Features of Reciprocating Pumps
1. Strong self-priming ability;
2. The theoretical flow has nothing to do with the working pressure, but only depends on the speed, the size of the pump cylinder and the number of actions;
3. The rated discharge pressure has nothing to do with the size and speed of the pump;
4. Uneven flow;
5. The speed should not be too fast;
6. Not very sensitive to liquid contamination;
7. The structure is more complex and there are many wearing parts.
The structure and working principle of the reciprocating pump
The main components
Pump cylinder, piston, piston rod and suction valve, discharge valve.
The valve enters the pump cylinder. When the piston moves from right to left, the liquid in the cylinder is squeezed, the pressure increases, and it is discharged from the discharge valve. The piston reciprocates once, and each sucks and discharges a liquid, which is called a working cycle; this kind of pump is called a single-acting pump. If the piston goes back and forth once, and the liquid is sucked and discharged twice, it is called a double-action pump. The movement of the piston from one end to the other is called a stroke.
Flow and head of reciprocating pump
The flow rate of the reciprocating pump has nothing to do with the head, but is related to the size of the pump cylinder, the stroke of the piston and the number of reciprocations. The theoretical flow of the single-acting pump is QT=Asn The actual flow of the reciprocating pump is smaller than the theoretical flow, and decreases with the increase of the head, which is caused by leakage. The pressure head of the reciprocating pump has nothing to do with the flow rate of the pump and the geometric size of the pump, but is determined by factors such as the mechanical strength of the pump and the power of the prime mover.
The suction vacuum height also changes with the atmospheric pressure, liquid properties and temperature in the pump installation area, so the installation height of the reciprocating pump is also limited. The flow of the reciprocating pump cannot be regulated by the valve on the discharge pipeline, but should be realized by using a bypass pipe or changing the number of reciprocations of the piston and changing the stroke of the piston. The valve in the discharge line must be opened before the reciprocating pump is started. The piston of the reciprocating pump is connected to the prime mover by the connecting rod crankshaft. The prime mover can be either an electric motor or a steam engine. The reciprocating pump is suitable for the transportation of high pressure head, small flow and high viscosity liquid, but it is not suitable for the transportation of corrosive liquid. Sometimes it is directly driven by a steam engine to transport flammable and explosive liquids.
Advantages of reciprocating pumps
High discharge pressure can be obtained, and the flow rate is independent of pressure, with good suction performance and high efficiency;
In principle, any medium can be transported, almost not limited by the physical or chemical properties of the medium;
The performance of the pump does not change with the change of pressure and viscosity of the conveying medium.
The following pumps do not have the above-mentioned outstanding advantages of reciprocating pumps, but their structure is relatively simple, the use and operation are relatively convenient, and they also have the advantages of small size, light weight, uniform flow, and serialized mass production.
Disadvantages of reciprocating pumps
The flow is not very stable. Under the same flow rate, it is larger than the centrifugal pump; the mechanism is complex; the capital consumption is large; it is not easy to maintain, etc.
Ten applications of reciprocating pumps
1. Wastewater discharge from enterprise units.
2. Urban sewage treatment plant discharge system.
3. Subway, basement, civil air defense sewage pump system drainage station.
4. Sewage discharge from hospitals, hotels and high-rise buildings.
5. Sewage pumps are engraved for sewage drainage stations in residential areas.
6. Municipal engineering, discharge of thin mud in construction sites.
7. The water supply device of the waterworks.
8. Sewage discharge from farms and irrigation of rural farmland.
9. Exploration mines and water treatment equipment.
10. The sewage pump can replace the shoulders and suck the river mud.
