How to judge the fault of high-pressure cleaning motor assembly of papermaking machinery parts?

Fault judgment method of high pressure cleaning motor assembly of papermaking machinery

> Description: The assembly is composed of driving motor and high-pressure cleaning pump body. The paper-making workshop is high in humidity, the pulp splashes and there is water impact. The faults are divided into electrical fault, mechanical fault and pump body load fault. The judgment is as follows: first, visually observe the appearance → listen to the sound → measure the data → distinguish between the motor body fault and the pump load fault. It is forbidden to disconnect the junction box with electricity, and the power failure is carried out before overhaul.

I. Visual inspection of appearance (preliminary investigation)

1. Motor body

-The shell is free of water, pulp accumulation, junction box seepage, aging and cracking of sealing ring; The terminal is blackened, the cable is broken, the grounding is loose, and there is a high probability of water short circuit and poor contact.

-The surface of the motor is abnormally hot, and the paint on the shell is discolored, resulting in overload, blocked rotation and poor heat dissipation.

-There is no leakage of lubricating oil in the motor end cover and bearing position. The leakage of lubricating oil represents the failure of bearing seal.

2. Pump and transmission parts

-Cracking, fragmentation and excessive clearance of coupling elastomer; Loose anchor bolts, slurry accumulation, corrosion and deformation of the base will cause vibration and abnormal sound.

-The flange of high-pressure pipeline leaks and seeps, and the pressure in the pump will cause motor overload.

3. On-site working conditions: Check the alarm code of the control cabinet and the alarm records of overload, overcurrent, phase loss and overheating.

Second, listen to the abnormal sound and distinguish the fault categories.

1. Buzzing and muffled, not rotating: there is a buzz when the power is on, and the shaft disk does not move. High probability of phase loss, winding short circuit, pump stuck and locked; First turn off the power and turn the car. If the car doesn't move, it is mechanically stuck. When the disk is moving, it is biased towards electrical phase loss and winding failure.

2. Periodic metal rubbing sound: bearing is damaged, ball is worn and cage is broken; The higher the rotating speed, the greater the noise, accompanied by heating and vibration.

3. Impact and knocking sound: the coupling elastomer is damaged, the coaxiality deviation is large, and the anchor is loose; Load impact, high-pressure pump pressure fluctuation.

4. Sharp howling: the bearing lacks oil for dry grinding; Or that belt of the belt drive slip.

5. There is no obvious abnormal sound, but the current is large and the output is insufficient: most of them are internal wear of the pump and damage of the plunger/valve, which belongs to the load side fault, and the motor itself is not necessarily damaged.

> Distinguish the key points: power-off manual assembly

-Heavy turning, sticking and friction points: mechanical failure (damaged bearing, stuck pump, foreign body stuck pump)

-The turning car rotates smoothly without resistance: the fault is biased towards electricity (winding, phase loss, frequency converter problems)

Three, electrical detection and judgment (multimeter, megger)

1. Insulation resistance test (most importantly, high-frequency failure in wet environment of papermaking)

Power off and discharge, measure the insulation of three-phase winding to ground by megger.

-The insulation resistance is very low, close to 0MΩ: the winding is wet and flooded, and the winding is short-circuited by leakage; Water inflow in papermaking workshop is the cause of high incidence.

-Insulation value is low but not zero: the motor is damp, so it can be dried and retested; It is still low after drying, and the winding insulation is damaged.

2. Three-phase winding resistance measurement

When measuring the three-phase DC resistance of U/V/W, the deviation of the three-phase resistance is obviously large, which indicates that the winding turns are short-circuited and the terminals are virtually connected.

3. Check the control cabinet current with load

-Three-phase current is too large at the same time: overload, heavy pump load, pipeline pressure suppression and mechanical sticking.

-Three-phase current imbalance: lack of phase, virtual connection of wiring and partial damage of winding.

-Large no-load current: motor winding failure; No-load normal one-load current surges: the problem lies in the high-pressure pump load.

> note: for inverter drive models, give priority to inverter alarms: overcurrent, grounding fault, overheating, and output phase loss.

Fourth, distinguish: motor body fault VS high-pressure pump load fault

Many times, it is not the motor that is broken, but the pump body fault that drags the motor down:

| Phenomenon | Fault bias |

| --- | --- |

| Disconnect the coupling, separate the motor, and the motor rotates smoothly; When the pump is connected, it will not turn/the current will surge | The high-pressure pump fails, the plunger inside the pump is stuck, the valve group is stuck with foreign matter, and the pump is corroded and stuck |

| Dismantle the pump load, and start the motor alone, but the noise, heat and current are still abnormal | The motor body is faulty, and the bearings and windings are damaged |

V. Typical Fault Phenomena and Judgment

1. The motor frequently reports overload tripping.

(1) pump pipeline blockage, check valve failure caused by pressure; ② Poor alignment of the coupling; (3) the bearing damage resistance becomes larger; (4) motor winding be affected with damp; ⑤ The power supply voltage is unstable.

2. The motor is overheated and tripped after running for a period of time, and can be started again after cooling.

-The inlet water of the junction box is affected with damp, and the bearing is short of oil and worn; Pump load continues to be too large; The heat dissipation surface is covered by paper paste, and the heat dissipation becomes worse; The built-in temperature sensor of the motor is damaged and gives false alarm.

3. The motor has output, but the pressure of high-pressure cleaning water is insufficient.

The motor is in good condition with a high probability, and the fault points are inside the high-pressure pump: the plunger is worn, the check valve is damaged, the seal is damaged, and the motor is dragged down and the current is increased.

4. The operation vibration is large.

Loose anchor, slurry accumulation deformation of base, aging of coupling elastomer, bearing damage and large pump pressure pulsation.

5. Trip grounding protection as soon as it is started.

The winding is grounded by water, and the cable is damaged and grounded.

Six, the paper-making site specific fault incentives (easily overlooked)

1. The washing water splashed into the junction box and end cover of the motor, and the wet environment caused the winding insulation to decrease, which was the highest fault of this part.

2. The pulp impurities enter the high-pressure pump, causing the pump to jam and directly dragging the motor.

3. Paper pulp is piled up on the base, and the gasket is lost after maintenance, which will damage the bearing in a short time.

Seven, simple troubleshooting sequence

1. Check the alarm record of the control cabinet →2. Visually check the water seepage, slurry accumulation, bolts and couplings →3. Turn the car manually to judge the sticking →4. Measure the insulation with a megger, and measure the winding resistance with a multimeter →5. Disconnect the coupling, test the motor no-load and the pump load respectively, and locate the fault in the motor or the pump.