Fault has been occurring ever since we started operations but it didn't happen often so we didn't do further research until it hit us twice in a week causing my boss to panic and ended giving me the task to find the root cause of the fault.
Figure 1. The very moment when fault occurred.
In this particular case the fault occurred due to operation of the selector switches at the control panel PA.1. This happened because the placement of two switch selectors (clutch mode switch and operation mode switch) in the operator panel were side to side making possible for the operator to make the wrong selection. Usually the attention of the operator is focused on the CCTV monitor or in the HMI panel.
Figure. Usual operator posture
Figure. Original placement of switch selectors in control panel PA.1. Clutch mode and Operation mode switches are in the middle side to side.
Figure. New placement for switch selectors. Now "Clutch Mode switch" and "Operation Mode switch" are as far as they can be. It makes hard for the operator to get the wrong switch.
Additionally, due to the research done, other causes for this fault were found:
* Inductive sensors in valve 57. This is the first thing we inspected since it is linked to the description at the fault. We checked wiring connections and we watched the functioning during hoist operations.
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| Figure. Inductive sensors at v57 valve in GP. |
* Clutch and sprag limit switches. Somehow during investigation somehow moved one of the limit switches at the clutch mechanism and this v57 fault appeared. Then we tried the same with the sprag limit switch and gave us the same result. I wonder that if these limit switches are loose you may have this fault too.
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| Figure. Manipulation of clutch limit switches. |
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| Figure. Sprag limit switch. |
