Risk of valve ajar

Harm of 1. valve half open The valve half open is actually the valve is not fully open or closed, partially open the case does not allow all the liquid or gas circulation. An ajar valve can cause the following problems: 1. Water flow is blocked or leaking When the valve is not fully opened, the normal water flow of the pipeline will be blocked or partially leaked, which may cause some water pressure instability and water flow blockage in the pipeline system, which will affect the water pressure and water supply quality, and will also bring water resources. Waste. 2. Reduce the reliability and safety of the pipeline system If the valve is half open, the pipeline system will be in an unstable state, and this unstable state will greatly reduce the reliability and safety of the system. Especially in important situations, this unstable state may cause serious consequences. 2. how to avoid the valve half open The half-open valve is extremely dangerous to the safety of the pipeline system. Therefore, some measures must be taken to avoid this situation: 1. Timely maintenance and inspection of pipeline system The valve half open is often caused by the untimely maintenance of the pipeline system and incomplete detection. Timely maintenance and inspection of the pipeline system can provide a basis for early detection and resolution of problems, thereby avoiding the occurrence of half-open valves. 2. Normal use of the valve Proper use of the valve is the key to preventing a half-open condition. In the valve operation, it is necessary to operate in accordance with the correct procedures and laws, follow the valve switching sequence, and pay attention to the operation essentials. 3. Commissioning before valve installation Before the valve is installed, it needs to be adjusted to ensure that the valve can be fully opened or closed. If it is found that the valve cannot be opened normally, it needs to be adjusted or replaced in time to avoid problems in subsequent use. 4. Strengthen staff training In the enterprise, it is necessary to strengthen the skills training of employees, especially the operators, to ensure that they can operate the valve correctly, and understand the relevant knowledge of the valve, so as to avoid the occurrence of the valve half open.

Why do you want to return a little after the valve is fully opened?

In the process of pipeline use, the role of the valve is to control the flow of fluid. However, before starting to use the valve, the valve needs to be fully opened to ensure smooth fluid flow. However, if the valve is fully opened directly, it is not conducive to the operation and use of the pipeline. Therefore, after the valve is fully opened, it is necessary to return a little, which can protect the valve and the pipeline. Specifically, there are two main reasons for returning a little: 1, to avoid the reverse pressure on the valve sealing surface damage The valve usually uses a sealing surface to control the flow of fluid. When the valve is closed, the sealing surface is used to prevent fluid from passing through the valve. When the valve is fully open, the sealing surface may be subjected to reverse pressure, resulting in damage to the sealing surface. Therefore, it is necessary to return to a point after the valve is fully opened, leaving a gap to reduce the impact of reverse pressure, thereby protecting the sealing surface of the valve. 2. Relieve the impact of pipeline pressure on the valve The fluid in the pipeline will be affected by various pressures during the movement. When the valve is fully open, the fluid pressure in the pipeline will impact the valve, which will adversely affect the valve and the pipeline. Back to a point can alleviate the impact of pipeline pressure on the valve, to protect the safe use of valves and pipelines. 2. back to the specific operation method The specific operation method of returning to a point is as follows: 1. Open the valve fully. 2, slowly close the valve until leaving a small gap. After waiting for a period of time, the valve is completely closed. It should be noted that in the process of returning to a point, it is necessary to operate slowly to ensure that the gap left is appropriate to prevent the normal use of the pipeline from being affected. 3. Summary Valve in the use of the pipeline is a very important part of the valve, the full open and back to a point for the smooth operation of the pipeline and the safe use of valves and pipelines have an important role. When the valve is fully opened, back to the role of a point is to protect the valve sealing surface and ease the impact of pipeline pressure on the valve. When the operation is back to a point, it needs to be carried out slowly and pay attention to leaving appropriate gaps to ensure the safe operation of valves and pipelines.

Valve Maintenance Procedure

1. Cleaning The surface of the valve, the trapezoidal thread on the valve stem and the valve stem nut, the sliding part of the valve stem nut and the bracket, and the gears, worm gears and other components are easy to accumulate a lot of dust, oil and media residues, which will cause wear and corrosion to the valve. Therefore, it is obviously very important to keep the external and active parts of the valve clean and protect the integrity of the valve paint. The dust on the valve is suitable for brush sweeping and compressed air purging. Trapezoidal thread and stolen goods between teeth are suitable for wiping with rag. Oil stains and residues on the valve are suitable for steam purging, even copper wire brushing, until the processed surface and mating surface show metallic luster, and the paint surface shows the natural color of paint. Trap should be responsible for a special person, check at least once per shift, regularly open the flush valve and trap at the bottom of the plug for flushing, or regularly disassemble the flushing, so as to avoid the stolen goods blocking the valve. 2. Lubrication of valve Valve trapezoidal thread, stem nut and bracket sliding parts, bearing parts, gear and worm gear, worm meshing parts and other cooperating parts, all need good lubrication conditions to reduce mutual friction and avoid mutual wear. Some parts are specially equipped with oil cup or nozzle. If it is damaged or lost in operation, it should be repaired and equipped, and the oil circuit should be dredged. Lubrication parts should be regularly refueled according to specific conditions. Often open, high temperature valve is suitable for intervals of a week to a month refueling once; not often open, the temperature is not high valve refueling cycle can be longer. Lubricant organic oil, butter, molybdenum disulfide and graphite. High temperature valve is not suitable for oil, butter, they will be due to high temperature melting and loss, and suitable for injection of molybdenum disulfide and wipe graphite powder. For exposed parts that need lubrication, such as trapezoidal threads, gears and other parts, if grease such as butter is used, it is easy to be contaminated with dust, while molybdenum disulfide and graphite powder are used for lubrication, it is not easy to be contaminated with dust, and the lubrication effect is better than yellow. Graphite powder is not easy to apply directly, a little oil or water can be used to adjust the paste. The plug valve of the oil filling seal should be filled with oil according to the specified time, otherwise it is easy to wear and leak.

How to maintain the valve daily maintenance

1. The valve shall be stored in a dry and ventilated room, and both ends of the passage shall be blocked. 2. Valves stored for a long time should be checked regularly to remove dirt and apply anti-rust oil on the processing surface. 3. After installation, regular inspection should be carried out. The main inspection items are: (1) the sealing surface wear. (2) the valve stem and stem nut trapezoidal thread wear. (3) Whether the packing is outdated and invalid, if damaged, it should be replaced in time. (4) After the valve is overhauled and assembled, the sealing performance test shall be carried out. (I) storage and maintenance The purpose of storage and maintenance is to prevent the valve from being damaged or reduced in quality during storage. In fact, improper storage is one of the important reasons for valve damage. Valves should be kept in good order. Small valves should be placed on shelves. Large valves can be arranged neatly on the warehouse floor. They should not be stacked randomly. Flange connection surfaces should not contact the ground. This is not only for the sake of beauty, but mainly to protect the valve from damage. Due to improper storage and handling, the handwheel is broken, the valve stem is crooked, the fixed nut of the handwheel and the valve stem is loose and lost, etc. These unnecessary losses should be avoided. For valves that are not used temporarily in the short term, asbestos packing should be taken out to avoid electrochemical corrosion and damage to the valve stem. Just into the library of the valve, to check, such as in the transport process into the rain or dirt, to wipe clean, to be stored. The inlet and outlet of the valve should be sealed with wax paper or plastic sheet to prevent dirt from entering. The valve processing surface that can rust in the atmosphere should be coated with anti-rust oil to protect it. Valves placed outdoors must be covered with rain-proof and dust-proof items such as linoleum or tarpaulin. Store the valve warehouse to keep clean and dry. (II) use and maintenance The purpose of use and maintenance is to extend the life of the valve and to ensure reliable opening and closing. Stem thread, often with the stem nut friction, to be coated with a little yellow dry oil, molybdenum disulfide or graphite powder, lubricating effect. Do not often open and close the valve, but also regularly turn the hand wheel, the stem thread to add lubricant to prevent bite. For outdoor valves, the valve stem shall be provided with a protective sleeve to prevent rain, snow, dust and rust. If the valve is mechanical to be moved, add lubricating oil to the gearbox on time.

Treatment Measures of Gate Valve Leakage

When there is leakage or a small amount of leakage inside the gate valve, the first job is to tighten and fix the pressure plate of the valve body, and to strengthen the preload between the pressure plate and the wedge-shaped sealing ring by improving the bolts, which can help the plastic deformation of the sealing ring, thus reducing the gap size between the valve body, the pressure plate and the sealing ring, and avoiding the leakage phenomenon of the valve self-sealing. If the amount of leakage does not change significantly when tightening and fixing the bolts, the tightening measures should be stopped immediately and other treatment measures should be taken instead. Injection of sealant through grease injection hole When there is a small internal leakage of the valve, the sealing surface or packing can be injected with grease through the grease injection hole to temporarily alleviate the internal leakage of the valve. When it is convenient for maintenance, the valve can be disassembled and returned to the factory for maintenance. Welding and strengthening the gap between the end face of the valve body, the stuffing box and the pressure plate To deal with the self-sealing leakage of the valve, it is necessary to do a good job of disassembling the valve handwheel and the valve frame. First, it is necessary to cooperate with the technicians to grasp and adjust the working conditions on the site. Then, after all the valves are opened, the bolts fixed on the valve frame are removed. After the rotary valve frame makes it clear that the valve stem does not rise or fall, the valve frame is removed. After removing the valve frame, the valve body shall be exposed at the pressure plate of the valve, and the gap between the pressure plate and the valve body shall be sealed and welded. In order to consider the reassembly process of the valve frame after blocking the leakage position, the welding gap size shall be between 5mm and 8mm, while the welding angle and the position of the pressure plate shall be 45 degree angle, and shall be polished according to the actual assembly situation. Check actuator zero position The zero position of the actuator is not set accurately, and the valve is not fully closed. Manually fully open and fully close the valve, and then adjust the zero position of the actuator to ensure that the actuator can accurately fully open or fully close the valve. Valve body repair welding or return to factory for repair When there is leakage of the valve body, the valve manufacturer can repair the defects of the valve body, or return to the factory for repair and replacement of the valve body. First of all, the defects of the valve body should be judged. Penetrating cracks, penetrating defects and shrinkage porosity exceeding a certain area are not allowed to be repaired. In this case, the valve body can only be replaced at the factory. For the valve body defects that can be repaired, the appropriate welding process should be formulated, the welding method, electrode material, post-weld stress relief method should be determined, and the welding position should be properly tested to ensure that the repair meets the requirements.

Causes of valve sealing surface lax and treatment method of sealing surface leakage

1. The sealing surface that is not normally open or closed is easy to contact with foreign objects when allowed. Often close or open the valve chamber, leaving a small seam, repeat several times, and flush out the foreign objects on the sealing surface. 2. Equipment and pipe corrosion, welding ballast, bolts and other items stuck on the sealing surface of the valve should be set up sewage, filtration and other protection devices, regular inspection of the protection device and valve bottom plug, remove foreign matter. 3. The medium itself has hard particles embedded in the sealing surface. Generally, gate valves should not be selected. Ball valves, plug valves and soft sealing surfaces should be selected. 4. The sealing surface is uneven or the angle is not straight, not round, can not form a closed line sealing surface processing and grinding method should be correct, before assembly should be colored inspection, printing shadow circle and continuous 5. Improper selection of sealing surface material or valve selection without working conditions, corrosion, erosion wear and other phenomena, strictly in accordance with the working conditions to select the valve or replace the sealing surface. For batch products, the corrosion resistance, wear resistance, wear resistance and other properties of the sealing surface should be tested 6. Sealing surface surfacing and heat treatment are not operated as specified. They wear due to low hardness, corrosion due to the burning of alloying elements, and cracking due to excessive internal stress. Surfacing and heat treatment shall comply with regulations and specifications, and strict quality inspection system shall be adopted 7. The sealing surface hardening, ammonia penetration, boronizing, chromium plating and other processes of sealing surface peeling or loss of original performance due to excessive grinding shall be carried out in strict accordance with the rules and specifications of this technical requirement. When repairing, the cutting amount of the penetration layer of the sealing surface should not exceed 1/3. 8. If the shut-off valve is used as a throttle valve and a pressure reducing valve, and the sealing surface is corroded to cut off the valve, it is not allowed to be used as a throttle valve and a pressure reducing valve, and the closing parts should be in a fully open or fully closed position. If the medium flow and pressure need to be adjusted, throttle valve and pressure reducing valve should be set respectively 9. Close the parts to the fully closed position, continue to apply too much closure, the sealing surface is crushed, the squeeze deformation closing force should be moderate, after the valve is closed, immediately stop closing the valve, correct the "valve closed more strictly, the better" error method of operation.

How to deal with valve leakage, steam leakage prevention measures

As the control unit in the fluid conveying system, the valve has the functions of cut-off date, regulation, guidance, prevention of countercurrent, pressure regulation, diversion or overflow and pressure relief. It is indispensable for many industrial control components. Once the valve fails, especially The leakage incident not only affects the stable operation of industrial and mining equipment, but also may be harmful to the environment and cause incalculable economic and social losses to the society. We must learn to identify and prevent common leakage failures of valves. Generally speaking, common leakage failures of valves include two types, namely stuffing box leakage and closed leakage. The leakage of stuffing box is the main aspect of operation, bubbling and dripping, which is common in factories. To understand how to deal with valve leakage, steam leakage, we must first understand why there is leakage, steam leakage, is the so-called retreat. The valve must have a good seal to maintain air tightness. If there is a problem with the seal, a leak will occur.

Causes of valve sealing surface damage

Because the seal plays a role in cutting off and connecting, adjusting and distributing, separating and mixing the medium in the flow channel of the valve, the sealing surface is often corroded, eroded, worn and easily damaged by the medium. Sealing surface damage is caused by man-made damage and natural damage. Man-made damage is caused by improper design, poor manufacturing, improper material selection, improper installation, improper use, poor maintenance and other factors. Natural damage refers to the wear of the valve under normal working conditions, as well as the inevitable corrosion and erosion of the sealing surface caused by the medium. The reasons for the damage of the sealing surface are summarized as follows: The poor processing quality of the sealing surface is mainly manifested in defects such as cracks, pores and fixture design of the sealing surface. The hardness of the sealing surface is too high or too low due to improper selection and specification of surfacing and heat treatment during surfacing and heat treatment operations. The hardness of the sealing surface is uneven and corrosion resistant due to material errors or heat treatment failure. The main reason is that the bottom metal is blown to the top during surfacing, diluting the alloy composition of the sealing surface. Of course, there are also design issues. Damage caused by improper selection and improper operation. The main performance is not selected according to the working conditions of the valve, the throttle valve using cut-off valve, resulting in the closing pressure is too large, close too fast or too loose, so that the sealing surface is eroded and worn. Improper installation and improper maintenance can cause abnormal operation of the sealing surface, abnormal valve operation, and premature damage to the sealing surface. Chemical corrosion of the medium, the medium in the case of no current around the sealing surface, the medium directly and the sealing surface of the chemical interaction, corrosion of the sealing surface. Electrochemical corrosion, sealing surface contact, sealing surface contact with the closed body and valve body, as well as medium concentration difference, oxygen concentration difference and other reasons, will produce potential difference, electrochemical corrosion, resulting in the anode side of the sealing surface is corroded. Media erosion is the result of wear, erosion and cavitation of the sealing surface when the medium flows. Medium at a certain speed, the medium of the plankton particles impact the sealing surface, causing local damage, high-speed flow of the medium directly scour the sealing surface, causing local damage, medium mixed flow and local vaporization, bubble explosion impact sealing surface, causing local damage. The alternating action of dielectric erosion and chemical corrosion will strongly corrode the sealing surface. When mechanically damaged, the sealing surface will cause scratches, scratches, extrusion and other damage to the za when it is opened and closed. Between the two sealing surfaces, under the action of high temperature and high pressure, atoms penetrate each other, resulting in adhesion. When the two sealing surfaces move relative to each other, the adhesive force tends to tear. The higher the surface roughness of the sealing surface, the greater the possibility of this phenomenon. In the process of closing the valve, the valve in the process of returning to the valve seat will encounter and squeeze the sealing surface, so that the sealing surface of local wear or depression. Fatigue damage, the sealing surface in long-term use, the three fine valves under the action of alternating load lead to sealing surface fatigue, cracks and peeling layer. After long-term use, rubber and plastics are prone to aging, resulting in poor performance. From the above analysis of the causes of damage to the sealing surface, it can be seen that in order to improve the quality and service life of the valve sealing surface, it is necessary to select the appropriate sealing surface material and reasonable sealing structure and processing methods.