In the operation of truck-mounted cranes, winch malfunctions can pose significant challenges and disrupt the normal lifting process. Being able to accurately identify and diagnose these failures is crucial for timely repair and minimizing downtime. In this article, we will explore in detail the skills and methods for identifying truck-mounted crane failures specifically related to winch malfunctions.
Imagine a scenario where atruck-mounted crane owner is in the middle of a lifting operation. Suddenly, the winch motor stops rotating, and the crane is unable to lift or lower the load. However, other hydraulic mechanisms of the crane are functioning normally. This unexpected situation can be extremely perplexing and frustrating for the operator. The first step in troubleshooting is to carefully observe and analyze the symptoms. In this case, we notice that the pressure gauge shows 0 when the lifting mechanism handle is operated. This is a key indication that something is amiss within the hydraulic system specifically related to the winch.
To begin our diagnosis, we can rule out the possibility of a hydraulic pump malfunction. If the hydraulic pump were faulty, it would likely affect the operation of multiple hydraulic mechanisms, not just the winch. Moreover, when operating to the position where the two pumps are combined, if the winch were experiencing a problem due to the pump, it would typically slow down rather than completely stop working. Since other hydraulic mechanisms are working properly and the winch stops abruptly with no pressure indication, we can focus our attention on the winch circuit and its components.
The next step is to examine the relief valve of the winch circuit. The relief valve plays a crucial role in regulating the pressure within the hydraulic system. If it malfunctions, it can cause a loss of pressure and prevent the winch from operating correctly. We remove the main relief valve and conduct a thorough inspection. After cleaning and reinstalling it, if the fault persists, we need to dig deeper.
It’s important to note that some truck-mounted cranes have a remotely pilot-controlled main relief valve. This means that an additional component, such as an overwind solenoid valve, can influence the operation of the relief valve. When the overwind solenoid valve is energized, it can cause the relief valve to open prematurely, resulting in unloading and a loss of pressure in the winch circuit.
To test this possibility, we unplug the plug of the overwind solenoid valve. However, even after doing so, the fault still persists. This indicates that the problem lies elsewhere within the solenoid valve or its associated components. At this point, we take a more direct approach by drawing a constant power from the power supply and using it to directly push the solenoid valve. When we do this, we notice that the indicator light on the solenoid valve is on, but there is no audible clicking sound of the solenoid valve operating normally. This is a strong indication that there is an internal problem with the solenoid valve.
To further investigate, we completely remove and disassemble the solenoid valve. Upon inspection, we discover that the return spring of the solenoid valve is broken. This is a critical finding, as the broken spring causes the solenoid valve to malfunction. Under the influence of gravity, the iron core of the solenoid valve pushes the reversing valve stem to reverse its position. As a result, the winch circuit loses pressure, and the winch motor is unable to operate.
Once we have identified the root cause of the problem, the solution becomes clear. We replace the broken return spring with a new one of the appropriate specification. After reassembling the solenoid valve and reinstalling it in the truck-mounted crane, we test the winch operation. To our relief, the fault phenomenon is eliminated, and the winch is once again able to lift and lower loads smoothly.
In conclusion, when dealing with winch motor malfunctions in truck-mounted cranes, a systematic and methodical approach is essential. By carefully observing the symptoms, ruling out potential causes one by one, and conducting detailed inspections and tests of the relevant components, we can accurately identify the source of the problem. With the right skills and knowledge, even complex winch failures can be diagnosed and resolved, ensuring the reliable and efficient operation of the truck-mounted crane. Remember, patience and attention to detail are key when troubleshooting any mechanical issue.
