What is the main working principle of the centrifugal pump?
The motor drives the impeller to rotate at a high speed, causing the liquid to generate centrifugal force. Due to the centrifugal force, the liquid is thrown into the side flow channel and discharged out of the pump, or into the next stage of the impeller, so that the pressure at the impeller inlet is reduced, and the pressure acting on the suction liquid forms The pressure difference, the pressure difference acts on the liquid suction pump, because the centrifugal pump rotates continuously, the liquid is continuously sucked or discharged.
2. What are the functions of lubricating oil (grease)?
Lubrication cooling effect, flushing effect, sealing effect, damping effect, protection effect, unloading effect.
3. Which three levels of filtering should the lubricating oil go through before use?
The first level: between the original lubricating oil barrel and the fixed barrel;
The second level: between the fixed oil drum and the oil can;
The third level: between the oil can and the refueling point.
4. What is the "five fixed" of equipment lubrication?
Fixed point: refuel at the specified point;
Timing: Add oil to the lubricated parts at the specified time and change the oil regularly;
Quantitative: add fuel according to consumption;
Qualitative: Choose different lubricants according to different models, and keep the quality of the oil qualified;
Personnel: There must be someone responsible for each refueling part.
5. What is the hazard of water in the lubricating oil of the machine pump?
Moisture can reduce the viscosity of lubricating oil, weaken the strength of the oil film, and reduce the lubricating effect.
Water will freeze below 0℃, which will seriously affect the low-temperature fluidity of lubricating oil.
Moisture can accelerate the oxidation of lubricating oil and promote the corrosion of low-molecular organic acids to metals.
Moisture will increase the foaming of lubricating oil and make lubricating oil prone to foam.
Moisture can rust metal parts.
6. What are the maintenance contents of the pump?
Conscientiously implement the post responsibility system and equipment maintenance and other rules and regulations.
The equipment is lubricated to achieve "five fixed" and "three-stage filtration", and the lubricating equipment is complete and clean.
Maintenance tools, safety facilities, fire-fighting equipment, etc. are complete and in good order.
7. What is the standard for common shaft seal leakage?
Packing seal: light oil less than 20 drops/min, heavy oil less than 10 drops/min
Mechanical seal: light oil less than 10 drops/min, heavy oil less than 5 drops/min
10. Why can't the centrifugal pump disc start when the car is not moving?
The centrifugal pump disc does not move, indicating that there is a fault inside the pump. The fault may be something stuck in the impeller or excessive bending of the pump shaft, or the moving and static parts of the pump are rusted, or the internal pressure of the pump is too high. If the pump disc is forced to start without moving the car, the strong motor force drives the pump shaft to rotate strongly, which will cause damage to the internal components, such as the pump shaft fracture, twist, impeller broken, motor coil burned, or the motor may trip and fail to start.
11. What is the role of oil sealing?
Cooling and sealing parts; lubricating friction; preventing damage by pumping out.
12. Why should the spare pump be cranked regularly?
The regular cranking has three functions: preventing the internal scale of the pump from getting stuck; preventing the pump shaft from deforming; the cranking can also bring the lubricating oil to the lubrication points to prevent the shaft from rusting, and the lubrication of the bearing is beneficial to immediately Drive.
16. What are the reasons for the abnormal heating of the centrifugal pump in operation?
Heat is a manifestation of the conversion of mechanical energy into heat energy. The common causes of abnormal heat generation of the pump are:
Heat with noise is usually caused by damage to the bearing ball cage.
The bearing stop sleeve in the bearing box is loose, and the front and rear glands are loose, causing heat due to friction.
The bearing hole is too large, causing the outer ring of the bearing to loosen.
There is a foreign body in the pump.
The rotor vibrates greatly, causing the seal ring to wear.
The pump is evacuated or the load on the pump is too high.
The rotor is unbalanced.
Too much or too little lubricating oil and substandard oil quality.
17. What are the reasons for the vibration of the centrifugal pump?
The rotor is unbalanced.
The pump shaft is misaligned with the motor, and the rubber ring on the wheel is aging.
Bearing or seal ring wears too much, resulting in rotor eccentricity.
The pump is evacuated or there is gas in the pump.
The suction pressure is too low, causing the liquid to vaporize or nearly vaporize.
The axial thrust becomes larger, causing stringing.
Improper lubrication of bearings and packings and excessive wear.
Worn or damaged bearings.
The impeller is partially blocked or the external auxiliary pipeline vibrates.
Too much or too little lubricating oil (grease).
The rigidity of the pump foundation is not enough, and the bolts are loose.
18. What are the vibration and bearing temperature standards for centrifugal pumps?
The vibration standards of centrifugal pumps are:
The speed is less than 1500vpm, and the vibration is less than 0.09mm.
The speed is 1500~3000vpm, and the vibration is less than 0.06mm.
The bearing temperature standards are: sliding bearings less than 65°C, rolling bearings less than 70°C.
19. When the pump is running normally, how much cooling water is suitable?
When the pump is working normally, the opening size of the cooling water is the most suitable when the drain temperature is about 40℃. At this time, touching the discharged water by hand has a little temperature, and the cooling effect is the best. In particular, the cooling water of the end face seal should not be opened too much in winter to prevent the sealing ring of the moving and static ring from being hardened due to the low water temperature, and losing the elasticity and causing the seal to fail.
20. What happens when the centrifugal pump is evacuated?
When the pump in operation starts to pump down, it will suddenly emit noise and vibration, accompanied by a decrease in pressure, flow, and current. When the evacuation is severe, the pump will vibrate strongly, the pressure will return to zero, and no liquid will flow out of the pump.
21. What are the reasons for the heating of the bearing box?
The pump shaft is not concentric with the motor shaft.
Too much lubricating oil (grease) or too little oil (grease) deteriorates.
The oil ring breaks or jumps out of the fixed position.
The axial thrust increases.
Insufficient or interrupted cooling water.
Bearing wear.
The flow is too small, making the pump nearly evacuated.
Pump vibration caused by weak foundation, unbalanced rotor, loose bolts, etc.
22. Why should the pump be antifreeze in winter?
The volume of water expands below zero. If the water left in the pump body is not cleaned out, the force generated by the volume expansion at low temperature will cause the pump body to burst and cause unnecessary damage. There are mainly the following methods to prevent freezing:
Drain the water in the idle pump.
Keep the cooling water flowing long and thin.
Insulate the pump or use steam or hot water to trace the heat.
The backup pump keeps the inlet and outlet flowing.
23. What should I do if the pump is frozen?
After the pump is frozen, it must not be directly blown with steam to prevent the pump from breaking due to uneven thermal expansion.
After the pump is frozen, pour it with cold water first, and then pour it with steam or hot water after turning the car.
24. Why should the pump body be cooled?
The flow friction between the liquid and the pump body during the operation of the pump, the rotating part and the fixed part, such as the ball of the bearing and the inner and outer rings, the shaft sleeve and the packing, will generate friction. The friction will generate heat, and the high temperature of the medium will be transferred to The machine pump heats the pump body. The purpose of cooling is to reduce the temperature of the pump body, pump seat, bearing box, and shaft seal to prevent deformation, aging and damage of these parts due to temperature rise.
25. Under what circumstances should the motor stop urgently?
When personal safety is endangered.
When the motor emits smoke, smells, or catches fire.
When there is a lot of vibration or axial movement.
When the body or bearing heats up to the limit.
The motor speed is slow with abnormal sound.
26. Explain the model of the domestically made centrifugal oil pump. For example, what does 100YⅡ-100×2A mean?
100--Pump suction port diameter Y--Single-stage centrifugal pump Ⅱ--Pump material code, the second type of carbon steel is not resistant to corrosion temperature 200～400℃ A--The first turning of the outer diameter of the impeller
27. How to distinguish cavitation phenomenon?
1. There is an intense noise in the pump.
2. The outlet pressure is unstable and can't hit the volume when it is severe.
3. The pump body vibrates.
4. The medium temperature rises
