This article introduces a heat insulation effect test of high-pressure and ultra-high temperature valve body and the test device and operation method of the matching relationship between the pressure of the hydraulic actuator and the medium temperature and pressure.
The high-pressure and ultra-high temperature hydraulic control globe valve (the thermal valve, Figure 1) is the key device installed in the hypersonic (M>10) wind tunnel test device. The maximum working pressure of the valve is 12MPa. The nominal diameter is DN500 and the maximum working temperature is 900℃. The medium is high-temperature dry air. According to the working conditions and system requirements, when the valve leaves the factory, in addition to the strength, high pressure seal and low pressure gas seal tests according to API598 standards, the heat insulation test and the matching test of the hydro-cylinder of the actuator and the working pressure and temperature of the medium also need to be carried out. The requirement for the shell thermal insulation test is that when the medium temperature is 900℃, the outer surface temperature of the shell is smaller than or equal to 80℃. According to the requirement for matching between hydro-cylinder and the medium parameters, the medium pressure are 1MPa, 2MPa, 4MPa, 6MPa, 8MPa, 10MPa and 12MPa respectively. There are 7 grades, and the medium temperatures are 505℃, 611℃, 715℃, 809℃and 900℃. The medium pressure is proportional to the cylinder pressure, which is easy to calculate. However, the temperature of the medium will affect the hardness of the seal pair (STL) and the seal pressure of the seal pair will be affected. These data cannot be found in the valve design calculation manual and related documents. Only through tests can we determine the matching relationship between the hydro-cylinder pressure and the media parameters. The pressure of the hydro-cylinder must overcome the acting force of the medium, the necessary sealing of the sealing pair and the friction between the valve stem and the packing. If the pressure of the hydro-cylinder is too high, the sealing surface will be crashed, affecting the service life of the valve. If the pressure of the hydro-cylinder is too low, the sealing pair cannot be sealed and the valve cannot work normally. Therefore, it is very important to select and adjust the hydro-cylinder pressure correctly to achieve a reasonable match.
The test method of the thermal valve is shown in the Figure 2. The first is the heat insulation effect test of the shell. There is a thermal insulation layer with a thickness of 100mm between the inner cavity of the valve and the inner wall of the valve body. The thermal insulation layer is mainly made of two materials. Innermost layers are 3 layers of thermal insulation sleeves with thicknesses of 8mm, 2mm and 1mm. Each layer has vent holes with different diameters. The total vent area is about 0.03%; the largest hole is p10mm, and the smallest hole is p3mm. The metal sleeve is wrapped with stainless steel wire mesh, and the mesh is wrapped with 3 layers of silica gel aluminum fiber felt. The gaps on the outside of the felt are stuffed with aluminum silicate fiber cotton. This not only ensures that the insulation layer is ventilated, but also ensures that the fibers are not taken away by the airflow. In the heat insulation test, a resistance wire heater is placed in the cavity of the valve body, and the insertion temperature is increased to 900℃. After one hour, if the surface temperature of the valve body does not exceed 75℃, the test result is qualified.
Figure 1 High pressure and ultra high temperature hydraulic control globe valves or thermal valves
Figure 2 Hot sealing tests of thermal valves
1. Temperature indicators 2. Pressure tests for blind plates at inlets 3. Thermocouple 4. Contact temperature controllers 5. Electric heaters 6. Valve bodies 7. Oil cylinders 8. Blind plate insulation layers 9. Pressure tests for blind plates at outlets 10. Air outlets 11. Needle valves 12. Distilled water bottles 13. Flow meters 14. Air inlets 15. Pressure gauges 16. Connecting pipes 17. Deep control valves 18. Gas cylinder regulating valves 19. Nitrogen cylinders