Croos Pump (Shanghai) Co., Ltd.

Do you Know the 22 Basic Knowledge of Centrifugal Pumps?

The centrifugal pump is simple in structure, and it is easy to operate, and the flow is uniform, and it is easy to adjust and control, also it can be applied to a variety of special properties, so the centrifugal pump is the most commonly used liquid conveying machine in the chemical plant. In recent years, the centrifugal pump is developing towards the direction of large and high speed. The following is a list of 22 basic knowledge of centrifugal pumps, which I hope that it can help you.

1. The working principle of the centrifugal pump

The motor drives the impeller to rotate at high speed, and it will cause the liquid to produce centrifugal force. Because of the centrifugal force, the liquid is thrown into the side runner to discharge the pump, or enter the lower stage impeller, thus it will reduce the pressure of the impeller inlet. The pressure difference is formed with the pressure acting on the suction liquid, and the pressure difference acts on the liquid suction pump. As the centrifugal pump rotates constantly, the liquid is continuously sucked in or discharged.

2. The role of lubricating oil (fat)

Lubricating cooling, washing, sealing, reducing, protecting and unloading.

3. Which three levels of filtration are used before oil is used

Level 1: lubricating oil original barrel and fixed barrel;
Level 2: fixed oil drum and oil pot;
Level 3: between oil and gas.

4. The "five determination" of equipment lubrication

Fixed point: refueling at the specified point;
Timing: lubricate the lubrication area according to time and change oil regularly;
Quantitative: refueling by consumption;
Fixed quality: choose different lubricants according to different models, and maintain the quality of oil products;
Order: everyone must be responsible for each refueling site.

5. What is the harm of water in the lubricating oil of machine pump

Moisture can reduce the viscosity of lubricating oil, reduce the strength of oil film and reduce the lubrication effect.;  Water is lower than 0 ℃ to freeze, which seriously affect oil low temperature fluidity;                                              Water can accelerate the oxidation of lubricating oil and promote the corrosion of low molecular organic acids to  metals;

The water will increase the foam of the lubricating oil, making the lube prone to foam;                                              Water will rust the metal parts.

6. What are the maintenance contents of the machine pump

Conscientiously implement the post responsibility system and equipment maintenance and other regulations;
The lubrication of the equipment is "fixed" and "three-level filtration", and the lubrication device is complete and clean;
Maintenance tools, safety facilities, fire fighting equipment and other complete intact, put in neat.

7.The standard for leakage of common shaft seals

Packing seal: light oil less than 20 drops/minute heavy oil less than 10 drops/min;
Mechanical seal: light oil less than 10 drops/minute heavy oil less than 5 drops/min.

8. Why can't the centrifugal pump start when it is not moving

The centrifugal pump does not move the car, which indicating the internal failure of the pump, the fault may be that the impeller is stuck or the pump shaft is bent over, or the pump is moving, the static part of the rust dies, or the pressure in the pump is too high. If the pump disk does not move the car and forced to start, powerful motor power to drive the pump shaft strong action, it will cause damage to the internal parts, such as the pump shaft fracture, distortion, impeller, motor coil burned, it also may make the trip, start-up failure.

9. What is the function of sealing oil

Cooling sealing parts; Lubrication friction payment; Prevent the damage from vacuuming.

10. Why do it need a spare pump regularly

Regular turning have three functions:
Prevent the pump from getting stuck; Prevent pump shaft deformation; The car can also take the lube to the lubrication points, prevent the shaft rusting, and the bearings are lubricated to facilitate the driving in a state of emergency.

11. Causes of abnormal heating of centrifugal pumps in operation

Heating is the performance of mechanical energy conversion to heat energy.                                                          With the heat of noise, it is usually the bearing ball separation frame damaged;
The bearing in the bearing box is loose, the front and rear pressure is loose, and the friction causes fever;
The bearing hole is too large to cause the bearing outer ring loose;
There is foreign body in the pump;
The rotor vibration is large to cause the sealing ring to wear;
Pump suction or pump load is too large;
Rotor imbalance;
Too much oil or too little oil and not qualified.

12. The causes of centrifugal pump vibration

Rotor imbalance;
The pump shaft and the motor are not in the middle, the wheel rubber ring aging;
The bearing or sealing ring is worn too much to form a rotor eccentric.
Pump air or pump gas;
The suction pressure is too low to make the liquid vaporize or close to vaporization;
The axial thrust becomes larger, causing the string axis;
Improper lubrication of bearing and packing;
Bearing wear or damage;
The vibration of the impeller partial plug or external subsidiary pipeline;
Lubricating oil (fat) too much or too little;
The foundation stiffness of machine pump is not enough, the bolt is loose.

13. The standard of centrifugal pump vibration and bearing temperature

The vibration standard of centrifugal pump:
The speed is less than 1500 vpm and the vibration is less than 0.09 mm.
Rotating speed 1500 ~ 3000 vpm, vibration is less than 0.06 mm.
The standard for the bearing temperature: sliding bearing is less than 65 ℃, the rolling bearing is less than 70 ℃.

14. When the pump is running properly, how much is the cooling water?

When the pump is in normal operation, the cooling water should be opened at a temperature of about 40 DEG C, which is most suitable. At this time, the hand contact with the discharge of the water is a bit of temperature, the cooling effect is the best. In particular, the cooling water of the end seal cannot be opened too much in winter to prevent the sealing ring of the static ring from being hardened by the low water temperature.

15. What is the phenomenon of centrifugal pump

When the pump in operation begins to take time out, it will suddenly make noise and vibration, with the decrease of pressure, flow and current. When the pump is serious, the pump will vibrate strongly and the pressure will return to zero.

16. The causes of bearing box heating

The pump shaft is different from the motor shaft;
Oil (fat) too much or too little, oil (fat) deterioration;
Break with oil ring or jump out of position;
Axial thrust increases;
The cooling water is insufficient or interrupted;
Bearing wear;
The flow is too small to make the pump close to the pumping state;
The foundation is not stable, the rotor is unbalanced, the bolt loosens and so on causes the machine pump vibration;

17. Why is the pump anti-freeze in winter

If the water in the pump is not cleaned out, the power of the expansion of the volume at low temperature will cause the pump to burst, causing unnecessary damage. There are several methods for anti-freezing:

Drain the water in the idle pump;

Keep the cooling water flowing;
Heat the pump with steam or hot water;
The spare pump is kept in circulation.

18. How do you handle the pump after it's frozen

After the pump has been frozen, it can not be blown directly by steam, in case the pump body is not evenly split;
When the pump is frozen, water the pump with cold water, then the car can be filled with steam or hot water.

19. Why is the pump cooling

The flow friction generated by the pump in the running liquid and the pump body, the rotational part and the fixed part, such as the ball bearing of the bearing and the inner and outer ring, the shaft sleeve and the packing, will produce friction, because the friction will produce heat. Due to the high medium temperature conduction to pump at the same time, it will make the pump body heat, and the purpose of the cooling is to reduce the pump body, pump seat, bearing housing and shaft sealing temperature, to prevent these parts deformation, aging and damage due to temperature rise.

20. When is the motor to stop

When personal safety is endangered;
When the motor smokes or smells or catches fire;
When a large vibration or axial sequence occurs;
When the fuselage or bearing heats to the limit;
Motor speed is slow with abnormal sound.

21. Explain the model of domestic centrifugal oil pump

100 -- pump suction inlet diameter, Y -- single-stage centrifugal pump, Ⅱ - pump with material code, the second kind of carbon steel is not corrosion resistant temperature 200 ~ 400 ℃, A -- the first turning of the outer diameter of the impeller.

22. How to check the cavitation phenomenon

The pump has loud noise;
The export pressure is not stable, and the serious time can not be measured;
Pump body vibration;
The temperature of the medium goes up.

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