DIY submersible pump repair

Recommendation points

• Clearing blockages
• Checking the power line
• The difference between a rod structure and a monolithic
• Extraneous noise during operation
• Revision of the motor part
• Revision of the pumping mechanism

Rare well pumps can be absolutely reliable. Some breakdowns can be corrected locally with your own hands, our instructions will help in this matter with a description of typical malfunctions, their diagnosis, elimination, as well as maintenance recommendations.

Clearing blockages

To say that the water quality in the well is far from ideal is to say nothing. Even if the pump is equipped with a filtering device, it will need periodic cleaning, and the coarse depth filter will not be able to retain the fine fraction settling on the impeller and housing.

Most borehole pumps break down precisely due to blockages of the working part by sand and limestone deposits. At least once every two years, you need to remove the pump from the well, flush it and clean the surfaces of functional elements from contamination. Do not be confused by the small amount of deposits: after a plaque has appeared on the surface, further accumulation of deposits occurs in an avalanche-like manner.

The pump room, that is, the lower part of the device, as well as the water flow channels, are subject to cleaning. The pump can be divided into two halves after removing the protective mesh in the central part. It is necessary to unscrew 4-6 nuts from the studs that tighten the flange connection. Then one or two locking screws are unscrewed, holding the flange from unscrewing, and then the flange itself is unscrewed from the glass. In pumps of a monolithic type, you need to unscrew the plug of the bottom filter, for this, the nut of the outlet pipe should be clamped in a vice, the plug itself is easily torn off with a belt wrench.

The pumping of water in deep-well pumps is due to several impellers sequentially mounted on the shaft. They must be removed, remembering the assembly order, and then cleaned of dirt along with the inner surface of the sleeve, mesh and other elements in contact with water. The surfaces of the parts should not be cleaned mechanically to avoid scratching. It is better to use gentle household chemicals for descaling and rust converters, and then wipe off the remaining plaque with a soft synthetic brush or the rough side of a dish sponge.

Checking the power line

Primary diagnostics of the pump includes pulling it out of the well and short-term “dry” operation with control of shaft rotation. In this case, you should pay attention to the nature of the hum of the engine: it should not experience additional load, crackling, rustling and uneven hum are categorically unacceptable.

Please note that you need to check the pump without reconnecting to the mains. The length and cross-section of the wire should be the same as in everyday work. This is due to the fact that the voltage drop on the power line of more than 30-50 meters can be very significant, besides, it is impossible to exclude a fracture of cores, breakdown of insulation and malfunction of protective and starting automatics.

Damaged network cable insulation

First of all, disconnect one of the power leads from the pump terminal block and measure the voltage – it should not be lower than the permissible rating values. If the voltage drop is too strong, then replace the cable with a better or larger section. Also in a fully disconnected cable, measure the resistance between the conductors and each of them separately. In the first case, the multimeter will not give readings in any of the ranges, the opposite indicates insulation breakdown, which is typical for PVA brands insulated with foamed PVC compound. The value of the resistance of the current-carrying conductors themselves will bring more clarity to the problem of voltage drop, will help to eliminate the influence of transition resistances at the terminal clamps.

Also, do not forget to find out if the circuit breaker is out of order. Its rating is precisely matched to the pump so that at the slightest overload, the power is turned off, preventing damage to the motor part. Mainly used are circuit breakers with a tripping characteristic “A”, the rating is selected and regulated both by the pump power and by the supply voltage and line length.

The difference between a rod structure and a monolithic

As mentioned, there are two types of borehole pump designs. They are most easily distinguished by the location of the engine: in monolithic ones, it is located in the upper part of the common housing and is washed by a stream of water. In rod versions, the motor module is mounted from below through a flange connection, the pump and motor shafts are connected by a splined coupling. Water intake is carried out in the middle part of the casing through the mesh and therefore such pumps are more susceptible to dry running at a low dynamic level of the well.

The main advantage of the rod design is the ability to determine the cause of a malfunction without thorough disassembly. After disconnecting the two parts, the stroke and play of the shaft in each of them can be checked separately, while for monolithic pumps, all the impellers must be removed first..

The device of a sucker rod pump. А – pumping part: 1 – outlet branch pipe; 2 – pump shaft; 3 – compensation ring; 4 – a sealing ring; 5 – suction chamber; 6 – splined coupling; 7 – motor shaft; 8 – protective mesh; 9 – impeller; 10 – impeller bearing; 11 – flow channel; 12 – check valve. B – engine: 13 – sand drainage channel; 14 – seal; 15 – stator winding; 16 – bearing for removing axial load; 17 – thrust bearing; 18 – pressure equalization system; 19 – rotor; 20 – grease; 21 – pump shaft; 22 – clutch; 23 – network cable

There are also other design solutions. In particular, screw pumps are designed like rod pumps, but the water intake is carried out at the top, while the principle of operation is somewhat different. The main advantage is the ease of servicing the pumping part: the auger and, if necessary, the damper clutch can be replaced in 10-15 minutes. It is enough just to unscrew from 3 to 5 bolts on the upper end and remove the outer sleeve of the pumping unit. It is important to remember that screw pump motors can run dry almost indefinitely, but only if the auger is removed..

Screw (screw) borehole pump

Extraneous noise during operation

Immediately after purchasing the pump, it is very important to carry out several short-term dry-running starts and one or two long-term starts with immersion in a container with water. At the same time, the nature of the noise during operation is evaluated and remembered.

A change in the tone of the sound may indicate a mismatch in the supply voltage. With a strong drop, the hum of the engine will be lower and strained, if such a pump is lowered into a well, it may simply not raise the water to the desired height, even when it is fully operational. Too high tonality may be due to the fact that the pump does not transmit rotation to the impellers or other working element. The reason may be a bursting shaft, worn-out splines at the connection of the rods or broken seats of the impellers..

Howling (singing) during operation is a characteristic sign of increased friction in thrust bearings. Broken separators may indicate a crackling sound or severe vibration. An extreme case – jamming of the shafts, while the pump motor is straining to hum, but does not rotate.

Revision of the motor part

Deep well pumps are equipped with a single-phase, mostly brushless asynchronous motor. The wiring diagram has a starting capacitor. The stator of the electric motor has a monolithic attachment to the body, often it is filled with epoxy compound.

In pumps of a monolithic design, the engine must be squeezed out of the glass by pressing on the outlet of the outgoing pipeline connection with the impellers removed. In rod pumps, the motor part is disconnected when the two halves are undocked, in screw pumps – after removing the working screw. In all cases, the internals of the engine (capacitor, connection terminals) can only be reached after removing the sealed plug. It is fixed with 2–3 screws on the side surface of the sleeve and a strong retaining ring. In some pump types, the plug may require the use of a special puller..

Well pump motor stator

All borehole pump motors are filled with oil that serves as a lubricating, cooling and dielectric function. Special edible oil is used, but it is commercially available. Signs of poor quality can be a cloudy color of the oil when mixed with water, darkening or the presence of mechanical impurities, as well as an insufficient level. If the oil is normal, it must be drained into a clean, dry container, leaving the motor housing for 15–20 minutes until the residues are completely drained from the walls. Insufficient oil filling of the engine indicates wear of the stuffing box seals.

In addition to spoiled oil, worn bearings can be the cause of engine malfunction, which is determined by backlash and freewheel noise. If the pump has been operated for a long time in extreme conditions, the shaft may be twisted (twisted), the insulation of the windings may overheat. Burnt stators are practically beyond repair, but they are easy enough to replace.

Burning of the stator winding due to water entering the motor

Revision of the pumping mechanism

In addition to dirt, the main reason for the pumping mechanism breakdown is long dry running. Due to the lack of liquid, the blocks of centrifugal impellers get very hot and sintered, so the only repair option is to replace them. The same is the case with the auger and landing sleeves. Also, with jammed impellers, the shaft can rotate in the landing holes, and in powerful pumps, its deformation and even destruction.

In screw pumps, screws and bushings are consumables; they are changed every 3-5 years, depending on the intensity of use. The main reasons are natural aging of elements and exposure to small abrasive particles.

Screw and sleeve for auger pump

Let us draw your attention to the fact that the parts of borehole pumps have a high accuracy of fit, so that the cleaned mechanism is easy to assemble and disassemble. If, during assembly, the parts do not fall into their places freely, then the order of installing the elements is violated. There are specific design differences in different pump models, but the basic recommendations for self-repair and disassembly for revision are always described in the user manual, which often includes an assembly diagram..