What are the structural characteristics and advantages of multi-stage pumps

Category: Water pump knowledge

2024-05-23

Multi-stage pump is a simple series of many single-stage pumps, such as vertical multi-stage centrifugal pumps, combined together, his output water pressure can be very large. With the progress of technology, the pump of single-stage impeller can increase the head of the pump by increasing the speed of the pump, which can replace the multi-stage pump, but the price is a little more expensive. When the actual lift of the pump is less than 125 meters, the selection of single-stage pump or multi-stage pump can be considered according to the pump room area, pump price (multi-stage pump is generally higher than single-stage pump price), and other factors.

The difference between multi-stage pump and single-stage pump is that it has more than 2 impellers and its head is changeable. For example, the head of some horizontal multi-stage pumps has a minimum of 75 meters and a maximum of 685 meters. A multistage pump is a complex of two or more single-stage pumps. The single-stage pump is easy to operate, relatively stable in performance, small in size and light in weight, so it is easy to handle. The degree of integration of Dalian multi-stage pump is high, but the operation is complex and the maintenance is difficult.

Multi-stage pumps can be divided into vertical multi-stage pumps and horizontal multi-stage pumps. From the material can be divided into stainless steel multistage pump, LG multistage pump, MD multistage pump, fluorine plastic multistage pump and so on. Multistage pump transport material method is through the rotation of the impeller, access to centrifugal force. In addition, the gas density in the pump body will be continuously compressed and then gradually pumped out, thus creating a vacuum transport environment. Dalian multi-stage pump is widely used in petrochemical, machinery, minerals, and even medicine and food industries. Its uses include vacuum filtration, vacuum evaporation, vacuum degassing, vacuum water diversion, vacuum concentration, vacuum moisture regain and vacuum feeding, etc. Among them, there are many transportable materials, even flammable and explosive gases, which can filter dust and water-bearing gases in the industrial production environment, which has a great role in promoting the development of the industry.

1. Shell structure

Single shell pump can be operated under high pressure, but the two high temperature resistance and thermal shock resistance are different. The upper limit of high temperature resistance of ordinary single shell pump is 180~320 ℃, and some specially designed pumps can be used to about 400 ℃. The double shell pump can basically use 400~450 ℃, and good thermal shock resistance. However, the double-shell pump has a large weight and volume, inconvenient manufacturing and high price. Generally used only in large, high pressure with strong thermal shock occasions. Ethylene plant BTX feed pump working conditions there is a certain thermal shock, but according to the past experience, some single shell form of the pump can also meet the requirements of use.

2. Axial middle pump and radial split pump

Abroad for the petrochemical industry can meet the requirements of a certain temperature and pressure resistance of the single shell, high lift, small flow multi-stage pump, basically is an axial open structure. In addition to the convenience of assembly and disassembly and maintenance, the medium-open type has better thermal shock resistance than the radial split pump fixed with a bar, so the BTX feed pump in the ethylene plant adopts the medium-open structure. Although the medium-open Dalian multi-stage pump series can meet other technical indicators, the flow rate is too large, so the pump factory can consider extending the pump series to the direction of small flow rate.

3. Shaft seal

Although the requirements for shaft seals are high, single-end mechanical seals have been able to meet the requirements. However, because the pressure is high, the medium viscosity is small, generally should choose the built-in balanced mechanical seal.

4. Wear-resistant seal ring

Due to the low viscosity of the medium (2.1~3.1mPa.s), in order to reduce internal leakage, improve efficiency, and maintain stable performance of the pump when the temperature changes, wear-resistant sealing rings are generally set on the impeller and the pump body.

Single-stage pump refers to a pump with only one impeller, with a maximum head of only 125 meters. Multi-stage pump refers to a pump with two or more impellers, and the maximum lift can exceed 125 meters. Multi-stage pump can be equipped with four-stage motors by increasing the number of impellers when the lift of single-stage pump needs to be equipped with two-stage motors, thus improving the service life of the pump and reducing the noise of the unit. However, maintenance of multi-stage pump is a little more difficult than that of single-stage pump.

5. Center line support horizontal key positioning

When the horizontal pump temperature exceeds 177 ℃, the pump body supported by the centerline is usually used to avoid the one-way expansion of the pump body after heating endangers the normal operation of the pump. At the same time, the support surface should be provided with a horizontal key to fix the axial position of the pump.

6. Bearing cooling

BTX feed pump in the catalyst regeneration, the operating temperature is close to the upper limit, the general should be to cool the bearing box, reduce the oil temperature.

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