Selection Steps Of Slurry Pump And Several Problems That Should Be Paid Attention To
Reasonable selection of slurry pump expeller is one of the key factors to improve the service life of the pump. Reasonable selection of slurry pump includes reasonable selection of pump type, performance parameters, material of over-current parts, seal type and transmission mode.
1. Selection of pump type
There are many types of centrifugal slurry pumps. Different types of pumps should be selected according to the nature of the slurry. Taking Warman pumps as an example, L-type pumps for low-abrasive slurry with a concentration of less than 30% can be selected AH type pumps can be used for high-concentration and strong abrasive slurry pumps; when the liquid level changes greatly and needs to work under liquid, SP (SPR), KZJL type pumps should be selected. When high head conveyance is required. Use ZGB, KZJ or HH pumps.
2. Selection of performance parameters
After the pump type is determined, the head and flow are the basis for choosing the size of the pump and whether it is connected in series. When conveying high-concentration and highly abrasive slurry, the maximum number of pumps nmax (the highest number of rotations in the performance curve) is generally not selected. It is more appropriate to choose a number of rotations of about 3 / 4nmax. When the selected pump is at 3/4 nmax, the flow is appropriate but the head cannot be reached. Multiple pumps can be used in series. For Warman pumps, the flow range of different slurries should also be limited; for high-concentration and strong-abrasive slurry, the flow rate should be selected within the range of 40-80% of the pump's highest efficiency; The flow rate should be selected within the range of 40% -100% of the corresponding flow rate of the pump. Generally, it is not selected in the range of 100% -120% of the corresponding flow of the highest efficiency.
3.Head Margin
During the operation of the slurry pump, due to the wear of the over-current components, the pump performance continued to decline until it finally failed to meet the working condition requirements. In order to enable the pump to run for a long time near the rated operating conditions, a headroom is usually added when the pump is selected. The general margin is 10% of the rated head.
4.Selection of material for overcurrent parts
There are many materials that can be used for the slurry pump's over-flow parts, which should be determined according to the characteristics of the room (particle composition, particle size, shape, hardness, concentration) and chemical (acid, alkali, oil) used to convey the slurry.
Metal wear-resistant material hard nickel 1 #, has good abrasion resistance to coarse particles;
Hard nickel 4 # has abrasion resistance similar to hard nickel 1 # (public account: pump housekeeper), but for large particles, high stress impact slurry has better abrasion resistance and the price is higher than hard nickel 1 #;
The wear resistance of chromium 27 wear-resistant cast iron is similar to that of hard nickel 1 #. As far as the alkaline mixture is concerned, it has better corrosion resistance and the price is higher than that of hard nickel 1 #.
Cr15Mo3 is currently recognized as an excellent anti-abrasive material in the world. Its macro hardness is as high as 650-750 Brinell hardness. It has good anti-abrasive performance against coarse abrasive slurry, but it is expensive and brittle.
There are many types of rubber materials, which are mainly suitable for fine particles without sharp edges. Natural rubber is suitable for transporting weak acids. In the range of weak alkaline slurry, large abrasive grain size and certain speed, natural rubber is more durable than other metal or rubber elastic materials. Neoprene is not as good as natural rubber, but when the temperature is lower than 200 ° C, it has excellent abrasion resistance in oil slurry. In the application of slurry pump materials, rubber has developed rapidly due to its excellent abrasion resistance, corrosion resistance, and cavitation resistance, especially in the flue gas desulfurization conditions of power plants, which has a service life of up to five years.
5.Selection of shaft seal type
Slurry pumps mainly include shaft seals such as packing seals, auxiliary impeller seals, and mechanical seals.
The auxiliary impeller seal is generally used under reverse irrigation work. The pressure of the high pipe should be less than 10% of the pump outlet pressure. This type of shaft seal does not add shaft seal water, but the use of auxiliary impeller seals to increase power consumption is generally about 5% of the rated power. .
Shaft seal water needs to be added to the packing seal, and sufficient water pressure and water volume must be guaranteed. The shaft seal water pressure is equal to the pump outlet pressure plus 35Kpa. Mechanical seals need to be added with shaft seal water, which has good tightness and no leakage.
6.Transmission method
The transmission method of the slurry pump includes V-shaped V-belt drive, elastic coupling drive, gear reducer drive, hydraulic coupler drive, variable frequency drive, and SCR speed control. Among them, flexible couplings and V-belts are cheap and easy to assemble and disassemble. They should be given priority to be used. But V-belts will increase power consumption by 5%.
7.With motor
After the pump shaft power is calculated, taking into account factors such as pump startup and flow fluctuations, a certain power richness factor should be selected when selecting a standard motor. Generally, the affluent system is 1.1-1.2, the high power is the small value, and the small power is the large value.
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