The working pressure of the existing single hydraulic prop for mine is 28.5mpa; The opening pressure of the operating upper limit pressure relief valve is 31.5mpa; The rated working resistance of the pillar is 300 kN. It is assumed that the pressure of the hydraulic cylinder is lower than 5 MPa, indicating that the hydraulic cylinder is under low-pressure alarm working pressure. For the hydraulic cylinder with a diameter of 100 mm, the lifting force F is:
That is, the spring coefficient k can be used in the design range of 3000 ~ 4000 kN/mm to ensure that the working resistance of the spring is within the range.
During assembly, first set the preload as F= 30kn, the initial force to overcome the spring pressure and deformation, and the compression force to press the top cover and insert the connecting wire.
Its function is to use a certain pressure during assembly to assemble the spring to design the initial pre-tightening force, which is also the pressure of the hydraulic cylinder when it is not working. At this time, the cylinder head and the roof are in the no-pressure state of relaxation during elongation, and the alarm shows that the outside is exposed.
When the high pressure working medium is injected, the internal state is high pressure. Under the action of pressure, the stigma and the top cover are in the minimum travel, so the alarm display part is hidden in the inside of the top cover.
