Centrifugal pump

Structure and composition

        The basic structure of the centrifugal pump is composed of six parts: impeller, pump body, pump shaft, bearing, sealing ring and stuffing box.

        1. The impeller is the core part of the centrifugal pump. Its high speed is high, and the blades on the impeller play a major role. The impeller must pass the static balance test before assembly. The inner and outer surfaces of the impeller are required to be smooth to reduce the frictional loss of water flow.

        2, the pump body is also called the pump casing, it is the main body of the pump. It acts as a support and is attached to the bracket on which the bearing is mounted.

        3. The function of the pump shaft is to connect the coupling to the motor and transmit the torque of the motor to the impeller, so it is the main component that transmits mechanical energy.

        4, the sliding bearing uses a transparent oil as a lubricant, refueling to the oil line. Too much oil will seep out along the pump shaft, too few bearings will overheat and burn out! During the operation of the pump, the temperature of the bearing is up to 85 degrees, and it is generally running at about 60 degrees.

        5, the seal ring is also known as the leak reduction ring.

        6. The stuffing box is mainly composed of packing, water sealing ring, packing tube, packing gland and water sealing tube. 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 keep the vacuum inside the pump! When the pump shaft and the packing friction generate heat, the water seals the water to the water seal ring to cool the packing! Keep the pump running properly. Therefore, it is especially important to check the stuffing box during the running inspection of the pump! The packing should be replaced after about 600 hours of operation.

        product analysis

        Basic structure

        The basic structure of the centrifugal pump is composed of eight parts: impeller, pump body, pump cover, water retaining ring, pump shaft, bearing, sealing ring, stuffing box, axial force balance device.

        1. The impeller is the core part of the centrifugal pump, and its output speed is high.

        2. The pump body is also called the pump casing, which is the main body of the pump. It acts as a support and is attached to the bracket on which the bearing is mounted.

        3. The function of the pump shaft is to connect the coupling to the motor and transmit the torque of the motor to the impeller, so it is the main component that transmits mechanical energy.

        4. The sealing ring is also called the leak reducing ring.

        5. The stuffing box is mainly made of packing, so that the water in the pump does not flow to the outside and the outside air does not enter the pump. Always keep the vacuum inside the pump! When the pump shaft and the packing friction generate heat, the water seal pipe is injected into the water seal ring to cool the packing!

        6. The axial force balance device, during the operation of the centrifugal pump, because the liquid enters the impeller at a low pressure and flows out under high pressure, the pressure on both sides of the impeller is unequal, and an axial thrust directed to the inlet direction is generated. It will cause axial turbulence of the rotor, resulting in wear and vibration. Therefore, an axial thrust bearing should be provided to balance the axial force.

        kind

        First, according to the number of impellers

        1. Single-stage pump: there is only one impeller on the pump shaft.

        2. Multi-stage pump: There are two or more impellers on the pump shaft. At this time, the total lift of the pump is the sum of the lifts generated by n impellers.

        Multistage centrifugal pump

        Second, according to work pressure to classify

        1. Low pressure pump: the pressure is less than 100 meters water column;

        2. Medium pressure pump: the pressure is between 100~650 meters of water column;

        3. High pressure pump: The pressure is higher than 650 meters water column.

        Third, according to the impeller suction method

        1. Single-side water inlet pump: also called single suction pump, that is, there is only one water inlet on the impeller;

        2, double-side inlet pump: also called double suction pump, that is, there is a water inlet on both sides of the impeller. It has twice the flow rate of a single-suction pump and can be approximated as two single-suction pump impellers placed back to back together.

        Fourth, according to the combination of pump casing

        1. Horizontal open-type pump: that is, a joint seam is formed on the horizontal plane passing through the axial line.

        2. Vertical joint surface pump: the joint surface is perpendicular to the axis of the shaft.

        Fifth, according to the position of the pump shaft

        1. Horizontal pump: The pump shaft is in a horizontal position.

        Horizontal pump

        2. Vertical pump: The pump shaft is in a vertical position.

        6. Classification according to the way of impeller

        1. Volute pump: After the water comes out of the impeller, it directly enters the pump casing with a spiral shape.

        2. Vane pump: After the water comes out of the impeller, it enters the guide vane set outside it, and then enters the next stage or flows into the outlet pipe.

        Seven, according to the installation height classification

        1. Self-priming centrifugal pump: The pump shaft is lower than the pool surface of the sink. It does not need to be filled when starting, and can be started automatically.

        2. Suction centrifugal pump (non-self-priming centrifugal pump): The pump shaft is higher than the suction pool surface. Before starting, it is necessary to fill the pump casing and the suction pipe with water first, then drive the motor to make the impeller rotate at a high speed. The water is pulled out of the impeller by the centrifugal force, and the center of the impeller forms a negative pressure. The water in the suction pool enters the impeller under the action of atmospheric pressure. It is also subjected to a high-speed rotating impeller and is pulled out of the impeller into the pressurized water pipe.

        In addition, classification can also be carried out according to the application, such as oil pump, water pump, condensate pump, ash pump, circulating water pump, and the like.

        Characteristics

        By inhalation

        Single suction pump liquid flows into the impeller from one side, there is axial force

        The double suction pump liquid flows into the impeller from both sides, there is no axial force, and the pump flow rate is almost double that of the single suction pump.

        By number of stages

        There is only one impeller on the shaft of the single-stage pump

        The multi-stage pump is equipped with two or more impellers on the same pump shaft, and the liquid flows through each stage of the impeller in turn. The more the number of stages, the higher the lift.

        Pump axis orientation

        Horizontal pump shaft horizontal placement

        Vertical pump shaft perpendicular to the horizontal plane

        By housing type

        The segmented pump housing is in a flat portion perpendicular to the shaft, and the segments are connected to the segments by long bolts.

        The split-open pump housing is split in a plane passing through the axis of the shaft

        The volute pump is equipped with a centrifugal pump with a spiral pressurized water chamber, such as a commonly used end suction cantilever centrifugal pump.

        Turbine pump with a vane-type pressurized water chamber

        Special structure

        The pipeline pump is part of the pipeline and does not need to be changed during installation.

        Submersible pump and electric motor are integrated into the water

        The submerged pump body is immersed in the liquid

        The shield pump impeller is integrated with the motor rotor and is in the same sealed housing. It does not need to adopt a sealing structure and belongs to a leak-free pump.

        In addition to the inlet and outlet of the magnetic pump, the pump body is completely closed, and the connection between the pump and the motor is driven by magnetic steel mutual suction.

        Self-priming pump, no need to fill the pump when starting

        The high-speed pump increases the speed of the pump shaft by the speed increasing box. The general speed can reach more than 10000r/min. It can also be called partial flow pump or tangential booster pump.

        The inlet and outlet of the vertical cylinder pump are at the same height at the upper part. There are two inner and outer shells. The inner shell is composed of a rotor and a vane. The outer shell is an inlet guide passage, and the liquid is sucked from the lower part.

        ISG life water pump, living pump, community water pump, living water supply and drainage equipment, according to IS, IR type centrifugal pump performance parameters and vertical pump unique structural combination design, and strictly in accordance with ISO2858 requirements for design and manufacture, using domestic high quality hydraulic model Designed to be the ideal new generation of horizontal pump products. This product is always made of cemented carbide mechanical seal. Applications: ISW pumps are suitable for industrial and urban water supply and drainage, such as high-rise building pressurized water supply, garden sprinkler irrigation, fire booster, long-distance transportation, HVAC refrigeration cycle, bathroom and other pressurization and equipment, the use temperature does not exceed 85 °C. ISWR pumps are widely used in: boiler heat source water pressurization, transportation, and urban heating systems in metallurgy, chemical, textile, paper, and restaurant. The SGWR type temperature does not exceed 120 °C.

        use

        The test run of the pump should meet the following requirements:

        1 The steering of the drive should be the same as the steering of the pump;

        2 to identify the steering of the pipeline pump and the coaxial pump;

        3 The fixed joints should be free from looseness. The specifications and quantity of lubricants for each lubrication part should meet the requirements of the equipment technical documents;

        4 The parts with pre-lubrication requirements shall be pre-lubricated as required;

        5 All indicating instruments and safety protection devices should be sensitive, accurate and reliable;

        6-disc should be flexible and free of abnormalities;

        7 The high temperature pump should be preheated before the test run, the temperature should rise evenly, the temperature rise per hour should not exceed 50 °C; the temperature difference between the surface of the pump body and the process pipe with the working medium inlet should not exceed 40 °C;

        8 Set the connection device to eliminate the influence of temperature rise, and set the bypass connection device to provide cooling water source.

        Pay attention to the following points when operating the centrifugal pump:

        1 It is forbidden to run without water, do not adjust the suction port to reduce the displacement, and prohibit running under too low flow rate;

        2 Monitor the operation process, completely prevent the stuffing box from leaking, and use new packing when replacing the stuffing box;

        3 to ensure that the mechanical seal has a fully flushed water flow, water-cooled bearings are prohibited from using excessive water flow;

        4 Do not use too much lubricant;

        5 Check according to the recommended cycle. Establish operational records including hours of operation, adjustment and replacement of packing, addition of lubricants and other maintenance measures and time. Pumping and discharge pressures, flow rates, input power, wash and bearing temperatures, and vibration conditions should be measured periodically.

        6 The main engine of the centrifugal pump relies on atmospheric pressure to pump the low water to a high place, and the atmospheric pressure can only support the water column of about 10.3m at most, so the main engine of the centrifugal pump can not work 12 meters away from the water surface.

        maintain

        3.1. Analysis of failure of mechanical seal of centrifugal pump

        Centrifugal pump shutdown is mainly caused by the failure of the mechanical seal. Most of the failures are leaks. The reasons for the leaks are as follows:

        1 Leakage of the static sealing surface of the static ring, the main reasons are: the flatness of the end face, the roughness does not meet the requirements, or the surface is scratched; there are particulate matter between the end faces, so that the two ends can not run the same; the installation is not in place, the way is not correct.

        2 compensation ring seal leakage, the main reasons are: gland deformation, pre-tightening force is uneven; installation is not correct; the quality of the seal ring does not meet the standard; the seal ring selection is wrong.

        The actual use results show that the most ineffective part of the sealing element is the end face of the moving and stationary ring, the centrifugal pump is sealed, and the crack on the end face of the static ring is a common failure phenomenon. The main reasons are:

        1 When the sealing surface is too large, the flushing fluid can't take away the heat generated by the friction pair; the flushing liquid leaks away from the gap of the sealing surface, causing the end surface to overheat and damage.

        2 The liquid medium vaporizes and expands, so that the two end faces are separated by the vaporization expansion force. When the two sealing faces are pressed together, the lubricating film is broken and the surface of the end face is overheated.

        3 The liquid medium has poor lubricity, and the operating pressure is overloaded, and the tracking surfaces of the two sealing surfaces are not synchronized. For example, the high speed pump speed is 20445r/min, the center of the sealing surface is 7cm, and the line speed is up to 75 m/s after the pump is running. When there is a sealing surface lag, the rotation cannot be tracked, and the sealing surface is damaged by the instantaneous high temperature.

        4 The sealing rinsing liquid orifice plate or the filter screen is clogged, resulting in insufficient water and invalidation of the machine seal.

        In addition, the sealing surface surface of the sliding groove, the gap when the end surface is attached, the sealing element fails, the main reasons are:

        1 The liquid medium is not clean, and there are tiny hard particles, which slide the sealing surface at a high speed and scratch the surface of the end surface and fail.

        The pumping parts of the 2 pump are poor in coaxiality. After the pump is turned on, the end face is shaken once every revolution, and the running track of the moving ring is not concentric, causing the end face to vaporize and overheat and wear.

        3 The frequent occurrence of hydraulic characteristics of the liquid medium causes the pump unit to vibrate, causing the sealing surface to be misaligned and fail.

        Corrosion of the sealing medium by the liquid medium, stress concentration, coordination of soft and hard materials, erosion, auxiliary seal 0-ring, V-ring, concave ring and liquid medium are incompatible, deformation, etc. will cause mechanical seal surface damage failure, so The damage form should be comprehensively analyzed to find out the root cause and ensure that the mechanical seal runs for a long time.

        3.2. Requirements after the centrifugal pump stops running

        1 After the centrifugal pump stops running, the pump's population valve should be closed. After the pump is cooled, the valve of the auxiliary system is closed.

        2 High-temperature pump parking should be carried out according to the provisions of the equipment technical documents. After parking, it should be half-turned every 20 to 30 minutes until the pump temperature drops to 50 °C.

        3 When the cryopump is parked, when there is no special requirement, the pump should always be filled with liquid; the suction valve and the discharge valve should be kept normally open; the cryopump with double mechanical seal, the liquid level controller and the sealing liquid in the pump seal chamber The pumping pressure of the pump should be maintained.

        4 Pumps that are easy to crystallize, easy to solidify, and easy to precipitate, should be blocked after stopping the pump, and flush the pump and pipeline with water or other medium in time. 5 Discharge the liquid accumulated in the pump to prevent rust and cracking.

        3.3, the storage of centrifugal pumps

        1 The pump that has not been installed should be coated with a suitable rust inhibitor on the unpainted surface. The oil-lubricated bearing should be filled with the appropriate oil. The grease-lubricated bearing should be filled with only one grease. Use mixed grease.

        2 pumping clean liquid, flushing, suction line, discharge line, pump casing and impeller for a short time, and draining the pump casing, the suction line and the flushing liquid in the discharge line.

        3 rows of net bearing housing oil, then add clean oil, thoroughly clean the grease and refill with new grease.