The main features of single-stage single-suction horizontal centrifugal pump
1. Stable operation: The absolute concentricity of the pump shaft and the excellent dynamic and static balance of the impeller ensure smooth operation and no vibration.
2. Leak-proof: The hard alloy seals of different materials ensure that there is no leakage in the transportation of different media.
3. Low noise: The water pump supported by two low-noise bearings runs smoothly, except for the weak sound of the motor, and there is basically no noise.
4. Low failure rate: the structure is simple and reasonable, the key parts are equipped with world-class quality, and the trouble-free working time of the whole machine is greatly improved.
5. Convenient maintenance: It is easy and convenient to replace seals and bearings.
6. More space-saving: horizontal single-stage centrifugal pump is horizontal suction and vertical discharge.
Basic structure of single-stage single-suction horizontal centrifugal pump
The centrifugal pump is composed of many parts. The following uses the single-stage single-suction horizontal centrifugal pump common in water supply and drainage engineering as an example to explain the role, material and composition of each part.
1. Impeller
1. The impeller is the main part of the centrifugal pump. The shape and size of the impeller are determined by hydraulic calculation. When choosing the impeller material, in addition to the mechanical strength under the action of centrifugal force, the wear resistance and corrosion resistance of the material must also be considered. At present, most impellers use cast iron, cast steel and bronze city.
2. The impeller can be generally divided into two types: single suction impeller and double suction impeller. The single-suction impeller absorbs water unilaterally, and the front cover and the rear cover of the impeller are asymmetric. The double-suction impeller absorbs water on both sides, and the impeller cover is symmetrical. Generally, most large-flow centrifugal pumps use double-suction impellers.
3. Impeller can be divided into closed impeller, open impeller and semi-open impeller according to its cover. Any impeller with two cover plates is called a closed impeller, which is the most widely used. If only the rear cover plate does not have the front cover plate, it is called a semi-open impeller. It is generally used to pump sewage pumps containing suspended matter. In order to avoid clogging, sometimes a semi-open or full-open impeller is used. This type of impeller is characterized by blades. Less, generally only 2~5 tablets.
Second, the pump shaft
The pump shaft uses a rotating impeller, and the commonly used materials are carbon steel and stainless steel. The pump shaft should have sufficient strength and stiffness, and its radius should not exceed the allowable value; the working speed should not be close to the critical number of revolutions that cause resonance. The impeller and shaft are connected by a key. The key is the connecting piece between the rotating bodies. Flat keys are generally used in centrifugal pumps. This key can only transmit torque and cannot fix the axial position of the impeller. In large and medium-sized water pumps, the axial position of the impeller is usually located by using a sleeve and tightening the sleeve to deteriorate the nut.
3. Pump casing
1. The pump casing of the centrifugal pump is usually cast into a volute shape, and its water passing part requires good hydraulic conditions. When the impeller is working, the flow rate gradually increases along the gradually expanding section of the volute. In order to reduce the hydraulic loss, the speed of the water flowing along the gradually expanding section of the volute should be a constant in the design of the pump. After being discharged from the volute, the water flows into the pressurized water pipe through the conical diffusion pipe. The role of the cone-shaped diffuser on the volute is to reduce the speed of the water flow, so that a part of the velocity head is converted into a pressure head.
2. The material selection of the pump casing, in addition to considering the corrosion and wear of the medium to the overcurrent part, should also make the casing have sufficient mechanical strength as a pressure-resistant container.
4. Pump base
The flange hole on the pump base and fixed with the bottom plate or foundation. The top of the pump casing is provided with a screw hole for filling water and deflating, so as to be used for filling water and exhausting the air in the pump casing before the pump is started. The flange hole of the spinal canal for suction and pressure of the water pump is provided with a pressure measuring screw hole for installing a vacuum gauge and a pressure gauge. The bottom of the pump casing is provided with a water discharge screw hole, which is used for emptying the accumulated water when the pump is stopped for maintenance. In addition, the bottom of the transverse groove of the pump base is provided with a drain screw hole to drain away the leaking water droplets flowing out of the packing box at any time. All these screw holes can be tightened with threaded plugs if they are temporarily useless during the movement of the pump.
5. Shaft sealing device
When the pump shaft passes through the pump casing, there is a gap between the shaft and the casing. If no measures are taken, the gap will leak. When the liquid pressure at the gap is greater than atmospheric pressure (such as a single-suction centrifugal pump), the high-pressure water in the pump casing will leak out through this gap to a large amount; when the liquid pressure at the gap is vacuum (such as a double-suction centrifugal pump) ), the atmosphere will leak into the pump from the gap, thereby reducing the water absorption performance of the pump. For this reason, it is necessary to provide a sealing device at the gap between the shaft shells, called the shaft seal. At present, shaft seals that are widely used include packing seals and mechanical seals.
1. Packing seal
Packing, also known as packing, plays a sealing role against water or gas in the shaft sealing device. The commonly used fillers are asbestos rope fillers impregnated with oil and graphite. In order to improve the sealing effect, the packing rope is generally made into a rectangular section. The packing is pressed with a gland. The gland is also called "grand", and it can adjust the degree of compression of the packing by loosening the bolts that tighten the gland. The gland is pressed too loosely, the sealing effect is not achieved, and the pressure is too tight, the mechanical wear of the pump shaft and the packing is large, and the power consumption is also large. If it is pressed too tightly, it may even cause a shaft holding phenomenon, resulting in severe heat generation and wear. Generally, the water in the water-sealed pipe can seep through the gap between the fillers and drip out. The packing seal has a simple structure and reliable operation. However, the life of the packing is not long, and there is no guarantee that the toxic, corrosive and precious liquid will not leak.
2. Model seal
The model seal is also called end seal. Its basic components and working principle are shown in the figure, mainly composed of moving ring 5., static ring 6, pressing element (spring 2) and sealing element (sealing ring 4, 7). The pressure of the liquid in the sealing ring of the moving ring and the pressure of the pressing element make its end face fit the end face of the static ring, and generate an appropriate specific pressure on the end face A of the two rings and maintain a very thin liquid film. To achieve the purpose of sealing. The gap B between the moving ring and the shaft is sealed by the moving ring seal 4, and the gap C between the static ring and the gland is sealed by the static ring seal 7. The three seals formed in this way (that is, the seals at the three interfaces A, B, and C) block all possible ways for the liquid in the sealed cavity to leak outward.
6. Leak reduction ring
There is a rotating joint between the outer circle of the impeller suction port and the inner wall of the pump casing. It has a formal high and low pressure interface and has a relatively moving part, which is easy to leak. In order to reduce the return flow of high-pressure water in the pump casing to the suction port, two leakage reduction methods are generally used in the structure of the pump:
(1) Reduce the joint gap (no more than 0.1~0.5mm);
(2) Increase the resistance in the leakage channel.
Because the gap at the joint is prone to wear of the impeller and the pump casing, in order to prolong the service life of the impeller and the pump casing, a metal mouth ring is usually inlaid on the pump casing, and the joint surface of this mouth ring can be made into a multi-tooth shape. In order to increase the backflow resistance of the water flow and improve the leakage reduction effect, this ring is generally called a leakage reduction ring.
Seven, bearing seat
The bearing housing is used to support the bearing, and the bearing is installed in the bearing housing as a supporting part of the rotating body. The bearings commonly used in water pumps are rolling bearings and sliding bearings. According to the load, it is divided into ball bearings and roller bearings. Generally, roller bearings are used.
8. Coupling
The output of the motor is transmitted to the water pump through the coupling. Couplings, also known as "backrest wheels", are available in both rigid and radial styles. The rigid coupling is connected by two circular flanges. There is no room for adjustment in the connection between the pump shaft and the motor. Therefore, it requires high installation accuracy. It is often used for the connection of small pumps combined with vertical pump units. . Radial coupling is a coupling with a steel pin and an elastic rubber ring, which is often used in the installation of large and medium-sized horizontal pump units.
Nine, axial force balance measures
Due to the lack of symmetry of the impeller, when the centrifugal pump is working, the pressure acting on both sides of the impeller is not equal, and a special axial force balancing device must be used to solve it. For single-stage single-suction centrifugal pumps, it is generally adopted to drill a balancing hole in the rear cover plate of the impeller, and install a leakage reduction ring on the rear cover. When the pressure water passes through the leakage reduction ring, the pressure drops and flows back into the impeller through the balance hole, so that the pressure on the rear cover of the impeller is close to the front cover, so that the axial thrust is eliminated.
Single-stage single-suction horizontal centrifugal pump installation and precautions
1. Whether the installation of the pump is reasonable has an extremely important impact on the normal operation and service life of the pump, so installation and calibration must be carried out carefully.
2. Pre-embed the base bolts according to the installation size to do the concrete foundation work.
3. After the foundation cement is solidified, install the pump on the foundation and use a spirit level to check the level of the pump and the motor shaft. If it is not level, use the horn to adjust it to the level. Tighten the foot nut after adjustment.
4. Check whether the rotating parts of the pump are jammed and rubbed. The coaxiality of the pump shaft and the motor should be strictly checked. The flake can be adjusted to make it concentric. Finally, the coupling can be rotated by hand. The rotation is easy and even without rubbing. As normal.
5. The suction and discharge pipelines of the pump should have their own brackets. The weight of the pipeline should not be directly borne by the pump to avoid crushing the pump.
6. When the installation position of the pump is higher than the liquid level (within the suction range of the pump), a bottom valve should be installed at the end of the suction line, and a filling screw hole or valve should be provided on the discharge line for the pump to start For pre-filling; when the installation position of the pump is lower than the liquid level, control valves and filter devices should be installed on the suction pipe to prevent debris from being sucked into the pump. The filtration area should be greater than 3-4 times the pipe area.
7. Pumps with high heads should also be installed with check valves on the outer end of the outlet flow control valve to prevent water hammer damage during sudden shutdown.
8. The installation height of the pump must be in accordance with the cavitation allowance of the pump, and the pipeline loss and medium temperature must be considered.
Maintenance and maintenance of single-stage single-suction centrifugal pump
1. Regular maintenance
(1) For the pump type using grease, the grease is generally replaced every 6 months or so. The grease used is 4# disulfide grease, but if the grease color is dark, there are water beads on it, the grease hardens or deteriorates or If the bearing becomes hot, replace the grease immediately. When replacing, clear the old oil, wash the bearing and the shaft cover, then add grease, the amount of grease added should be added to the bearing chamber 1/2-2/3;
(2) Pump set lubricated with lubricating oil. In case of deterioration of the lubricant, replace the lubricant. When changing the lubricating oil, first stop, open the plug at the lower end of the suspension oil chamber, put the lubricating oil clean, reinstall the plug, and inject oil from the oil hole cover to the normal position.
2. If the pump is stopped for a long time, the pump should be disassembled, cleaned and oiled, packaged for storage, and if stored for more than 6 months, the oil seal surface of all oil seal parts should be re-sealed.
The above are the main features, basic structure, installation and precautions, maintenance and maintenance of the single-stage single-suction horizontal centrifugal pump explained to everyone. About the knowledge of single-stage single-suction horizontal centrifugal pump, I will introduce it here first, I hope this knowledge can help everyone! It should be known that single-stage single-suction horizontal centrifugal pumps are still widely used in daily life. If you want to ensure its operating efficiency and extend its service life, then it is recommended that you follow the safety rules during use and then use it again. Maintain it, if there are some failure problems that cannot be solved by yourself, then you can send them to a professional maintenance organization for repairs. Never disassemble them yourself to prevent failures from escalating. Only in this way can it extend its service life and bring you more High use effect.
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