Multistage Pump: Definition&Structure&Features&Maintenance
The multistage pump is a centrifugal pump that combines the inlet and outlet sections and the middle section through a tie rod. Its output water pressure can be very large, and it also relies on the rotation of the impeller to obtain centrifugal force to obtain materials. When the gas density reaches the working range of the mechanical vacuum pump, it is pumped out, thereby gradually obtaining a high vacuum.
The multistage pump relies on the change of pump cavity volume to achieve suction, compression and exhaust, so it is a centrifugal pump with variable volume.
Table of Contents
2 Features
3 Parameters
4 Maintenance
5 Classification
6 Working Principle
7 Common faults
8 Installation and use
9 Structure diagram
10 Other related
1 Structure description
The basic structure of a multistage pump is composed of inlet section, outlet section, middle section, tail cover, impeller, pump body, pump shaft, bearing, sealing ring, stuffing box and other components.
1. The impeller is the core part of the multistagepump. It has a high speed and a large output. The blades on the impeller play a major role. The impeller must pass a static balance experiment before assembly. The inner and outer surfaces of the impeller are required to be smooth to reduce the friction loss of the water flow.
2. The inlet section, outlet section and middle section are also called pump casings, which are the main body of the multistagepump. Play a supporting and fixing role, and connect with the bracket for mounting the bearing.
3. The function of the pump shaft is to connect the motor with the coupling, and transmit the torque of the motor to the impeller, so it is the main component that transmits mechanical energy.
4. The bearing is a component that is sleeved on the pump shaft to support the pump shaft. There are two types of rolling bearings and sliding bearings. Rolling bearings use tallow as a lubricant to refuel properly. Generally 2/3～3/4 of the volume is too much to generate heat, too little and there is noise and heat! The sliding bearing uses transparent oil as lubricant, add oil to the oil level line. Too much oil will seep out along the pump shaft and drift low, and too little bearing will overheat and burn out causing accidents! During the operation of the pump, the temperature of the bearing is up to 85 degrees and generally runs at about 60 degrees. If it is high, find out the cause (whether there are impurities, whether the oil is black, whether water has entered) and deal with it in time!
5. The sealing ring is also called the leakage reducing ring. The gap between the impeller inlet and the pump casing is too large to cause the water in the high-pressure area of the pump to flow to the low-pressure area through this gap, affecting the pump's water output and reducing efficiency! If the clearance is too small, friction between the impeller and the pump casing will cause wear. In order to increase the reflux resistance, reduce internal leakage, and delay the service life of the impeller and the pump casing, a sealing ring is installed at the junction of the inner edge of the pump casing and the external aid of the impeller, and the sealing gap should be kept between 0.25 and 1.10 mm.
6. The stuffing box is mainly composed of packing, water seal ring, packing tube, packing gland and water seal pipe. The function of the stuffing box is mainly to close the gap between the pump casing and the pump shaft, so that the water in the pump does not flow to the outside and the outside air does not enter the pump. Always maintain the vacuum in the pump! When the pump shaft and the packing friction generate heat, the water seal pipes the water into the water seal ring to cool the packing! Maintain the normal operation of the pump. Therefore, special attention should be paid to the inspection of the stuffing box during the itinerant inspection of the pump operation! The packing should be replaced after 600 hours of operation.
7. Suction and dischargecan be changed of multistage pump.
2 Features
Multistage pump refers to a pump with two or more impellers.
3 Parameters
Flow rate: 6.3~450 cubic meters per hour
75~685 meters
Motor power: 5.5~1050kw
Product standard: JB/T1051-93
4 Maintenance
⑴. check the multistage pump pipeline and joints for looseness. Turn the multistage pump by hand to see if the multistage pump is flexible.
⑵. Add bearing lubricating oil to the bearing body, observe that the oil level should be at the center line of the oil mark, and the lubricating oil should be replaced or replenished in time.
⑶. Unscrew the water diversion screw plug of the pump body of the multistage pump, and pour water diversion (or slurry).
⑷. Close the gate valve, outlet pressure gauge and inlet vacuum gauge of the water outlet pipeline.
⑸. Jog the motor to see if the rotation direction of the motor is correct.
⑹. If the multistage pump is out of service for a long time, it is necessary to disassemble all the pumps, wipe off the water, and coat the rotating parts and joints with grease and install them.
⑺. Try to control the flow and head of the multistage pump within the range indicated on the label to ensure that the multistage pump runs at the highest efficiency point in order to obtain the greatest energy saving effect.
⑻. During the operation of the multistage pump, the bearing temperature should not exceed the ambient temperature of 35C, and the maximum temperature should not exceed 80C.
⑼. If abnormal sound is found in the multistage pump, stop and check the cause immediately.
⑽. When the multistage pump wants to stop using, first close the gate valve and pressure gauge, and then stop the motor.
⑾. During the first month of operation, the multistage pump should change the lubricating oil after 100 hours, and then change the oil once every 500 hours.
⑿. multistage pumps frequently adjust the packing gland to ensure normal dripping in the packing chamber (it is better to leak out as drips).
⒀. Regularly check the wear of the shaft sleeve of the multistage pump, and replace it in time when the wear is large.
⒁. When the multistage pump is used in the cold winter, after stopping, unscrew the water drain plug at the bottom of the pump body to drain the medium. Prevent freezing and cracking.
⒂. Turn on the motor. When the multistage pump runs normally, turn on the outlet pressure gauge and the inlet vacuum pump, and then gradually open the gate valve and check the motor load.
5 Categories
There are many series of multistage pumps, which are divided into vertical multistage pumps and horizontal multistage pumps according to their appearance.
According to different materials, it can be divided into: stainless steel multistage pump, LG type multistage pump, D type multistage pump.
The difference between multistage and single-stage pump
1. Multistagepump refers to a pump with two or more impellers, the highest head can exceed 125 meters.
2. A single-stage pump refers to a pump with only one impeller, with a maximum head of only 125 meters.
LG type multistage pump, DL vertical multistage pump, D type multistage pump, MD type multistage pump, multistage pump series
6 Working principle
multistage pump is a kind of centrifugal pump, and it also relies on the rotation of the impeller to obtain centrifugal force and thus material. When the gas density reaches the working range of the mechanical vacuum pump, it is pumped out, thereby gradually obtaining a high vacuum.
multistage pumps can be used in many industrial sectors such as petroleum, chemical, machinery, mining, light industry, medicine and food. In many processes of industrial production, such as vacuum filtration, vacuum water diversion, vacuum feeding, vacuum evaporation, vacuum concentration, vacuum rehydration and vacuum degassing, multistage pumps are widely used. It can pump out flammable and explosive gas, and also can pump out dusty and water-containing gas. Therefore, the application of water ring pumps is increasing.
7 Common faults
Fault one
The pump does not absorb water, the pointer of the pressure gauge and the vacuum gauge jumps violently
the reason:
Solution:
Fault two
The pump does not absorb water, the vacuum gauge indicates high vacuum
Reasons: 1. The bottom valve is not opened or has been blocked 2. The resistance of the suction pipe is too large 3. The filter is blocked
Solution: 1. Check the bottom valve 2. Replace the suction 3. Clean the filter
Fault three
The pressure gauge is under pressure but still no water
Reasons: 1. The resistance of the outlet pipe is too large 2. The direction of rotation is wrong 3. The valve of the outlet pipe is not opened 4. The impeller is blocked
Solution: 1. Check or shorten the water pipe 2. Check the motor. Adjust the two to each other 3. Open the outlet valve 4. Remove the dirt from the impeller
Fault four
Not reach design flow
Reasons: 1. There is air inhalation 2. Due to the lowering of the water level, the submerging depth is not enough 3. The impeller is blocked by foreign matter 4. The rotor part is severely worn
Solution: 1. Check the leaking part and remove it. 2. Extend the suction pipe. Deepen the depth of flooding. 3. Remove and drop the foreign matter. 4. Replace the sealing ring.
Fault five
Pump consumes too much power
Reasons: 1. The packing is too tight and heats up 2. The flow is too large 3. There is friction between the rotating body and the shell 4. The pump bearing is worn out 5. The pump shaft is bent
Solution: 1. Properly relax the packing pressure 2. Close the opening of the small gate valve 3. Adjust the position of the rotating body and the housing 4. Replace the bearing 5. Replace or correct
Fault six
Increased pump vibration
Reasons: 1. The impeller is partially blocked 2. The impeller is damaged 3. The flow rate is too small 4. The pump shaft is not concentric with the motor 5. The bearing is damaged 6. Air is mixed in. Cavitation occurs
Solution: 1. Disassemble and remove foreign matter 2. Replace the impeller 3. Slightly open the outlet valve 4. Align at a fixed point 5. Change the suction position. Improve the suction pipe
8 Installation and use
Installation
In addition to meeting the general technical requirements for installation, the following points should be noted when installing this type of pump:
1. When the motor and water pump are combined and installed, the shaft of the coupling end of the pump should be pulled out, and the end face clearance value of 3-5mm should be left to ensure the axial clearance value between the pump and the motor coupling.
Note: Make sure the bottom plate is leveled and the equipment level is good before grouting
Caution: In order for the installation to be successful, the coupling must be adjusted correctly. The flexible coupling cannot compensate for any obvious misalignment. Misalignment can cause rapid wear, noise, vibration, and damage to equipment. Therefore, the coupling must be adjusted within the given limits.
Caution: Measures must be taken to support the inlet and outlet pipes of the pump to prevent excessive load on the inlet and outlet of the pump
2. The center lines of the pump and motor shafts should be on the same horizontal straight line.
3. The pump can only bear its own internal force and cannot bear any external force.
Start, run, stop
(1) Starting:
Warning: For the safety of the operator, do not operate beyond the conditions on the pump nameplate, so as not to endanger the safety of the equipment and operators. To ensure the smooth operation and maintenance of the pump and other actions, please refer to the manual.
1. Before starting the pump, the rotor should be turned to check whether the rotor is flexible.
2. Check whether the rotation of the motor is consistent with the rotation of the pump.
3. Close the pump outlet gate valve and pressure gauge cock, and use the conveyed liquid or vacuum system to remove the air in the suction pipe and the pump body (it is strictly forbidden to start operation when empty).
4. Check the tightness of the connecting bolts between the pump and the motor and the safety conditions around the pump, so that the pump is ready to start.
Warning: The equipment can only be operated after the coupling guard is installed. Ignoring this point may cause casualties.
5. Start the pump. After the pump runs normally, open the pressure gauge cock, slowly open the outlet gate valve, and control the given head of the pump according to the reading of the outlet pressure gauge.
(2) Operation:
1. This type of pump relies on the internal balance mechanism to balance the axial force. The balance device has a balance liquid flowing out, and the balance liquid is connected to the suction section by the balance water pipe.
2. The rolling bearings of this pump are equipped with cooling devices, and the cooling water pipe must be connected before the pump runs. The change in bearing temperature rise reflects the assembly quality of the pump. The bearing temperature rise should not be higher than the ambient temperature 35°C, and the maximum temperature should not be higher than 75°C.
Warning: Operation of equipment that is not properly lubricated may cause bearing heating, breakage, pump blockage, equipment damage, and personal injury to the operator.
3. The rotor of this type of pump has a certain amount of axial movement during operation, and the gap value between the end faces of the motor and the water pump should be guaranteed.
4. During the operation of the pump, the wear of the impeller, sealing ring, guide vane sleeve, balance disc, and shaft sleeve should be checked regularly. If the wear is too large, it should be replaced in time.
Warning: Do not try to repair, maintain or clean up near rotating machinery, otherwise it will endanger the personal safety of operators.
5. The user should work out more detailed operating procedures according to the specific situation.
(3) Stop: Before stopping, turn off the pressure gauge cock, then slowly close the outlet gate valve, and stop the motor after the outlet gate valve is closed.
9 Structure diagram
10 Other related
The multistage pump adopts computer design and optimization processing. The company has strong technical force, rich production experience and perfect testing methods to ensure the stable and reliable product quality. multistage pump, horizontal, single-suction multistage, segmented centrifugal pump. It has the characteristics of high efficiency, wide performance range, safe and stable operation, low noise, long life, and convenient installation and maintenance. For transporting clean water or other liquids with physical and chemical properties similar to water. It can also be used to transport hot water, oil, corrosive or abrasive media by changing the material and sealing form of the pump's flow-through components and adding a cooling system. The product implements the standard of JB/T1051-93 "multistage clean water centrifugal pump type and basic parameters".
Structure description
The multistage pump is mainly composed of four parts: stator, rotor, bearing and shaft seal:
1. The stator part of the multistagepump is mainly composed of the suction section, the middle section, the discharge section and the guide vane. There are tension bolts to clamp each section to form a working room. The D-type pump generally sucks in horizontally and discharges vertically upwards; when it is used for oilfield water injection, the inlet and outlet of the pump are vertically upward. The outlet and inlet of the DG multistagepump are vertically upward.
2. The rotor part of the multistagepump is mainly composed of shaft, impeller, balance disc and shaft sleeve. The axial force is balanced by the balance plate.
3. Multistagepump bearings are mainly composed of bearing bodies, bearings and bearing glands. The bearings are lubricated with grease or thin oil.
4. The shaft seal of the multistagepump adopts soft packing seal, which is mainly composed of the sealing box body, packing and water retaining ring on the water inlet section and the tail cover. D type pump seal water comes from the pressure water in the pump. The sealing water of DG pump comes from external water supply.
5. Multistage pump rotation. The pump is directly driven by the prime mover through an elastic coupling. Looking at the pump from the prime mover side, the pump rotates clockwise. D and DG pumps are horizontal single-suction multistagecentrifugal pumps. For transporting clean water (with impurities less than 1%, particle size less than 0.1mm) or other liquids with physical and chemical properties similar to water. The medium temperature of D-type pump is less than 100℃, suitable for mine drainage, oil field water injection, factory and urban water supply and drainage. Oil field water injection pumps use different materials according to the corrosiveness of the medium. The medium temperature of the DG pump is less than 120℃, which is suitable for various boiler feed water.
The difference between other pumps
1. Single-stage pump refers to a pump with only one impeller, and the maximum head is only 125 meters;
2. Multistagepump refers to a pump with two or more impellers, the highest head can reach 1000 meters;
3. When the actual pump head is less than 125 meters, you can consider whether to choose a single-stage pump or a multistagepump according to the pump room area, pump price (multistagepumps are generally higher than single-stage pumps), and other factors. With the advancement of technology, single-stage impeller pumps can increase the pump head by increasing the pump speed, which can replace multistage pumps, but the price is a bit more expensive.
Precautions
Pumps should be divided into electrical and mechanical aspects. For the mechanical aspect, you can find out by comparing the previous maintenance records. The second is the electrical aspect. It is necessary to understand the power of each pump motor and have a certain understanding of its control system.
