The high temperature valve has good hardenability and can be deeply quenched instead of the surface quenching of the anti-saw lock on the market. In general information, a valve with a valve operating temperature of t 450 ° C is called a high temperature valve. There is no uniform standard for the classification of high temperature valves for high temperature valves.
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Performance and classification
In the fluid delivery system, the valve is an indispensable control component, which mainly has the functions of regulation, diversion, anti-backflow, cut-off, and shunt. The valve is widely used in industrial and civil fields. High temperature valve is a commonly used type of valve. Its specific performance is as follows: good quenching performance, deep quenching; good weld ability; good absorption performance for impact, it is difficult to cause damage through violence; there is less tendency to temper brittleness and so on. There are relatively many types of high temperature valves, such as high temperature butterfly valves, high temperature ball valves, high temperature filters, high temperature gate valves, and the like.
High temperature valves include high temperature gate valves, high temperature globe valves, high temperature check valves, high temperature ball valves, high temperature butterfly valves, high temperature needle valves, high temperature throttle valves, high temperature relief valves, etc. Among them, the more commonly used are gate valves, globe valves, check valves, ball valves and butterfly valves.
First, the amount of thermal expansion
The difference between the thermal expansion of the material and the heat tolerance is an important condition for determining the difference in the amount of thermal expansion, so we should test the high temperature valve design activities.
High temperature valve
This should take into account the constraints of this condition. In order to allow the temperature in the spool to reach the same temperature as in the fluid, the heated high temperature fluid is then introduced into the valve with a very low temperature, so that the valve stem with a small side area can effectively dissipate heat. Because the heat dissipation conditions of the valve are different from other materials, especially in terms of expansion, although the heating is performed at the same time, the final expansion amount is completely different. Therefore, it is necessary to ensure the clearance of the valve operation, and also need to increase the range of control, so as to avoid the occurrence of component jam, and can significantly reduce the damage of the part due to temperature rise.
Second, the heat alternation
The medium has a great influence on the action of the parts in terms of heat exchange. For example, the contact between the valve seat and the guide may be loosened due to the change of the heat exchange of the medium, and the previously sealed function is lost. Therefore, when designing before, it is necessary to carry out strict seam welding of the valve seat and the supporting joint to ensure that its sealing function is not damaged. When designing, we also need to take into account the sealing selection effect under thermal alternation, so that the effect of heat exchange on the high temperature valve can be reduced at the source, and the consumption of parts can be avoided, thereby increasing the service life of the high temperature valve.
(1) Carefully check the tightness of the joint position to keep the parts in good working order.
(2) Regularly check the sprocket, chain and pressure gauge of the trolley, so that the matching components are kept clean and the lubrication performance is good, which fundamentally ensures the flexibility and reliability of the trolley at the actual action level. .
(3) Implement scientific maintenance and repair on the hydraulic system. Under normal circumstances, it is necessary to carry out inspection and maintenance on the hydraulic components and interface sealing conditions.
(4) Always wash and replace the filter cloth to ensure the filtration performance of the filter cloth.
(5) The hydraulic filter should be replaced once when the filter press is operated for the first time. When changing the oil, the hydraulic oil in the fuel tank and the cylinder should be drained and the tank cleaned. Continue to use oil for one month and then change oil once every six months to ensure safe, normal and reliable use of the filter press.
Valve packing principle
The sealing performance of the valve is an important indicator for evaluating the quality performance of the valve. Most of the regulating valves or universal valve stems and packing seals are now contact seals, which are widely used because of their simple structure, convenient assembly and replacement, and low cost.
Leakage at the stem and packing in the valve is a common phenomenon. The reason why the filler can play a role in sealing is that there are mainly two major sealing viewpoints, namely bearing effect and maze effect. The bearing effect of the packing means that between the packing and the valve stem, the packing is squeezed and the external lubricant acts, because the tension forms a liquid film on the contact surface of the valve stem, so that the packing and the valve stem are formed. Similar to the relationship of the sliding bearing, the packing and the valve stem will not wear due to excessive friction, and the packing and the valve stem are always sealed due to the presence of the liquid film.
The “maze effect” of the filler means that the surface of the valve stem is flat and cannot reach the microscopic level. The filler and the valve stem can only be partially fitted and cannot be completely fitted. There is always a very small between the filler and the valve stem. The gap is also asymmetrically assembled by the slits between the fillers, which together form a labyrinth belt in which the medium is throttled and depressurized multiple times to achieve a sealing effect.
Hardening of internal parts
First, enhance surface hardness and wear resistance
High-temperature valve internals often cause material to anneal or soften due to excessive temperature, which can easily cause scratches on the valve trim surface. To reduce this damage for high temperature valves, the hardness and impact strength of the trim inside the high temperature environment should be improved, and the ability to cope with erosion and corrosion should be appropriately increased. Ceramic or alloy can be used on the surface of the valve trim to increase the hardness and wear resistance of the valve trim surface, ensuring that the valve trim can play its due role in high temperature environment and prolong its service life.
Second, the thickness of the weld overlay
In order to achieve the hardening treatment of the high temperature valve internals, it is also necessary to confirm the thickness of the weld overlay. Through relevant experiments, it can be determined that the optimum thickness of the surfacing layer should be above 4 mm. Such a thickness can better isolate the high temperature of the external environment, reduce the influence of external high temperature on the internal materials, and ensure the service life of the valve internals.
Third, the principle of compliance
The first thing to pay attention to in the design process of high temperature valves is the choice of materials. Reasonable materials can avoid some accidents and prolong the service life of valves. Temperature factors can also have an effect on the use of the valve, so temperature factors should be taken into account during the design process. At temperatures above 280 degrees Celsius, an extended bonnet structure should be used to provide a lower temperature environment for the packing. When the temperature is greater than 350 degrees Celsius, the gap between the moving parts should be appropriately increased to ensure a higher hardness of the sealing sub-surface. When the temperature exceeds 450 degrees Celsius, the threaded sealing ring should be sealed to reduce the possibility of loosening and prevent leakage. When the temperature exceeds 500 ° C, the guide sleeve with the higher hardness surface and the guide section should be used to weld the guide sleeve to the joint of the support.