Reliability Factors of Pumps
Reliability Issues – Centrifugal Slurry Pumps
Introduction
Pumps were probably the first machine ever developed, and are now the second most common machine in use around the world, out-numbered only by the electric motor. The very earliest type of pump is now known as a water wheel, Persian wheel or “noria”, consisting of a wheel of buckets that rotates to pick up water from a stream and dump it into a trough. Another early pump was the “Archimedean screw”, similar to the modern screw conveyor except that the flights were often fixed to the tube so that the whole arrangement would turn together. Both of these devices are still used, most commonly in basic agricultural applications. Pumps are now produced in an enormous range of types and sizes, for a very wide scope of applications, and this makes it difficult for any individual reference document or organisation to cover “pumps and pumping” as a general topic. So the broad field of pumping is classified into sub-divisions and then dealt with at that level. In the mining industry, the upper end of the pump scale includes impellers with diameters over 2.5m, slurry lines 10km long, particle size up to 100mm, flow rates handling more than 7000tph, and motors over 10MW. Finer slurries of around 1mm particle size are pumped for hundreds of kilometres in some operations. There are many ways to classify pumps. This just one of them. Pumps Displacement o Reciprocating Piston Diaphragm o Rotary Single rotor Vane Piston Flexible member Screw Peristaltic Multiple rotor Gear Lobe Circumferential piston Screw Dynamic o Centrifugal Axial flow Single stage Multi stage Mixed Flow Single suction Double suction Radial flowl Single stage Multi stage o Special Effect Jet Gas lift Hydraulic ram Electromagnetic This document only addresses centrifugal pumps, with a focus on single-stage radial-flow slurry pumps. Centrifugal pumps are capable of meeting duties of up to 1.4 m /s at
Introduction
Pumps were probably the first machine ever developed, and are now the second most common machine in use around the world, out-numbered only by the electric motor. The very earliest type of pump is now known as a water wheel, Persian wheel or “noria”, consisting of a wheel of buckets that rotates to pick up water from a stream and dump it into a trough. Another early pump was the “Archimedean screw”, similar to the modern screw conveyor except that the flights were often fixed to the tube so that the whole arrangement would turn together. Both of these devices are still used, most commonly in basic agricultural applications. Pumps are now produced in an enormous range of types and sizes, for a very wide scope of applications, and this makes it difficult for any individual reference document or organisation to cover “pumps and pumping” as a general topic. So the broad field of pumping is classified into sub-divisions and then dealt with at that level. In the mining industry, the upper end of the pump scale includes impellers with diameters over 2.5m, slurry lines 10km long, particle size up to 100mm, flow rates handling more than 7000tph, and motors over 10MW. Finer slurries of around 1mm particle size are pumped for hundreds of kilometres in some operations. There are many ways to classify pumps. This just one of them. Pumps Displacement o Reciprocating Piston Diaphragm o Rotary Single rotor Vane Piston Flexible member Screw Peristaltic Multiple rotor Gear Lobe Circumferential piston Screw Dynamic o Centrifugal Axial flow Single stage Multi stage Mixed Flow Single suction Double suction Radial flowl Single stage Multi stage o Special Effect Jet Gas lift Hydraulic ram Electromagnetic This document only addresses centrifugal pumps, with a focus on single-stage radial-flow slurry pumps. Centrifugal pumps are capable of meeting duties of up to 1.4 m /s at
References: Pump Handbook Third Edition; McGraw Hill; New York et al; 2002 Slurry Systems Handbook; B.E.Abulnaga; McGraw Hill; New York et al; 2001 API Standard 610 (Centrifugal pumps for refinery, heavy duty chemical and gas industry services) www.mcnallyinstitute.com (heaps of technical articles) www.lawrencepumps.com – The seven deadly sins of pump ownership Weir Slurry Pumping Manual