Mar 06, 2021
Centrifugal pump is simple in structure, easy to operate, uniform flow, convenient to adjust and control, and can be used for a variety of special materials. Therefore, centrifugal pump is the most commonly used liquid conveying machine in chemical plants. In recent years, centrifugal pump is developing in the direction of large scale and high speed. Below, the small edition has sorted out 22 basic knowledge of centrifugal pump for you, hoping to help you
Working principle of centrifugal pump
The motor drives the impeller to rotate at high speed, which causes the liquid to produce centrifugal force. Due to the centrifugal force, the liquid is dumped outside the side channel to discharge the pump or into the next impeller, so that the pressure at the inlet of the impeller is reduced, and the pressure difference is formed with the pressure acting on the liquid. The differential pressure acts on the liquid suction pump. Because of the continuous rotation of the centrifugal pump, the liquid is continuously inhaled or drawn in Discharge.
The function of lubricating oil (grease)
Lubrication cooling, flushing, sealing, vibration reduction, protection and unloading.
Which three stages of filtration should the lubricating oil pass before use
First stage: between original and fixed drum of lubricating oil;
Second stage: fixed between oil drum and oil pot;
Level 3: between the oil pot and the filling point.
"Five determinations" of equipment lubrication
Fixed point: refuel according to the specified point;
Timing: fill lubricating parts according to specified time and change oil regularly;
Quantitative: fuel according to consumption;
Quality determination: choose different lubricating oil according to different models and keep the oil quality qualified;
Fixed person: each refueling part must be responsible by a special person.
What harm is the water content in the lubricating oil of the pump
1. Water can reduce the viscosity of lubricating oil, reduce the strength of oil film and reduce the lubrication effect.
2. Water below 0 ℃ will freeze, which seriously affects the low temperature fluidity of lubricating oil.
3. Water can accelerate the oxidation of lubricating oil and promote the corrosion of low molecular organic acids on metals.
4, moisture will increase the foaming property of lubricating oil and make the lubricant easy to produce foam.
5. Moisture can rust metal parts.
What are the maintenance contents of the pump
1. Conscientiously implement post responsibility system and equipment maintenance rules and regulations.
2. The equipment lubrication shall be "five fixed" and "three-stage filtration", and the lubricating instruments shall be complete and clean.
3. Maintenance tools, safety facilities, fire fighting equipment, etc. are complete and in good condition, and are placed in a complete and complete manner.
Standard for common shaft seal leakage
Packing seal: light oil less than 20 drops / minute heavy oil less than 10 drops / minute
Mechanical seal: light oil less than 10 drops / minute heavy oil less than 5 drops / min
Why can't the centrifugal pump disk start when it is not running
If the centrifugal pump plate is not motor car, it means that there is a failure in the pump. This failure may be caused by the impeller being stuck or the pump shaft is bent excessively, or the dynamic and static parts of the pump rust or the pressure inside the pump is too high. If the pump disc is not forced to start without motor, strong motor force will drive the pump shaft to move strongly, which will cause damage to internal parts, such as pump shaft fracture, twist, impeller breakage, motor coil burning, and motor tripping and failure of start-up.
What is the function of oil sealing
1. Cooling the sealing parts;
2. Lubrication friction payment;
3. Prevent the damage of evacuation.
Why do standby pumps crank regularly
There are three functions of regular turning:
1. Prevent the pump from sticking with scale;
2. Prevent the deformation of pump shaft;
3. Turning can also take lubricating oil to all lubrication points to prevent shaft rust. Bearing lubrication is conducive to driving in emergency.
The cause of abnormal heating of centrifugal pump in operation
The heat is the performance of mechanical energy transformation into heat energy, and the common causes of abnormal heat of the pump are as follows:
1. The heat with noise is usually damaged by the bearing ball insulator;
2. The bearing sleeve in the bearing box is loose, the front and rear gland are loose, and the heat is caused by friction;
3. Too large bearing hole causes loose outer ring of bearing;
4. Foreign body of pump;
5. The rotor vibration is large, so that the sealing ring is worn;
6. Pump is empty or the pump load is too large;
7. Rotor unbalance;
8. Too much or too little lubricating oil and unqualified oil quality.
The reason of centrifugal pump vibration
1. Rotor unbalance;
2. The pump shaft is not in alignment with the motor, and the rubber ring of the wheel is aged;
3. The bearing or sealing ring is worn too much, which causes the rotor to be eccentric;
4. Pump is empty or there is gas in the pump;
5. The suction pressure is too low to vaporize or close to vaporization of the liquid;
6. The axial thrust becomes larger, causing the series of shafts;
7. Improper lubrication of bearings and packing, excessive wear;
8. Bearing wear or damage;
9. Impeller is partially blocked or external auxiliary pipeline vibrates;
10. Too much or too little lubricating oil (grease);
11. The foundation rigidity of the pump is not enough and the bolts are loose.
Standard for vibration and bearing temperature of centrifugal pump
The vibration standard of centrifugal pump is: 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 temperature standard of bearing is: the sliding bearing is less than 65 ℃, and the rolling bearing is less than 70 ℃.
How much cooling water is suitable for normal operation of the pump
When the pump is in normal operation, the opening size of cooling water is about 40 ℃ and the most suitable. At this time, the temperature of the water discharged by hand is a little bit, and the cooling effect is the best. Especially, the cooling water of end seal cannot be opened too much in winter to prevent the sealing ring of dynamic and static ring hardening due to low water temperature and failure of elasticity.
What happens when the centrifugal pump is empty
When the pump starts to empty, it will suddenly generate noise and vibration, and it will be accompanied by pressure, flow reduction and current reduction. When the pump is vacuumized seriously, the pump will vibrate strongly, the pressure will return to zero, and there is no liquid in the pump.
The reason of bearing box heating
1. The pump shaft is not concentric with the motor shaft.
2. Too much or too little lubricating oil (grease) is deteriorated.
3. Broken or jumping out of fixed position with oil ring.
4. The axial thrust increases.
5. Insufficient or interrupted cooling water.
6. The bearings are worn.
7. The flow rate is too small to make the pump close to the pumping state.
8. The vibration of the pump caused by the foundation is not firm, the rotor is unbalanced, and the bolts are loose.
Why should pump freeze in winter
If the water left in the pump body is not cleaned out, the force of volume expansion under low temperature will cause the pump body to expand and crack, causing unnecessary damage. The methods of antifreeze are as follows:
1. Drain the water in the idle pump.
2. Keep the cooling water flowing in fine water.
3. Heat preservation or tracing with steam and hot water for the pump.
4. The standby pump keeps the inlet and outlet flowing.
How to deal with the pump after freezing
1. After the pump is frozen, it is never allowed to blow directly with steam to prevent the pump body from cracking due to uneven thermal expansion.
2. After the pump is frozen, it is poured with cold water, and then it can be poured with steam or hot water.
Why should the pump body cool down
The flow friction between the liquid and the pump body during the operation of the pump, friction will occur between the rotating part and the fixed part such as the ball and inner and outer rings of the bearing, the sleeve and the packing part of the bearing. The heat will be generated due to friction. At the same time, the high medium temperature will transmit to the pump, which makes the pump body heat. The purpose of cooling is to reduce the temperature of the pump body, pump seat, bearing box and shaft seal, so as to prevent the temperature rise of these parts due to temperature rise And deformation, aging and damage.
Under what circumstances the motor needs to stop urgently
1. When endangering personal safety;
2. When the motor is smoking or smelling or starting fire;
3. When there is a great vibration or axial series motion;
4. When the body or bearing is heated to the limit;
5. The motor speed is slow and abnormal sound is accompanied.
Explain the model of domestic centrifugal oil pump
100 - diameter of pump suction port
Y -- single stage centrifugal pump
Ⅱ -- material code for pump, corrosion resistance temperature of the second carbon steel is 200-400 ℃
A -- the first turning of impeller outer diameter
How to distinguish cavitation phenomenon
1. There is a strong noise in the pump;
2. The outlet pressure is unstable and cannot be hit when it is serious;
3. Pump body vibration;
4. The medium temperature increases.