Valve common sense: valve seal and performance typical valve gate valve: wedge gate valve and parallel gate valve

Valve common sense: valve seal and performance typical valve gate valve: wedge gate valve and parallel gate valve

Valve common sense: valve seal and performance
(I) Valve seal and performance
1, the valve in the final assembly must be carried out after the performance test, to check whether the product meets the design requirements and whether to meet the national quality standards. Defects in valve materials, blanks, heat treatment, machining and assembly can generally be exposed during testing. Conventional tests include shell strength test, sealing test, low pressure sealing test, action test, etc., and according to the need, the next test will be carried out after passing the test successively.
2, strength test: the valve can be regarded as a pressure vessel, so it needs to meet the requirements of bearing medium pressure without leakage, so the valve body, valve cover and other parts of the blank should not exist affect the strength of cracks, loose pores, slag and other defects. In addition to the strict inspection of the appearance and internal quality of the blank, the valve manufacturer should also carry out the strength test one by one to ensure the performance of the valve.
3, the cause of the leakage of the pressure reducing valve
As an important component of the hydraulic system, the main function of the pressure reducing valve is to make the outlet pressure of the system always lower than the level of the inlet pressure, to maintain the stability of the outlet pressure of the system, and the outlet pressure of the system is not affected by the inlet pressure and flow fluctuations; However, once the sealing surface of the pressure reducing valve leaks, it not only affects the normal production, but also causes the loss of hydraulic oil and pollution of the environment; In the Marine hydraulic system, the pressure reducing valve as the main control element, its sealing importance is not to be underestimated. After joint research and analysis with relevant experts found that the sealing between the connecting sleeve of the pressure reducing valve and the valve body is mainly dependent on the O-ring between the connecting sleeve and the inner wall of the valve body for circumferential sealing, the sealing once effective, its external leakage is inevitable.
4, butterfly valve test and installation and troubleshooting methods
Butterfly valve whether manual, pneumatic, hydraulic, electric parts are strict debugging before they go out, the user when the re-inspection sealing performance, on both sides of the import and export shall be uniformly fixed, close the disc valve, pressure on suction side, in the export side to observe whether leak phenomenon, before the trial, the strength in the pipeline should open the disc plate, to prevent damage to the seal.
Although the products are strictly inspected and tested before leaving the factory, there are some automatic screw displacement of some products during transportation, which needs readjustment, pneumatic, hydraulic, etc., please read the operating instructions of the supporting driving device.
When the electric drive disc valve leaves the factory, the opening and closing stroke of the control mechanism has been adjusted. In order to prevent the direction of the power switch is wrong, the user in the first time after switching on the power, first open manual to half open position, in accordance with the electric switch to check the direction of the indicator plate and the valve closed direction can be consistent.
5, pneumatic control valve/pneumatic cut-off valve is compressed air as power source, the cylinder as actuator, and by means of electric valve positioner, converters, solenoid valve, a valve to drive the valve such as attachment, realize the switch quantity or proportion type adjustment, industrial automation control system receives the control signal to complete regulating the flow of pipeline medium, pressure, temperature and other process parameters. Pneumatic control valve is characterized by simple control, rapid response, and intrinsically safe, do not need to take explosion-proof measures again.
6, stainless steel butterfly valve in the process of use rust phenomenon. Through metallographic structure analysis, staining test face, heat treatment test face, SEM and other tests, it is found that the key factor of material corrosion is because the carbide precipitates along grain boundaries in the material to form a chrome-poor area, resulting in corrosion of stainless steel butterfly valve. The stainless steel butterfly valve made of CF8M is corroded during use. After normal heat treatment, the structure of austenitic stainless steel should be austenitic at room temperature, and the corrosion resistance is good. In order to analyze the reason of corrosion of butterfly valve, samples were taken from it for analysis.
(ii) Flange seal and leakage seal treatment methods
There are many factors affecting flange sealing. The main ones are: bolt preload; Sealing surface type; Gasket performance; Flange stiffness; Operating conditions. ANSI flanges have been designed by the American National Standards Institute to provide the oil and gas industry with a suitable and effective sealing technology for decades. However, as the needs of the oil and gas industry have changed, ANSI flange deficiencies have been exposed. The principle of cost-effectiveness, environmental protection, and human health and safety guarantees are what operators and contractors face in the 21st century
Conclusion:
The new design and installation of the control system, in order to ensure that the regulator can work normally when driving, and make the system safe operation, the new valve before installation, should first check the valve nameplate mark is consistent with the design requirements. The following projects should also be debugged. Basic error limit; Full stroke deviation; Back to the poor; Dead zone; Leakage (in the case of strict requirements). If it is the original system of the regulating valve has been overhauled, in addition to the above check, but also should be the old valve stuffing box and joint parts of the sealing check.
Typical valve gate valve: wedge gate valve and parallel gate valve gate valve is used as a cut-off medium, in full open when the whole flow straight through, the medium running pressure loss is ** * small. Gate valves are usually suitable for operating conditions that do not require frequent opening and closing, and keep the gate fully open or fully closed. Not intended for use as a regulator or throttling.
The gate valve is used as a cut-off medium, the whole flow is straight through when it is fully open, and the pressure loss of the medium running is ** * small. Gate valves are usually suitable for operating conditions that do not require frequent opening and closing, and keep the gate fully open or fully closed. Not intended for use as a regulator or throttling. For THE HIGH speed flow MEDIUM, THE gate CAN cause the gate vibration in the condition of local opening, and the vibration may damage the sealing surface of the gate and seat, and the throttle will cause the gate to suffer from the erosion of the medium.
From the structural form, the main difference is the form of the sealing element used. According to the form of sealing elements, gate valves are often divided into several different types, such as wedge gate valves, parallel gate valves, parallel double gate valves, wedge double gate gates, etc. ** Commonly used forms are wedge gate valves and parallel gate valves.