Created on:2021-07-16 09:03

Crawling and out of control failure of hydraulic system of steel coil transport trolley

Cause analysis and troubleshooting of crawling, out of control and non operation of hydraulic system of steel coil transport trolley

(1) Crawling and out of control failure

Symptoms: when the car descends longitudinally, it crawls and vibrates; After loading, the car moves back laterally, stops and even doesn't move at all.

① There are creeping and shock vibration phenomena after longitudinal descent, which are caused by two reasons.

a. When the orifice of the one-way throttle valve (3 in Figure o) is small, the impurities and dirt in the oil are easy to adhere to the orifice, which reduces the flow through the throttle valve and increases the pressure difference. The pressure pulsation washes the dirt away from the orifice and increases the flow through the orifice. So repeatedly, resulting in crawling failure.

b. The damping hole in the control valve (6 in Figure o) is blocked by impurities, which makes the setting pressure unstable and the system pressure fluctuates greatly, so that the motion of the trolley platform fluctuates greatly, accompanied by shock and vibration.

Troubleshooting: replace new oil, replace filter element, clean throttle valve and overflow valve.

② There are two reasons for this phenomenon.

a. Mechanical failure, such as foreign matter on the car wheel, wheel rotation will be stuck, stuck, track deformation and excessive resistance or obstacles. After investigation, it was ruled out.

b. When the trolley goes back horizontally, (12 in Figure o) reverses, the set pressure of the relief valve (8 in Figure o) is too low or close to the critical value, or the relief valve is stuck or jammed, it will cause pressure, no pressure or no pressure at the inlet end of the hydraulic motor (12 in Figure o), resulting in the phenomenon that the wheels of the hydraulic motor drive the trolley turn and stop.

Troubleshooting: the abnormal rotation of the trolley wheel is caused by the failure of the hydraulic system, so first of all, enlarge the oil return switch to the opening of the throttle valve (5 in Figure o), and tighten the pressure regulating bolt of the relief valve (8 in Figure o) from the outside to the inside (at this time, the pressure should be increased). If it is invalid, it can be concluded that the spool of the relief valve is stuck (a in Figure q), and the relief valve needs to be replaced. After the relief valve in the coil car of the auxiliary line is installed as a spare part, the movement is normal immediately, indicating that the judgment is accurate.

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(2) Cause analysis and troubleshooting of no action fault

Symptoms: when the repaired hydraulic components (relief valve, balance valve) are installed in the hydraulic system of the car, after running for a period of time, suddenly the car doesn't move in the transverse direction, and the movement in other directions is normal.

Analysis: when the car suddenly moves horizontally, it doesn't move, but it moves normally in other directions, which indicates that the system circuit (13 in Figure o) and the system pressure regulating valve (13 in Figure o) are in normal operation. 6) The hydraulic motor (12 in Figure o) is intact; Only when the electromagnetic directional valve (2 in Figure o) is suddenly stuck and the direction is not in place, the throttle port of the oil return one-way throttle valve (4 in Figure o) is suddenly blocked, the oil flow channel is blocked, the spool of the overflow valve (7 in Figure o) at the front end of the hydraulic motor inlet is suddenly blocked, the high-pressure oil is unloaded, and the hydraulic motor inlet does not rotate due to no pressure, Only then can the phenomenon of sudden lateral advance not move occur.

Troubleshooting: manually check whether the solenoid valve (2 in Figure o) spool action is sensitive, that is, to increase the opening of the throttle valve (4 in Figure o); If it is still invalid, remove and check the relief valve immediately (7 in Figure o). Results a small iron sheet was found stuck in the main valve core end of the relief valve (see Figure B in Q), which caused the relief valve to unload and the hydraulic motor inlet could not rotate the loaded trolley wheel due to no pressure. After removing the small iron sheet, the overflow valve fault is removed, and the trolley returns to normal.

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