Troubleshooting the fault of container cranes being unable to move

The large container crane equipped with Clark HR-32470 (PPM Company) power shift transmission has faults such as inability to move or weak movement during use. We promptly eliminated the fault with the aid of simple diagnostic instruments such as pressure gauges.

1. Unable to walk

The inability to move refers to the situation where, when operating the electromagnetic shift valve of a certain gear, the transmission cannot transmit torque and the machine cannot move.

The possible cause could be: There is a fault in the circuit system; The distribution valve is faulty. The control oil circuit of the transmission is blocked or severely leaking. The clutch friction plates are severely worn or broken.

When encountering this phenomenon, you can first connect a pressure gauge to the clutch running pressure detection port at the top of the transmission, then start the engine and check the running pressure at this time (the design standard value of the running pressure for this machine is 1.69-1.96MPa). The detected situations generally include the following four types:

If the pressure is far below 1.69MPa, first check whether the oil is sufficient, then check if the pressure regulating valve is faulty (such as the pressure regulating spring being too soft or broken, etc.). If the pressure regulating valve is normal, disassemble and inspect the transmission and the traveling hydraulic pump. If the fault of low walking pressure still cannot be ruled out, then it is necessary to check whether there are any cracks in the oil supply pipe inside the transmission.

If the walking pressure meets the design standard, the walking control handle can be pushed to the fault position (assumed to be the forward I position), and the change in the pointer reading of the pressure gauge can be observed. If the pointer shows no response, it is certain that the pressure oil has not been connected to the forward I gear clutch hydraulic cylinder at all. Since this place is electrically controlled, the technical condition of the power supply should be checked first, that is, whether the electromagnets of the forward gear and I gear clutch control valves are normal. If the electromagnet is normal, then it is necessary to check whether the valve core of the forward gear or I gear clutch control valve is jammed, that is, to check the jamming condition of the slide valve. The jamming of the spool valve is mostly caused by the contamination of the hydraulic oil. The fault can be eliminated by cleaning and changing the oil. Wear or damage to the valve core can also cause the machine to fail to move. If all the above checks are normal, it may be that the pipelines leading to the forward gear and I gear clutch hydraulic cylinders are severely blocked.

③ If the pointer reading of the pressure gauge drops rapidly after the fault mode is engaged, and then slowly rebounds to a certain value (still far below 1.69MPa). Compared with other gears, if only the forward I gear and the reverse I gear have this phenomenon, it can be confirmed that the pipeline leading to the clutch hydraulic cylinder of the I gear is seriously leaking. If there is a fault in the clutch of gear II, III or IV, the diagnostic method is the same as this. If this phenomenon occurs in all four forward gears but not in the four reverse gears, it indicates that the pipeline leading to the forward gear clutch hydraulic cylinder is severely leaking. And vice versa. If it is impossible to diagnose by the elimination method by comparing the conditions of each gear, the exhaustive method can also be used for diagnosis. That is, after starting the engine, without using the walking control handle in the driver's cabin, power on the electromagnet of the control valve of the clutch hydraulic cylinder of a certain gear separately (note that it is powered on separately), and observe the change in the pointer reading of the pressure gauge. If the pressure drops rapidly and then slowly rises to a certain value (far below 1.69MPa), it can be determined that the pressure oil pipeline of the clutch hydraulic cylinder at this gear is seriously leaking. By separately testing the hydraulic oil travel pressure of the six clutches, the condition of the control oil circuit of each gear clutch can be accurately determined.

④ If the fault mode is engaged, the pointer reading of the pressure gauge drops rapidly and then slowly rises back to the standard value, but there is no upward trend. Judging from this phenomenon alone, it should be caused by severe wear of the clutch friction plates. The degree of wear of the friction plates can be diagnosed based on the time required for the pressure to rise. This diagnostic method is also known as the time lag test diagnostic method. When using this diagnostic method, the engine speed should be recorded, as only when the engine speeds are the same can the lag times be comparable. In addition, by checking the working fluid of the transmission to see if there are any fragments of friction plates or metal shavings in the fluid, a definite diagnosis can be made. To determine which gear of the clutch friction plate is severely worn, one can refer to the comparative exclusion diagnosis method and the exhaustive diagnosis method for severe leakage in the clutch pressure oil pipeline.

In conclusion, when a machine fails to move, the method of measuring the walking pressure can be adopted for diagnosis.

2 Weakness in walking

The so-called weak movement refers to the situation where the transmission fails to deliver the torque designed for each gear, that is, the transmission slips. Its symptoms are: a feeling of slippage when moving forward or backward. Atlas air compressor parts: The engine idles when starting or shifting gears.

The possible reason for this could be insufficient control of the main oil pressure. The clutch friction plates are worn. In addition, apart from circuit system failures and the jamming of the valve core of the distribution valve, all the reasons that cause the machine to be unable to move will lead to weak movement of the machine, only the degree varies.

According to the diagnostic method for the cause of the machine's inability to move, connect a pressure gauge to the clutch travel pressure detection port, start the engine, and observe the reading of the pressure gauge pointer. When the pressure value is lower than the standard value, the method for checking the cause of the fault is the same as that when the person cannot walk.

If the pressure value is consistent with the standard value, diagnosis and analysis can be made by operating the handles of each gear and comparing the changes in the pointer readings of the pressure gauge. The diagnostic and analysis methods for the walking weakness fault caused by leakage in the control pipeline and slippage due to wear of the friction plate are the same as those for the inability to walk fault, but the problems that occur are not as serious. If, after shifting to the previous gear, the pointer reading of the pressure gauge drops rapidly and then quickly returns to the standard value, while the movement is normal, but after a few minutes, the pressure drops again and the movement becomes weak, and when the control handle is pushed back to the neutral position, the pressure returns to the standard value after a few minutes, this phenomenon is generally caused by poor oil suction or insufficient oil. It is necessary to focus on checking whether the filter element is clogged. Whether the oil is sufficient.

The above fault diagnosis analysis, with the aid of simple diagnostic instruments such as pressure gauges, utilized the comparative elimination method and exhaustive method in mathematics. It has the effect of drawing inferences by analogy for the fault diagnosis of other models of hydraulic shift transmissions.