Adjustable Residual Pump Design and Maintenance Technical Points 1 Design Aspects 1.1 Basic Structure The commonly used adjustable residual oil pump has the basic structure of oil-opening and segmental or multi-stage series. The structure of the oil flat open type is that the upper and lower pump bodies are butted through the oil leveling plane of the shaft center, and the inlet and outlet pipes, part of the volute and the runner are cast on the lower pump casing. 1 Design aspects 1.1 The basic structure of the adjustable residual oil pump is basically in the form of oil flat open and segmental or multi-stage tandem. The structure of the oil flat open type is that the upper and lower pump bodies are butted through the oil leveling surface of the shaft center, and the inlet and outlet pipes, part of the volute and the flow channel are cast on the lower pump casing, and the maintenance is relatively convenient, and the maintenance is not The upper casing of the pump can be removed directly by removing the pump line. The segmental structural feature is that each stage consists of an impeller located in the diffuser housing. The diffuser is connected by bolts and connecting rods. The Botaibang sections are also fixed in series by the fixed rods. The pressure is high and it is not easy to leak, but the inlet pipe must be disassembled during maintenance, which is difficult to disassemble and assemble. It is generally believed that the oil level open multistage pump is more rigid than the segment type multistage pump, and the pump vibration value is low. Garden tools are maintenance equipment for human green landscapes. They are used to maintain lawns, hedges, and protect flowers and trees, replacing most of the mechanized tools represented by manual labor. Classified according to use occasions, garden tools include garden tools and garden tools. According to the classification of the objects of use, it can also be divided into household tools and professional tools. Trees Hedge Shear,Household Tools,Multifunctional Garden Trowel,Folding Garden Trowel Rugao Yaou Import & Export Trade Co., Ltd , https://www.ntyaoumachinery.com
In the suction chamber structure, the oil-level open-type multistage pump generally adopts a semi-spiral shape, and the segment type multistage pump mostly adopts a circular ring shape. The extrusion chamber of each stage of the impeller is easy to manufacture, and the efficiency of converting liquid kinetic energy into pressure energy is high. The oil flat open multistage pump generally adopts a volute structure; however, due to the asymmetrical shape of the volute, it is easy to make The shaft is bent. The adjustable residual oil pump is limited to the first stage and the tail section. The volute is also used in the segment type multistage pump. In the middle stage, the guide wheel device is used to convert the energy between the primary impeller and the secondary impeller. .
The first stage impeller of the multistage pump is generally designed as a double suction impeller, and the other impellers are designed as a single suction impeller, especially for mediums with high temperature, large flow and easy to generate cavitation.
Adjustable Residual Oil Pump For pumps with very high pressure, it is difficult to withstand the pressure of a single-layer pump housing. A double-layer pump housing is often used to make the pump body into a cylinder type. The cylinder type pump body is subjected to a relatively high pressure, and the cylinder is provided with a flat open or segmented rotor.
1.2 Axial force balance 1.2.1 Common axial force balance measures The balance of the axial force of the adjustable residual oil pump generally includes: symmetric arrangement of the impeller, use of the balance drum device, balance plate device and balance drum, balance plate combination device, etc. Several. There are also double balance drum balancing mechanisms, such as high pressure boiler feed pumps. The impeller is symmetrically arranged or the balance drum is used. The axial force cannot be completely balanced. The thrust bearing is still required to bear the residual axial force. The adjustable residual oil pump is more balanced by a balance disc with automatic axial force adjustment. Axial force.
The adjustable residual oil pump must be equipped with a suitable balance line when designing the balance plate and balance drum of the multi-stage pump, so that the axial force balance device can meet the design requirements. In the multi-stage pump bearing temperature rise and bearing burnout accidents, many of them are caused by the small cross-flow area of ​​the balance pipe, the excessive loss of pipeline resistance, and the balance ability cannot meet the requirements.
For the adjustable residual oil pump, the balance plate and the balance plate seat are easy to be attached, which causes the balance plate and the pump to be damaged. The adjustable residual oil pump power wedge anti-wear balance plate is designed. The structure is similar to the principle of dry gas sealing of a centrifugal compressor: when the balance disc approaches the balance disc seat, the power wedge can generate a large opening force, thereby preventing the balance disc from adhering to the balance disc seat. After running the test, the balance plate works normally, and the working surface has no wear and scratches. It can be seen that the new power wedge anti-wear balance plate can effectively prevent the balance plate and the balance plate seat from being fitted. The power wedge balancing disc not only prolongs the life of the balance disc, but also reduces the leakage of the balance disc gap, saving energy and reducing consumption.
The adjustable residual oil pump is also based on the multi-stage pump axial force. It is caused by the fact that the impellers of each stage are oil suctioned on one side. It is proposed to improve the axial direction of the impeller by improving the pump body, impeller and stepped plate structure. The force is balanced so that there is no need to set up a balance disc, a balance drum, etc., and there is no need to consider the amount of axial yaw.
1.2.2 Limitations of balance disc and balance drum mechanism a) Variable working condition: When the pump starts and stops, the instantaneous axial force is supported by the direct contact between the balance disc and the balance disc holder. The friction may cause the balance disc and the seat bite. Death, dry burning, and even the accident that the pump shaft is twisted; when the load is abrupt, the axial force changes, and the rotor also pulsates axially, resulting in a sudden change in the gap between the balance plate and the seat, which is prone to cavitation and vibration. .
b) Liquid-solid two-phase flow medium: the medium pressure entering the balance plate, balance drum and other balancing mechanism is the output pressure of the pump. The pressure after the throttling is the inlet pressure of the pump, and the medium flows from the high pressure zone to the low pressure zone. Jet scouring, the solid particles in the liquid-solid two-phase flow medium will quickly abrade the balance plate, seat and other moving and static parts of the bad balance mechanism, and finally the pump can not operate normally.
1.3 Axis deflection adjustable slag pump pump shaft deflection is too large, it is easy to cause abnormal vibration, holding shaft, mechanical seal sealing surface uneven force and failure, etc., should design the radial force generation, minimize the pump shaft The deflection value in operation. The measures considered in the design are generally:
a) Adjustable residual oil pump uses a volute structure for multi-stage pump for diversion and energy conversion. The asymmetry of the shape of the volute is easy to bend the shaft during operation. The adjacent two-stage volute should be arranged 180° to reduce the diameter. Xiangli.
b) The number of stages of the pump impeller should not be too much. If necessary, increase the head of each stage of the impeller to ensure the total lift, so as to minimize the length of the pump shaft by reducing the number of pump impellers.
c) When selecting the adjustable residual oil pump shaft material, it is preferred to select materials with good mechanical properties such as strength and stiffness, taking into account the needs of the medium type and temperature.
d) When designing and calculating the diameter of the pump shaft, consider the factors such as transmission power, starting method, radial force, shaft deflection and related inertia load; consider the radial force that may be generated during non-design flow operation to resist bending deformation of the pump shaft Need.
e) Reasonably select the support point of the pump shaft.
1.4 Anti-vibration and vibration reduction The measures for anti-vibration and vibration reduction of multi-stage pumps that can also be considered in design are:
a) Control pump shaft deflection within the regular range.
b) Clearly require the pump shaft, impeller, etc. to perform dynamic and static balance tests.
c) The pump shaft of the multi-stage pump should be designed according to the rigid axis, and the working speed should be less than or equal to 0.75 times the first-order critical speed.
d) The impeller and the pump shaft are independently positioned in a single stage, and the impeller and the pump shaft are assembled by heating with an interference fit, which also improves the rigidity and critical speed of the rotor assembly.
e) When selecting the material such as the pump shaft and the impeller, select the material with good uniformity of the material itself, and select the material supply state and processing method that can ensure the uniform quality of the cross-section of the material.
f) Design suitable shaft and radial clearance to avoid vibration caused by abnormal friction of the rotor and stator and axial turbulence.
g) Multi-stage pump with balance disc to balance axial force, reasonable and correct design of the balance disc mechanism.
1.5 Vertical multi-stage pump For the vertical adjustable type residual oil pump, the general axial force is considered to be down when the normal operating conditions are considered. However, in the initial stage of driving, since the outlet pressure has not risen, the differential pressure before and after the impeller has not been established. There is an upward axial force, and some cause an axial upturn, accompanied by an organic seal, a bearing part overheating, a motor overcurrent phenomenon, and a rapid jump when it is severe. Structurally, the bearing bushing and the shaft should be relatively fixed so that the upward axial force is also balanced by the thrust bearing.
The balance disc device with automatic adjustment of axial force has a large size and requires a pressure relief oil return pipe. The axial force balance problem that cannot be installed due to the limitation of the caliper diameter has always been one of the high lift design. problem. An axial force balancing method has been introduced to expand the diameter of the impeller front cover to the edge of the inner wall of the pump so that the diameter of the impeller reaches a maximum value under the same diameter and the diameter of the rear cover of the impeller is appropriately reduced. The axial force is perfectly balanced.
Another new type of axial force balance device is introduced, which is equipped with a pair of dynamic and static friction pairs after the final stage impeller, the moving ring rotates with the impeller, the static ring does not rotate, and the front end of the end seal pair is the high pressure liquid at the exit of the final impeller. After the end face sealing pair is connected with the atmospheric pressure or the low pressure zone of the pump inlet, the axial force of the high and low pressure difference is formed by the seal.
1.6 Adjustable slag pump when conveying liquid-solid two-phase flow 1.6.1 Axial force balance The entire rotor component is axially turbulent, and the impeller collides with the middle partition and seal ring at high speed, causing chipping, which has caused Multiple malignant accidents occurred. In order to extend the overhaul life of this pump and slow down the wear rate of the seal gap, the following measures have been taken in design:
1 Improve the balance mechanism of the pump to make a balance disc holder (balance board) and two balance discs, which can reduce the leakage loss of the balance mechanism at the beginning of the pump operation, and ensure the safety and reliability of the pump in the later stage of operation. Life expectancy is also extended.
2 Impeller, seal ring, bushing, guide bushing, balance disc, balance disc seat, etc. are spray-welded.
1.6.2 Interstage and shaft end seals In order to overcome and avoid the abrasion of the hard particles in the liquid-solid two-phase flow medium between the rotating part and the stationary part, all the pump body sealing rings and the throttle sleeves and seals of the multistage pump The sleeve adopts a reverse spiral groove sealing structure to reduce particle abrasion.
The adjustable residual oil pump also adopts a combined sealing structure of a contactless labyrinth spiral seal and a mechanical seal at the shaft end, and is particularly suitable for a medium of liquid-solid two-phase flow.
1.6.3 The flow rate should be reduced from the pump speed, pump structure and other aspects to reduce the medium flow rate, and also reduce the erosion of the hard particles in the liquid-solid two-phase flow medium to the overcurrent parts of the multi-stage pump. The speed of the pump should be as low as possible, and it is not suitable to choose the speed of 1450 rpm.
2 Use and maintenance 2.1 Before the pump is turned on, when the high-temperature liquid that is transported suddenly enters the pump body of the multi-stage pump, the temperature of the pump body will change greatly. The pump body will be uneven due to uneven heating and thermal deformation. And the rotor parts are deformed, and there is only a small gap between the wear parts themselves, resulting in abnormal contact. If the device is started in this situation, it will cause vibration, bite, and shaft hung due to overheating. It is also said that when the pump is used to transport high-temperature liquid, it must be fully warmed before starting. The pump can only be started when the pump temperature is consistent.
2.2 In the operation, the adjustable residual oil pump balances the axial force by the balance mechanism such as the balance disc and the balance drum. The balance liquid flows out in the balance device, and the balance liquid is connected to the inlet end of the pump through the balance tube to ensure the normal operation of the pump:
a) The balance tube must not be blocked.
b) If fouling occurs in the balance pipe, it should be cleared in time.
c) Install a pressure gauge on the high pressure side of the balance tube to monitor the outlet pressure of the balance tube.
The adjustable type residual oil pump for conveying slurry adopts the balance plate. When operating, it needs to inject high-pressure sealing oil to make the balance plate and balance plate seat work in the clear oil to prevent the wear of the slurry and hard particles against the balance plate seat and the balance plate.
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