The working pressure of the existing single hydraulic prop is 28.5 MPa; the opening pressure of the upper working pressure safety valve is 31.5 MPa; the rated working resistance of the prop is 300 kN. Assuming that the pressure of the hydraulic cylinder is lower than 5 MPa, it shows that the hydraulic cylinder is at a low-pressure alarm working pressure. For a hydraulic cylinder with a diameter of 100 mm, the working lifting force F is:
That is, the design adopts a spring coefficient k range of 3000 to 4000 kN / mm, which is guaranteed to be within the working resistance range of the spring.
When assembling, first set the pretension force to F = 30 kN. The initial force of this setting overcomes the spring pressure and deforms. When the compression force presses the top cover into, the connecting wire is embedded.
Its role is to use a certain pressure during assembly to assemble the spring with the designed initial preload, which is also the pressure when the hydraulic cylinder is not in operation. At this time, the column head and the top cover are in a pressureless state that relaxes when extended, and the alarm display is exposed external.
When the high-pressure working medium is injected, the inside shows a high-pressure state. Due to the pressure, the column head and the top cover are at the minimum stroke, and the alarm display part is hidden inside the top cover.
