gas and liquid leak in the pipeline, ultrasonic waves are generated due to friction. SONAPHONEE can receive ultrasonic signals and convert the ultrasonic signals into electrical signals and display them on the display. At the same time, the acoustic emission signal is processed into audible sound and transmitted to the headset, and can be transmitted to the PC through the infrared interface.
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The characteristics of the acoustic emission signal when the valve leaks
When the tightness of the valve is poor, a small amount of fluid is always ejected through the gap of the valve to produce a high-speed jet. This high-speed fluid impacts the pipe wall to excite elastic waves, that is, acoustic emission. It belongs to a continuous acoustic emission signal, similar to white noise, and its frequency is between 30 and 50 kHz.
The characteristics of the acoustic emission signal generated when the valve leaks: 1 the acoustic emission wave excited by the leakage is continuous; 2 the acoustic emission signal generated by the leakage is relatively strong, and its amplitude is proportional to the leakage rate and the root mean square of the signal The value is proportional.
According to the characteristics of the acoustic emission signal generated by the leak, the characterization parameters adopt acoustic emission rate and energy, which can obtain more abundant acoustic emission signal data and provide a more sufficient basis for fault identification.
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Air pressure reducer installation and maintenance method Air pressure reducer installation and maintenance method
medical oxygen regulator The air pressure reducer is one of the auxiliary units of the pneumatic unit combination meter. It will adjust the air source from the air compressor to the required pressure value to stabilize the pressure, and provide air source for various pneumatic instruments and other pneumatic equipment. The air pressure reducer adjusts the pressure of the air source from the air compressor and adjusts it to the required pressure value to stabilize the pressure. It is used as an auxiliary device to supply various types of pneumatic instrument air sources or an accessory device for other pneumatic equipment.
Air pressure reducer installation, use and maintenance:
1. The meter must be connected to the pipeline in the direction of the arrow or according to the "input" and "output" without error. The installation is shown in the table and the installation size (installation screw hole, center distance mm).
2. There is an adjusting screw at the bottom of the instrument cover for water discharge and sewage discharge.
3. The instrument does not need special maintenance under normal normal use conditions. It is recommended to overhaul it after six months of use. When the filter element is blocked, it can be boiled with 10% dilute hydrochloric acid for half an hour. After drying, it can be restored by blowing back air. characteristic.
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The core advantages and product features of large-diameter stainless steel pressure reducing valves.
The core advantages and product features of large-diameter stainless steel pressure reducing valves
The large-diameter stainless steel pressure reducing valve is a throttling element whose local resistance can be changed, that is, by changing the throttling area, the flow velocity and the kinetic energy of the fluid are changed, resulting in different pressure losses, so as to achieve the purpose of decompression. Then rely on the adjustment of the control and adjustment system to balance the fluctuation of the pressure behind the valve with the spring force, so that the pressure behind the valve remains constant within a certain error range.
The large-diameter stainless steel pressure reducing valve is a combination of new technology, practical materials and some innovations. It is tested, developed and designed on the basis of design features. It has a longer service life and is more reliable. The design of self-lubricating bushing ensures product The safe operating life is extended; the spherical design is used to completely avoid the collision and deformation of the limit bolt.
Large-diameter stainless steel pressure reducing valve belongs to pilot piston type pressure reducing valve: it is mainly used for gas pipeline, such as gas can be divided into air pressure reducing valve, nitrogen pressure reducing valve, oxygen, hydrogen, liquefied gas pressure reducing valve, natural gas pressure reducing valve Wait. It belongs to pilot piston type pressure reducing valve. The large-diameter stainless steel pressure reducing valve is composed of a main valve and a pilot valve. The main valve is mainly composed of valve seat, main valve disc, piston, spring and other parts. The pilot valve is mainly composed of valve seat, disc, diaphragm, spring, adjustment spring and other parts. The outlet pressure is set by adjusting the adjustment spring pressure, the outlet pressure change is sensed by the diaphragm, and the main valve is adjusted by the piston opening and closing to drive the main valve The size of the overflow area at the throttling part realizes the function of decompression and voltage stabilization.
Set the outlet pressure by adjusting the spring pressure, and use the diaphragm to sense the outlet pressure change. The pressure adjustment range is mainly related to the rigidity of the pressure adjustment spring. The smaller the output pressure fluctuation, the better the characteristics of the large-diameter stainless steel pressure reducing valve. The output pressure must be Below the input pressure-the fixed value basically does not change with the change of the input pressure.
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How to use CO2 pressure reducer safely?
medical vacuum regulator The carbon dioxide pressure reducer is a special device that automatically reduces the working pressure of the pipeline. The opening of the opening and closing parts in the valve body is used to adjust the flow of the medium to reduce the pressure of the medium. At the same time, the opening and closing is adjusted by the effect of the pressure behind the valve The opening of the piece keeps the pressure behind the valve within a certain range, and keeps the outlet pressure within a certain range when the inlet pressure changes continuously.
The characteristic of the pressure reducer is a device that adjusts the variable inlet pressure to the most stable outlet pressure and flow rate. Under the change of input pressure, the flow rate can still be arbitrarily adjusted within the specified range and maintain its set flow value. The electric heating device adopts an electric heating system with automatic temperature control, which can prevent freezing and reduce the output flow. It is mainly used in the beverage industry, gas shielded welding, agricultural cultivation and cultivation, chemical industry and hospitals.
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stainless steel pressure reducing
Safe use of pressure reducing valve
1. To fix the gas cylinder on the wall, pillar or special cart, make sure that the gas cylinder does not fall on the ground.
2. Before use, confirm that the pressure reducer is intact and check for grease contamination. If there is grease, it should be cleaned by professionals. The impurities, dirt and dust on the pressure reducer should be removed.
3. Check whether the cylinder valve is contaminated with grease, whether the thread is damaged, and whether there are impurities or dirt. If grease or thread damage is found, the cylinder should not be used and the gas supply unit should be notified of these conditions. Remove impurities, dirt and dust from the cylinder valve.
4. Install the pressure reducer to the gas cylinder, and tighten all the connecting joints tightly.
5. Before opening the cylinder valve, turn the regulator screw counterclockwise until the adjustment spring is not compressed.
6. Do not stand on the front or back of the pressure reducer when opening the cylinder valve. The cylinder valve should be opened slowly until the high pressure indicates the cylinder pressure reading.
7. Rotate the pressure reducer to adjust the screw clockwise to express the low pressure to the required working pressure. If it is too high, loosen the adjusting screw, and readjust after releasing a part of the air.
8. To check for air leaks, first close the cylinder valve, and then turn the adjusting screw counterclockwise one turn. If the reading of the high-pressure meter decreases, then the high-pressure part of the pressure reducer or the cylinder valve is leaking. If the reading of the low-pressure meter decreases, the low-pressure part of the pressure reducer or the pipeline and equipment behind the pressure reducer are leaking. If the high-pressure meter reading decreases and the low-pressure meter reading increases at the same time, it means that there is a leak at the valve seat of the pressure reducer. All of the above gas leaks can be tested with good and safe solutions.
10. When the gas cylinder is not in use, close the gas valve. When the work is completed, first close the gas cylinder valve, then open the valve on the welding, cutting tool or equipment to exhaust all the gas from the pressure reducer. Then close the valve just opened, and then adjust the screw counterclockwise until the adjustment spring is not compressed.
11. When using the pressure reducer, strictly implement the "Cylinder Safety Supervision Regulations" issued by the State Administration of Labor.
12. If the pressure reducer and the supporting pressure gauge are damaged or abnormal, they should be repaired immediately.
13. The repair of the pressure reducer must be carried out by professionals.
14. The other parts to be replaced during repair should be the same parts of the same model of our factory, otherwise it may cause problems or fail to meet the performance requirements of the product.
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Characteristics and working principle of large-diameter stainless steel pressure reducing valve
The large-diameter stainless steel pressure reducing valve is mainly used in various building water supply systems, fire fighting systems, central air conditioning systems, heating systems, etc. It is used for branch pipe decompression, which can be adjusted to make the pressure distribution more balanced and optimize the water supply efficiency of high-rise buildings. Its installation can replace the pressure partition or frequency modulation and variable speed water supply, which can reduce the pressure load of water appliances in the low zone and save water, and effectively reduce the failure of the valve due to debris.
1. Features
Accurately control the dynamic and static pressure without fluctuation due to the change of upstream pressure.
Double-piston large flow rate (about 3 times that of common valves) and low flow noise.
The internal structure is compact and reasonable, saving a lot of installation space consumption.
The installation environment requirements are simple, the pressure adjustment is wide, and the water supply pressure can be adjusted on site without professional operation.
Select stainless steel material, high strength and environmental protection.
Second, working principle
The valve is mainly composed of the valve seat, the main valve disc, the piston, the upper and lower piston mechanisms, the spring and other parts. By adjusting the pressure of the spring, it directly acts on the two pistons of the main and auxiliary pistons to drive the valve disc down and away from the valve body. In the passage, the outlet pressure acts on the bottom surface of the two pistons to form a buoyancy force to drive the valve disc to rise and coincide with the valve seat to close the water flow. When the buoyancy force exceeds the spring setting value (equivalent to the water pressure value), the spring is compressed, the valve flap closes, and the outlet The pressure will basically remain at the set value (the change is only 8% of the change in the inlet pressure); when the downstream water is used, the outlet pressure drops, the disc spring is pushed away from the valve seat by the compression spring tension, and the large-diameter stainless steel is opened to reduce pressure Valves are automatically replenished according to consumption.
Three, matters needing attention:
1. For the convenience of operation and maintenance, the valve is generally installed upright on a horizontal pipeline.
2. When installing, pay attention to make the flow direction of the medium in the pipeline coincide with the direction of the arrow shown on the valve.
3. In order to prevent the valve debris from being blocked, a filter should be installed at the front of the valve.
4. The use occasions of uninterruptible supply should have bypass valve or adopt two-way mode, one for one use and one for standby.
5. For the first water flow, please pay attention to empty the pipeline air to avoid false high pressure to protect the pressure gauge and obtain the correct pressure.
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Gas cylinder oxygen regulator
I. Overview:
The gas cylinder oxygen regulator is generally a decompression device for bottled gas. When the inlet pressure and outlet flow rate change, ensure that the outlet pressure is always stable. An increase in the low-pressure meter reading may indicate potential danger and hidden danger.
2. Features
1. Adopt plexiglass dial, the numbers are clearly visible, strong and durable;
2. Brass forged valve body, compact structure, good pressure resistance, durability, anti-leakage;
3. Scientific design, high sensitivity, profound interpretation of dial, low-pressure meter configuration is 0-2.5MPa
4. Professional welding seam smoothing rules by skilled welders
3. Details
1. All-copper material: All-copper material prevents leakage. The entire pressure reducing valve is made of copper except for the pressure gauge;
2. Built-in safety valve: when the output pressure is greater than 1.3 times of the rated pressure, the pressure reducing valve automatically opens the valve to relieve the pressure and reduce the pressure;
3. Low-pressure meter: The dial is covered with a scratch plastic protective film, the dial diameter is 60mm, and the standard output pressure is 0-1.6MPa;
4. High-pressure meter: The dial diameter of the high-pressure meter is 60mm, the standard rated output pressure is 0-1.5MPa, and the dial is covered with a scratch plastic protective film
Fourth, the maintenance and maintenance of the gas cylinder oxygen regulator
1. When using a pressure reducer, a shut-off valve must be installed in the high-pressure input pipeline. It is recommended to install a safety valve in the pipeline that outputs low pressure, because the safety device on the pressure reducer has a small abandonment hole and cannot replace the safety valve to exhaust a lot.
2. When linking to the pipeline, be sure to recognize the direction of the entrance and exit arrows, and do not connect them in the wrong way.
3. Link money must carefully clean the inlet and outlet of the pressure reducer, and the gas pipeline must be cleaned.
4. After installing the pressure reducer on the link, first fully relax the adjusting spring, slowly open the shut-off valve of the pressure reducer, and check whether the air tightness of each link and the pressure of the low-pressure chamber increase. When it is completely airtight and the pressure in the low-pressure chamber is still zero, you can start to slowly adjust the pressure reducer to the required decompression pressure
5. When it is found that the pressure reducer is damaged or leaks, it should be repaired immediately.
6. The pressure reducer should be properly stored before and after use to avoid impact and vibration.
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High pressure oxygen pipeline pressure reducing valve
High-pressure oxygen pipeline pressure reducing valves often use oxygen, nitrogen, hydrogen, argon and other gases in physical chemistry experiments. These gases are generally stored in special high-pressure gas cylinders. When in use, the gas pressure is reduced to the range required by the experiment through the pressure reducing valve, and then fine-tuned by other control valves, so that the gas is input to the system. The commonly used pressure reducing valve is an oxygen pressure reducing valve, abbreviated as oxygen meter.
working principle
The high-pressure chamber of the high-pressure oxygen pipeline pressure reducing valve is connected to the steel cylinder. The low-pressure chamber is the gas outlet and leads to the use system. The indicated value of the high pressure meter is the pressure of the gas stored in the cylinder. The outlet pressure of the low pressure gauge can be controlled by the adjusting screw. When in use, first open the cylinder master switch, and then turn the low-pressure gauge pressure adjustment screw clockwise to compress the main spring and drive the membrane, spring pad and ejector rod to open the valve. In this way, the imported high-pressure gas enters the low-pressure chamber after being throttled and decompressed from the high-pressure chamber, and then leads to the working system through the outlet. Turn the adjusting screw to change the opening height of the valve to adjust the throughput of high-pressure gas and achieve the required pressure value.
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