THE SELECTION STEPS OF SLURRY PUMP
Hebei Procast tech co.,ltd
The reasonable selection of slurry pump is one of the key factors to improve the service life of the pump. The reasonable selection of slurry pump includes reasonable selection of pump series, performance parameters, material of overcurrent parts, sealing type and transmission mode.
1. Selection of pump series
There are many types of centrifugal slurry pumps. Different series of pumps should be selected according to the nature of the slurry. Taking the Warman pump as an example, L-type pumps can be used for low-abrasive slurry with a weight concentration of less than 30%; High-strength and strong-abrasive slurry pumps can use AH pumps; when the liquid level changes greatly and needs to work under the liquid, SP (SPR), KZJL pumps should be used. When high-lift delivery is required. Choose ZGB, KZJ or HH pumps.
2. Selection of performance parameters
After the pump type is determined, the head and flow are the basis for selecting the pump size and whether it is connected in series. For conveying high-concentration and strong abrasive slurries, the pump's maximum rotation speed nmax (the highest rotation speed of various rotation speeds in the performance curve) is generally not selected. It is more appropriate to select a rotation speed of about 3/4nmax. When the selected pump is at 3/4 nmax, the flow rate is appropriate but the head cannot be reached, and multiple pumps can be used in series. For Warman pumps, the flow range must be limited for different slurries; for high-concentration and strong-abrasive slurries, the flow rate should be selected within the range of 40-80% of the pump's maximum efficiency; for low-concentration abrasion slurries, The flow rate should be selected within the range of 40%-100% of the flow rate corresponding to the highest pump efficiency. Generally, it is not selected within the range of 100%-120% of the flow rate corresponding to the highest efficiency.
3. Head margin
During the operation of the slurry pump, due to the wear of the wet parts, the performance of the pump continues to decline until it finally fails to meet the working conditions. In order to enable the pump to run for a long time in the vicinity of the rated working conditions, usually a head margin is added when the pump is selected. The general margin is 10% of the rated head.
4. Material selection of wet parts
There are many materials available for the wet parts of the slurry pump, which should be determined according to the physical properties (particle composition, particle size, shape, hardness, concentration) and chemical properties (acid, alkali, oil) characteristics of the slurry transported.
Metal wear-resistant material hard nickel 1#, has good abrasion resistance to coarse particles;
Hard nickel 4# has abrasion resistance close to hard nickel 1#, but for large particles, high-stress impact slurries have better abrasion resistance, and the price is higher than hard nickel 1#;
The abrasion resistance of chromium 27 wear-resistant cast iron is similar to hard nickel 1#. In terms of alkaline mixed liquid, it has better corrosion resistance and the price is higher than hard nickel 1#.
Cr15Mo3 is currently recognized as an excellent anti-abrasion material in the world, with a macro hardness as high as Brinell hardness of 650-750. It has good anti-abrasion performance for coarse-grained strong abrasive slurry, but it is relatively expensive and brittle.
There are many varieties of rubber materials, mainly suitable for fine particles without sharp edges. Natural rubber is suitable for conveying weak acids. Weak alkaline slurry, large abrasive particle size and speed within a certain range, 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℃, it has excellent abrasion resistance in oil slurry. In the application of slurry pump materials, rubber has been rapidly developed due to its excellent wear resistance, corrosion resistance and cavitation resistance, especially in the flue gas desulfurization working conditions of power plants, and the service life can reach five years.
5. Selection of shaft seal
Slurry pumps mainly have shaft seals such as packing seal, expeller seal and mechanical seal.
The expeller seal is generally used under flood. The high pipe pressure 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 the auxiliary impeller seal reduces power consumption and is generally about 5% of the rated power. .
Packing seal needs to add shaft seal water, and to ensure sufficient water pressure and water volume, the shaft seal water pressure is equal to the pump outlet pressure plus 35Kpa. Mechanical seal needs to add shaft seal water, good sealing, no leakage.
6. Transmission arrangement
The transmission arrangement of the slurry pump is V-belt transmission, elastic coupling transmission, gear box transmission, hydraulic coupling transmission, frequency conversion drive device, and thyristor speed regulation. Among them, the elastic coupling and the V-belt are cheap and easy to disassemble and install, and should be given priority. But the V-belt will increase power consumption by 5%.
There are many types of pump installations. CV transmission, DCZ transmission, CRZ transmission and ZVZ transmission. There are 8 installation directions shown at the pump outlet. CV and ZV transmissions are within the rated power range of the bracket, and large-size motors will be limited.
7. Equipped with motor
After the pump shaft power is calculated, considering the factors such as pump start-up and flow fluctuations, a standard motor should be selected to have a certain power richness factor. Generally, the rich system is 1.1-1.2, the high power takes a small value, and the small power takes a large value.