Common troubles of diesel engine pump and their solutions

Article provenance：Hai Rui ZhonglianPopularity：Publication time：2020-03-24 09:21

Common troubles of diesel engine pump and their solutions

Unable to start

First, check the power supply: whether the connector is firm; whether the switch is tight; whether the fuse is blown; whether the three-phase power supply is equal. In case of disconnection, poor contact, fuse fusing and phase loss, the cause shall be identified and repaired in time. Secondly, check whether it is the mechanical failure of the pump itself. The common reasons are: the packing is too tight or the impeller and pump body are stuck by debris; the pump shaft, bearing and reducing ring are rusted; the pump shaft is severely bent. Remedial measures: loosen the packing, dredge the water tank; dismantle the pump body, remove debris and rust; dismantle the pump shaft to correct or replace it with a new one.

Diesel engine pump heating

Causes: the bearing is damaged; the clearance between rolling bearing and bracket cover is too small; the bending of pump shaft or two shafts is not concentric; the tape is too tight; there is lack of oil or poor oil quality; the balance hole of impeller is blocked and the impeller is unbalanced, which increases the thrust on one side. Removal method: replace the bearing; remove the rear cover, install the gasket between the bracket and the bearing seat; investigate the concentricity of the pump shaft or adjust the concentricity of the two shafts; properly adjust the belt tightness; add clean grease, which accounts for about 60% of the bearing clearance; remove the blockage in the bearing B. Balance hole.

Diesel pump can't pump water

The reason is that there is air in the pump or water inlet, or the bottom valve is not closed strictly, resulting in unsatisfactory water, serious water leakage of vacuum pump packing, and the gate valve or valve is not closed strictly. Elimination method: first raise the water pressure, then fill the pump body with water, and then start the machine. At the same time, check whether the return valve is tight, and there is no leakage in the pipe and joint. If air leakage is found, apply lubricating oil or mixing paint on the joint after removal, and tighten the screws. Check the oil seal ring of pump shaft. If it is seriously worn, replace it with new parts. Pipe leakage or leakage. The nuts shall not be tightened during installation. If the leakage is not serious, the cement can be coated at the place where the air leaks or leaks, or the cement and asphalt oil can be mixed. Temporary repairs can be covered with wet mud or soft soap. If there is water leakage at the joint, the nut can be tightened with a wrench. If the leakage is serious, it must be reinstalled and replaced with a broken pipe; reduce the lifting force and press the nozzle of the pump into the water for 0.5m.

Severe vibration of diesel engine pump

There are several reasons as follows: unbalanced electric rotor; poor coupling; bearing wear and bending; loose and damaged rotating parts; adjustment, repair, reinforcement, straightening, replacement, etc. can be carried out separately.

Diesel pump motor overheated

There are four reasons. One is the power supply: the voltage is too high or too low. Under a specific load, if the voltage range is between + 10% and - 5% of the rated value, the motor will overheat; if the three-phase voltage of the power supply is asymmetric, and the three-phase voltage imbalance of the power supply is more than 5%, the power supply will overheat; if the phase is missing, experience shows that more than 85% of agricultural motors are burned due to the phase missing operation. Therefore, the phase loss protection device should be installed on the motor. Secondly, the reasons for the pump are: the power selection is not matched, the car is small, the motor is overloaded for a long time, so that the motor temperature is too high; the motor starts too frequently, and the quota is short-term or intermittent continuous operation. The starting time shall be limited, the thermal protection shall be selected correctly and used according to the quota on the motor. Third, the reasons for the motor body are: incorrect wiring, incorrect triangle and Y-shaped wiring, which causes the temperature of the motor to rise rapidly; short circuit of the stator winding, short circuit between turns or local grounding, local overheating of the motor, light time, serious insulation burning; broken bar or disconnection. In case of squirrel cage rotor failure, the temperature of the iron core will rise rapidly after the motor operates for 1-2 hours. Check the ventilation system for failure. Whether the fan is damaged, whether the rotation direction is correct, and whether the ventilation pipe is blocked; whether the rotor bearing is worn and cleaned eccentrically makes the stator and rotor core rub with each other, making the metal impact sound, the core temperature rises rapidly, and in serious cases, the motor smokes, or even the coil is burnt. Fourth, the working environment: the motor winding is affected with damp or dust, oil and other adhesion on the winding, resulting in reduced insulation. The insulation resistance of the motor shall be measured, cleaned and dried, and the ambient temperature shall be too high. When the ambient temperature is higher than 35 ℃, the motor temperature will be too high if the inlet temperature is too high. Like shadows and shadows. Note: in case of failure due to electrical reasons, electrician with professional qualification certificate shall be invited for repair. A person who knows nothing about it should not fix it blindly to prevent personal injury.

Deep well submersible pump

First, let's see how different the current run at this time is from the normal one. If it is smaller than usual (the base is 2 μ m of the normal current), problems such as impeller wear and pump head top blockage will occur. If the current is as high as usual, there will be water pipe leakage, water pipe leakage, pump body leakage and other problems. If the current is larger than usual, then it can be determined that the base is a problem of wear. In addition, if the cable breaks, the water volume is as large as usual, but the current will increase. The current of 3-phase 380V motor is generally 2.2A. As long as the above reasons are often found by maintenance personnel of deep well pump.

Cavitation phenomenon

Cavitation of the pump is caused by evaporation of water. Vaporization is the process of converting water from liquid to steam.

Manual diaphragm pump

Manual diaphragm pump
this is it. The vaporization of water is related to temperature and pressure. At a certain pressure, when the temperature rises to a certain value, the water begins to evaporate. If the pressure drops to a certain value at a certain temperature, the water will also evaporate. This pressure is called the vaporization pressure of water at that temperature. If the pressure in the local area is equal to or lower than the evaporation pressure corresponding to the water temperature during the flow, the water will evaporate there. After evaporation, many small bubbles of vapor-gas mixture will be formed. When the bubble flows from the low pressure area to the high pressure area, the bubble breaks under the high pressure, and the high pressure water flows to the space occupied by the original bubble at a very high speed, forming an impact force. Under the action of water hammer pressure, the metal surface is fatigued and damaged seriously. Therefore, the damage caused by the formation, development and fracture of bubbles is called cavitation.

Reasons for efficiency decline

1. Due to the erosion of water flow, the inner wall and impeller of the water pump flow channel become rough and uneven, and the impeller coefficient of the water pump flow channel increases. In addition, the water flow in the water pump is large, and the head loss increases. Reduced hydraulic efficiency.

2. Due to the use of drugs or water quality before the pump, the pump shell is seriously polluted or corroded. Serious scaling of pump casing can increase the wall thickness of pump casing by about 2ram, reduce the size of pump wall, reduce the volume of pump body, reduce the pumping capacity, rough flow path and increase the head loss. Reduce customer productivity and hydraulic efficiency.

3. The defects, cavitation, wear, corrosion and chemical erosion caused by the pump processing technology cause cavities or cracks in the pump flow, and vortex occurs in the flow process, resulting in energy loss. Reduced hydraulic efficiency.

4. Cavitation appears on the impeller surface. Due to the negative pressure generated when the blade is running on the water surface, when the pressure PK < PVA, after the steam bag and honeycomb surface are generated, the pump blade will generate cavitation under the action of electrochemical corrosion.

5. Volume loss and mechanical loss. Due to the long service time of the pump, the leakage and resistance caused by mechanical wear increase, reducing the volumetric efficiency and mechanical efficiency.

Due to the above reasons, the performance of the pump deteriorated. Reducing operating efficiency by 2 to 5 inches can significantly reduce pump efficiency by more than 10 inches.

Vibration cause analysis

The analysis of pump vibration causes a lot of vibration in buildings and pump rooms. Some factors are interrelated and influence each other. There are four main reasons.

Electrical aspects

The motor is the main equipment of the unit. This is often caused by the imbalance of magnetic force inside the motor and other electrical systems.

Vibration and noise. When the asynchronous motor is running, the radial AC magnetic pull between fixed rotors caused by the interaction of harmonic flux of fixed rotor teeth, or when the large synchronous motor is running, the inconsistent core of fixed rotor or the air gap difference in various directions exceeds the allowable deviation value, may cause periodic vibration and noise of the motor.

Mechanical aspects

The rotating parts of the motor and the water pump are unbalanced, rough, poorly installed, the unit shaft is asymmetric, the pendulum exceeds the allowable value, the mechanical strength and the rigidity of the parts are poor, the bearing and the sealing parts are worn and damaged, and the critical speed of the pump appears along with the device. Resonance such as natural frequency always causes strong vibration and noise.

Hydraulic aspects

The speed and pressure distribution at the inlet of diesel pump are uneven, the pressure pulsation at the inlet and outlet of the pump and the working fluid

Water pump control valve

Cleaning, deflection, deterioration, unfixed working conditions and various causes of pump cavitation are common causes of pump unit vibration. Starting and closing of water pump, opening and closing of valve, change of working conditions, emergency closing and other dynamic transition process caused by rapid change of water pipe and water hammer pressure often lead to vibration of pump house and unit.

Hydraulic and other aspects

The unreasonable design of the inlet flow channel of the equipment, the mismatch with the equipment, the inappropriate immersion depth of the pump, and the unreasonable start-up and stop sequence of the equipment will worsen the water inlet conditions, generate eddy current, cause cavitation or intensify the vibration. Unit and pump house. When starting the device to break the siphon vacuum cut-off, if the air in the hump is difficult, the siphon time is too long; the design of beating the door is unreasonable, when the door is opened, the door is closed, and the door is continuously knocked; the base of the pump and the motor sinks unevenly or the rigidity of the base is poor, which also causes the device vibration.

When the user selects the pump, it is better to go to the sales point approved by the Ministry of agricultural machinery and recognize the manufacturer. It is suggested that priority should be given to the purchase of water filled submersible pump, and the brand and product quality certificate should be specified. Do not buy "three no" (that is, no manufacturer, no production date, no production license) products, otherwise there will be problems, users will be helpless.

As a user, due to the limitations of professional knowledge, it is difficult to determine. The best way is to consult professional water pump, and it is also recommended to consult some old water pump users, especially those with similar use conditions. It would be wise to buy reliable, reliable and mature products. At the same time, the single-phase pump or three-phase pump shall be adopted according to the local power supply.

Noise cause
Pump noise may have the following aspects:

(1) The impact of the rotor on the cylinder block, the residual volume of the pump and the sound of the pressure oil at the exhaust dead angle;

(2) Impact of exhaust disc on seat and bracket;

(3) the echo and bubble burst in the box;

(4) Bearing noise;

(5) The noise produced by a large amount of oil and gas hitting the oil baffle;

(6) Others. For example, noise caused by transmission, fan noise of air and cold water pump, etc. ..

(7) Motor noise, which is a key factor.

Water leakage fault

1. The cooling water added by the operator to the cooling water radiator is sea water, which damages the internal water channel and external interface of the diesel engine. Therefore, the use of diesel engine must be strictly in accordance with the provisions of the diesel engine operation.

2. The radiator added by the operator has strong anti freezing and corrosion effect, causing damage to the components of the diesel engine channel.

3. The sealing ring is worn or aged, resulting in sealing and water leakage of the sealing surface.

Troubleshooting

1. After washing the radiator and the internal water channel of the engine body with clear water, remove the damaged parts of the diesel engine and replace the damaged parts of the diesel engine.

2. After assembly, commissioning and test, it is found that the diesel engine returns to normal and the fault is eliminated.

Water pollution

Methods of mixing water with fuel include issues such as water injection in the intake manifold and emulsification of diesel fuel.

Intake pipe spray

The main function of intake pipe water injection is to absorb heat and dilute fuel density. When a small amount of water enters the combustion chamber and is fully atomized, the oil drops break into smaller oil drops due to the "micro explosion" of water vapor, thus promoting the formation and combustion of the mixture. In the combustion process, because of the heat absorption of water, the maximum combustion temperature can be reduced. For example, injection of water and oil can reduce fuel density and further reduce the maximum combustion temperature, thus reducing NOx emissions. It should be noted that the storage tank should be antifreezed in winter and the water spray volume should be adjusted automatically according to the load.

Emulsified diesel oil

Diesel oil mixed with water, i.e. emulsified diesel oil, has good fuel atomization due to its "badge explosion" effect. The well promotes the air to form strong turbulence in the combustion chamber. The distribution of fuel and air is relatively uniform, resulting in the reduction of smoke and dust. The reaction of water and gas in water vapor also reduces carbon emissions. In addition, emulsified diesel can reduce the maximum combustion temperature, thus reducing the formation of NO x.

Maintenance plan

In the long-term operation of the pump, the bearing seat of the bearing frame of the pump is often worn, the bearing position is worn, the pump body is cracked, the pump is cavitating and flushing worn. After the above problems appear, the traditional solution of enterprises is to repair after welding or brush plating, but both of them have certain disadvantages: the thermal stress generated by repairing welding high temperature can not be completely eliminated, which may cause damage. Material and cause bending or breakage of components. Although brush plating is limited by the thickness of the coating, it is easy to peel off, and both of the above methods are metal repair metal, and can not change the "hard" fit relationship. Under the joint action of each force, it will still cause wear again. In the contemporary western countries, polymer composite repair methods are often used for the above problems, and it has excellent adhesion, excellent compressive strength and so on. The application of polymer material repair can not need disassembly and processing. The repair welding thermal stress has no effect and the repair thickness is not limited. At the same time, the metal material of the product has no franchise, which can absorb the impact and vibration of the equipment, avoid the possibility of re abrasion, and greatly extend the service life of the equipment parts. Enterprises can save a lot of downtime and create huge economic value.

Structure of centrifugal pump

When the pump rotor works at high speed, if the mass is unbalanced, it will produce a large centrifugal force when rotating, which will cause the vibration or damage of the pump. The balance of rotor is realized by the mass balance of its components (including shaft, impeller, sleeve, balance plate, etc.). Therefore, the static balance of the newly installed impeller should be checked. The specific methods are as follows:

(1) Put the impeller on the dummy shaft at the level of the static balance test bench. There are two tracks on the test platform, on which the dummy axis can roll freely.

(2) Mark the side of the impeller. If the impeller mass is unbalanced, the heavier side will always automatically turn to the lower side. Add a weight (using a surface stick or using a clamp to increase or decrease the iron sheet) to the symmetrical position of the heavier weight (i.e. the lighter side) until the impeller stops at any position.

(3) Weigh out the weight of the weighting block. The balance of the impeller can be achieved by reducing the weight of the heavier side of the impeller rather than the weight of the lighter side. When reducing weight, milling machine or grinding wheel can be used (when the amount of disassembly is not large), but it should be noted that the milling depth or grinding depth should not exceed 1 / 3 of the thickness of impeller cover plate. After static balance, the allowable deviation of static balance shall not exceed the product of impeller outer diameter and 0.025g/mm. For example, the allowable deviation for a 200 mm diameter impeller is 5g.

Disassembly and assembly of coupling

When removing the coupling, do not directly hit it with a hammer, cover it with a copper rod, and hit the hub of the coupling.

Water pump coupling

1. It is impossible to touch the outer edge of the coupling, because it is easy to break. The best way is to remove the coupling with tweezers. For small and medium-sized pumps, the coupling is easy to disassemble due to small interference fit. For larger pumps, the coupling has a great interference with the shaft, so the coupling must be heated during disassembly.

2. When assembling the coupling, pay attention to the serial number of the key (for the coupling with more than two keys). If you strike with a copper rod, you must pay attention to the part you hit. For example, when the end face of the axle hole is impacted, it is easy to shrink the axle hole, so that the axle will not pass through; when the outer edge of the wheel is impacted, the flatness of the end face is easily damaged, and when the contact is later corrected, the accuracy of the measurement will be affected. Academic degree. For couplings with high interference, they should be heated and reloaded.

3. The pins, nuts, washers and rubber pads of the coupling must be kept according to their specifications and dimensions to avoid affecting the dynamic balance of the coupling. Corresponding marks shall be made on connecting bolts and corresponding connecting pin holes to prevent dislocation.

4. The cooperation between coupling and shaft is generally transitional. There may be a small surplus or a small gap. For the hub with long coupling, because of its long shaft hole, a loose transition fit can be used. Due to rough surface processing, some of them will be left after assembly. If the coupling is too loose, which affects the concentricity of the hole and the shaft, it should be solved. It is not ideal to put a numb point or gasket on the shaft as a temporary measure.

Previous：Use of diesel engine water pump Next：Precautions for diesel engine water pump

Recommended products

Product Center

Long shaft fire pump

Long shaft fire pump Product Brief XBD / g-hrzl axial flow deep well fire pump (long shaft deep well f...