Proper slurry pump selection is one key factor in extending the service life of the pumps. This includes choosing the suitable pump type, performance parameters, material for flow passage components, sealing type, and transmission method.
Selection of Pump Type
There are many types of centrifugal slurry pumps. Different types of pumps should be selected based on the properties of the slurry. Using Warman pumps as a reference, for low-erosive slurry with a weight concentration below 30%, an L-type pump can be selected; for high-concentration and highly erosive slurry, an AH-type pump is recommended; when the liquid level changes significantly and the pump needs to work submerged, an SP (SPR) type pump should be chosen. When high-head transfer is required, the ZGB-type pump should be selected.
Selection of Performance Parameters
Once the pump type is determined, head and flow rate are the basis for selecting the pump size and whether to use a series connection. When conveying high-concentration and highly erosive slurry, it is generally not recommended to select the highest speed (nmax) on the performance curve. Instead, a speed around 3/4 of nmax is more appropriate. While the pump has the appropriate flow rate but insufficient head at 3/4 nmax, multiple pumps can be connected in series. For Warman pumps, the flow rate range should also be limited based on the type of slurry. For high-concentration and highly erosive slurry, the flow rate should be within 40% to 80% of the pump’s best efficiency point flow rate. For low-concentration and less erosive slurry, the flow rate should be within 40% to 100% of the best efficiency point flow rate. Generally, flow rates within 100% to 120% of the best efficiency point flow rate are not recommended.
Head Margin
During operation, the performance of a slurry pump gradually decreases due to the wear of the flow passage components, until it can no longer meet the working conditions. To ensure that the pump can operate near the rated conditions for a long time, a head margin is usually added when selecting the pump. The margin is generally 10% of the rated head.
Selection of Material for Flow Passage Components
There are many materials available for the flow passage components of slurry pumps. The selection should be based on the physical (particle composition, size, shape, hardness, concentration) and chemical (acid, alkali, oil) characteristics of the slurry being conveyed.
Selection of Shaft Seal Type
Slurry pumps mainly have packing seals, secondary impeller seals, and mechanical seals. Secondary impeller seals are generally used in suction-lift applications, with the maximum pressure being less than 10% of the pump’s outlet pressure. This type of seal does not require seal water, but using a secondary impeller seal will increase power consumption, typically by about 5% of the rated power. Packing seals require seal water with sufficient pressure and flow rate, with the seal water pressure equal to the pump’s outlet pressure plus 35 kPa. Mechanical seals also require seal water, and they offer good sealing performance with no leakage.
Transmission Method
The transmission methods for slurry pumps include V-belt transmission, flexible coupling transmission, gear reducer transmission, fluid coupling transmission, variable frequency transmission, and thyristor speed control. Flexible couplings and V-belts are cheap and easy to install and remove, so they should be given priority. However, V-belts will increase power consumption by about 5%.
Installation Type
Slurry pumps have several installation types, including CV transmission, DCZ transmission, CRZ transmission, and ZVZ transmission.
er the pump shaft power is calculated, considering factors such as pump startup and flow rate fluctuations, a standard motor should be selected with a certain power margin. The margin is generally taken as 1.1 to 1.2. For high-power applications, a smaller value should be used, while for low-power applications, a larger value is preferred.
