Jiangmen Kunxin new Material Technology Co.,Ltd , https://www.jmkunxinplastics.com
1. All levels of hydrostatic pressure test must be carried out after entering the factory.
2. Valves that need to be repaired must be ground.
3. During the overhaul process, it must be carefully checked whether the added packing and the packing gland are tightened.
4. The valve must be checked for dust, sand, iron oxides and other debris inside the valve before installation. If any of the above debris must be cleaned, install it.
5. All valves must be installed with the appropriate level of gasket before installation.
6. The fasteners must be tightened when the flange door is installed, and must be tightened in the symmetrical direction when tightening the flange bolts.
7. During the installation of the valve, all valves must be correctly installed according to the system and pressure. It is strictly prohibited to install and mix the valves. To do this, all valves must be numbered and recorded prior to installation.
Second, on pulverized coal spill prevention measures.
1. All flanges must be installed with sealing material.
2. The areas where powder leakage is likely to occur are coal inlet and outlet coal valves, coal feeders, factory flanges, and all flanged parts. For this purpose, we will carry out a comprehensive inspection of all parts of the plant where the equipment is able to leak powder. We will carry out secondary installations and tighten the fasteners if no sealing material is installed.
3. There is a possibility of powder leakage in the pulverized joints. We will take some measures.
3.1 In the weld before the weld area must be carefully polished metal luster and polished the groove required for welding.
3.2 The gap must be reserved before the counterpart and forcibly prohibited.
3.3 Welding consumables must be used correctly, and must be warmed up as required in cold weather.
Third, on the oil system leakage, running oil and other preventive measures.
1. It is very important to do a good job of leaking, running oil, etc. of the oil system.
2. The system with oil tank must be carefully checked and cleaned before installation.
3. Hydraulic pressure test must be performed on equipment with oil cooler.
4. Hydrostatic test and pickling work should also be done for the oil piping system.
5. During the installation of oil pipelines, all flange joints or unions with threaded fasteners must be equipped with oil-resistant rubber pads or oil-resistant asbestos pads.
6. The leakage point of the oil system is mainly concentrated on the flange and the threaded union. Therefore, the bolt must be tightened evenly when installing the flange. Prevent tight or tight situations.
7. In the process of oil filtration, construction personnel must always adhere to the work position, and it is strictly forbidden to take off posts and string posts.
8. It is necessary to stop the oil filter when changing the filter paper.
9. When installing temporary oil filter connecting pipe (high-strength plastic transparent hose), the connector must be firmly tied with lead wire to prevent the oil filter from running off after running the oil filter for a long time.
10. Relocate the responsible construction personnel to look after the oil filter.
11. Before the start of oil circulation in the auxiliary engine oil system, the Engineering Department will organize a detailed technical disclosure of the personnel responsible for the auxiliary engine oil circulation.
Fourth, prevent equipment, pipe fittings from foaming, dripping, dripping and leaking. The following preventive measures are available:
1.2.5Mpa flange gaskets are made of metal winding pad.
2.1.0Mpa-2.5Mpa flange gasket, asbestos pads, and brush black lead powder.
3.1.0Mpa following water pipeline flange gasket using rubber pads, and brushed black lead powder.
4. The packing of the pump adopts the composite packing of PTFE.
5. For the sealing parts of smoke and wind coal pipes, the used asbestos rope should be twisted once and joined to the joint surface in a smooth manner. It is forbidden to tighten the screws and join it forcefully.
Fifth, eliminate the valve leakage has the following measures:
(For the leak-proof valve, we should do the following measures)
1. Pipeline installation and construction, must establish a good sense of quality, consciously clean iron oxide skin and pipe wall, leaving no debris, to ensure that the pipe wall is clean.
2. First, ensure that the valves entering the site must be 100% hydrostatically tested.
3. Valve grinding should be carried out carefully. All valves (except inlet valves) must be sent to the grinding class for dismantling, inspection and maintenance, and responsibility should be fulfilled. Records and logos should be made consciously to facilitate traceability. Important valves should list the details of the second-level acceptance, so that "seal, printing inspection, recordkeeping" requirements.
4. For the first time, the boilers and drainage doors must be determined in advance. Only the valves are allowed to open during the hydrostatic test. Other valves must not be opened at will, so as to protect the valve core.
5. When the pipeline is flushed, it must be opened large and light to prevent the door core from being damaged.
If you missed, why?
(1) Contact between the opening and closing part and the sealing surface of the valve seat;
(2) Filler and valve stem and stuffing box matching place;
(3) The leakage from the previous position in the connection between the valve body and the valve cap is called endoleak, which is usually referred to as lax, and it will affect the ability of the valve to cut off the medium. The last two leaks are called leaks, that is, the medium leaks from the valve to the outside of the valve. Leakage can cause material loss, pollute the environment and cause accidents when severe.
Falling into practice, analyzing internal leakage, endoleaks are generally:
According to the different diameters of the valve, the pressure difference of the system is different from that of the system medium, and there is an allowable inner leakage standard. In a strict sense, a true '0' leaking valve does not exist. Under normal circumstances, small-diameter cut-off valves are easy to make invisible leaks (not zero leaks), while large-diameter valves are difficult to make invisible leaks. When encountering the phenomenon of internal leakage of the valve, first of all, we should try to understand the specific internal leakage, check the allowable leakage standards of the valve, comprehensive analysis of the system's working environment and other factors when the internal leakage occurs, in order to correctly determine the internal leakage of the valve .
(1) The internal leakage of the parallel gate valve, the working principle of the parallel gate valve is to press the valve side of the outlet side and the sealing surface of the valve seat against the pressure difference of the system. Under the condition that the system pressure is very low, the valve is behind Minor internal leakage may occur. In the event of such endoleaks, it is recommended to continue to observe that the valve's tightness is checked when the system inlet pressure reaches the design pressure or normal working pressure. If there is excessive leakage, the valve should be disassembled and the valve sealing surface should be ground. .
(2) The internal leakage of the wedge gate valve is sometimes due to the different control methods of the valve. Due to the manufacturer's selection during design, the corresponding valve stem and stem nut are strength design methods that do not consider torque control. The way of stroke control, if forcibly changing the stroke control mode of the closed position to torque control, may lead to the damage of the valve stem nut, etc. At the same time, it causes the electric head to malfunction when it is opened, and an open torque fault alarm occurs. When encountering the problem of inner leakage of this type of valve, it is usually possible to manually close it again after the electric switch is closed. It is sufficient to close it. If there is still an inner leakage phenomenon after manual closing, this indicates that there is a problem with the sealing surface of the valve. At this time, disassembling grinding treatment is required.
(3) The inner leakage of the check valve and the sealing of the check valve depend on the pressure difference of the system. When the inlet pressure of the check valve is very low, the outlet pressure will slightly increase. Factors are analyzed to determine the amount of internal leakage. According to the analysis structure, it is decided whether or not to perform overhaul work.
(4) The inner leakage of the large-diameter disc valve, the standard of the inner leakage of the large-diameter disc valve is generally very large. When the inlet pressure increases, the outlet pressure will also increase, and this problem should be judged first. The amount of internal leakage is determined based on the amount of internal leakage.
(5) The inner leakage of the regulating valve, due to the different types of regulating valves, is not the same as the standard for inner leakage. At the same time, the regulating valve generally uses the stroke control method (without the torque control method), so it is generally present within Leakage phenomenon. The inner leakage of the regulating valve should be treated differently. The regulating valve with special inner leakage should be considered when designing and manufacturing. There are many such contradictions in the XX nuclear power plant. Many valves have to be forced into torque control, which is unfavorable to the operation of the regulating valve.
More specific point:
(1) Valve trim material selection and poor heat treatment, hardness is not enough, easily damaged by high-speed fluid.
(2) Due to the limitation of the valve structure, the energy (velocity) of the fluid is not effectively consumed when passing through the valve, and the impact abrasion force on the sealing surface is large; when the velocity is too large, the pressure behind the valve is too small, lower than the saturation pressure, and cavitation occurs. During the cavitation process, all the energy of the bubble collapses at the rupture point and generates several kilonewtons of impact force. The shock wave pressure is as high as 2×103Mpa, which greatly exceeds the fatigue damage limit of the existing metal materials. Very hard discs and seats are also damaged in a very short time and leaks occur.
(3) The valve operates under a small opening for a long time, the flow velocity is too high, the impact force is large, and the valve trim is easily damaged.
First, on the valve leakage, steam leakage prevention measures.