In daily applications, pneumatic hoists may encounter fault points of leakage protectors that cannot be found and occupy a lot of working time. 

Based on practical work, the editor of Hebei Mutian Pneumatic Hull Factory has summarized four online query methods for leakage protectors, which are for reference only.

1. Visual inspection method

The inspection staff conducted a specific analysis of the fault situation of the pneumatic hoist, and conducted visual inspections of the maintenance area, including leakage protectors and the line machinery and equipment being maintained, in order to identify the fault point. 

During the inspection, the main focus should be on inspecting complex areas such as corners, branches, and intersections of the line, as well as high-risk points for faults. 

Simple and easy to operate, suitable for searching for significant fault points, such as ground mounted transmission line disconnection, contact between suspended wires and transmission lines, and incorrect wiring.

2. Trial delivery usage

Disconnect the power supply of the pneumatic hoist switch first, then dismantle all the wires on the load side of the zero sequence transformer of the leakage protector, and then connect to the switch power supply. 

If the protector still cannot be put into use, it is a fault of the leakage protector itself and should be replaced or repaired. 

If everything operates normally, the protector is not faulty, and then investigate whether the pneumatic hoist fault occurred in the distribution box or in the internal and external wires.

The specific processing steps are as follows: first, disconnect the switch power supply from the outgoing lines of various groups or the load side of DC contactors. 

If it cannot operate, it is a fault on the distribution box. 

It is necessary to check whether the insulation layer of various electrical equipment, instrument panels, and other machine equipment is good, and whether the wiring is appropriate. 

If everything operates normally, it indicates that there is no fault on the distribution box. 

After determining that the fault occurred on the inner and outer lines, the line division enumeration method can be used to locate the fault point.

3. Line exclusion method

When it is determined that the fault point occurs in the internal and external lines, the various branch lines of the bottom voltage power grid can be disconnected in the order of "first main pole, then branch line, and then tail end". 

Only the main line can be tested and closed. 

If there is no fault in the main line, then the main line can operate normally. 

Subsequently, the branch and tail end funds will be put into operation. 

When funds are invested in the operation of which line, the protector will generate a posture, and the fault point will be located on which line, where the pneumatic hoist fault point can be centrally searched.

4. Value comparison analysis method

Rely on the pneumatic hoist instrument panel to accurately measure the circuit or machine equipment, and compare the measured standard value with the original standard value to identify the fault point. 

It must be emphasized that when the insulation layer of the neutral point of the line is lowered or the neutral point of the machine equipment is grounded, it is very easy to cause frequent tripping of the overall maintenance, while the secondary protector does not trip. 

When dealing with the tripping of the secondary protector, it is not allowed to use the secondary protector by exchanging the phase line with the neutral point. 

The machine equipment should be immediately dismantled repeatedly with wire connectors.