Here is a mini-dictionary of terms and definitions used in Slurry Pumping and in Minerals Process Industries.
Affinity Laws (also Affinity Rules) – Mathematical relationships of pump speed to flow rate, developed head and input power. When speed changes from N1 to N2, flow rate changes from Q1 to Q2=Q1(N2/N1), head from H1 to H2=H1(N2/N1)2 and power from Pi1 to Pi2=Pi1(N2/N1)3.
Beneficiation – The process of refining ores and raw materials.
Carrying Medium, in a slurry – Any homogenous fluid used to suspend solids during flow.
Characteristic Curve – A curve showing the relationship between pump heads and flow rates at a given speed.
Comminution – The reduction of size of solids particles by means of mill grinding, attrition or any other size reduction process.
Concentrates – The valuable portions of ores and raw materials obtained by a beneficiation process.
Concentration by Weight (or Mass) – The weight (mass) of solids present in a two-phase mixture taken as a percentage of the weight (mass) of the total mixture.
Concentration by Volume – The volume of solids present in a two-phase mixture taken as a percentage of the volume of the total mixture.
Consistency – A measure of the resistance of a slurry to shear. As with non-Newtonian fluids, the dynamic viscosity (being the ratio between shearing stress and rate of shearing strain) is not constant and must be determined for any particular flow rate.
Density of Material – Mass of material in kilograms per cubic metre. Material may refer to fluid, solid or mixture.
Drag Coefficient – A measure of the forces resisting the movement of a solid particle in a fluid.
Efficiency – The ratio of energy transferred to a pumped fluid and energy supplied to the pump shaft.
Fines – Small particles of ore or metal.
Flocculation – The use of high molecular weight synthetic organic polymers which are added to a suspension of finely divided solids in water, in very small quantities, which increase the settling rate of the suspended material by combining fine particles together to form a larger agglomerate.
Flotation – A continuous process in which cells are arranged in series forming a bank. Pulp enters the first cell of the bank and gives up some of its valuable mineral as a froth. Air bubbles overflow from this cell taking the desired mineral with them. The underflow from this cell passes to the second cell where more mineralized froth is removed, continuing down the bank, until barren tailings overflow and the underflow passes to the last cell in the bank. Pulp passing through each cell is drawn upwards into the rotor by the suction created by the rotation. Slurries are thoroughly mixed with the air before being broken into small, firm bubbles by the disperser, which surrounds the rotor, by abruptly diverting the whirling motion of the pulp.
Flow by Saltation – Turbulent flow of a slurry with solids too coarse to be fully suspended by turbulence. The solid particles travel by consecutive bounces and leaps on the bottom of the pipe.
Flow with Stationary Bed – The flow of a slurry in a pipe with restricted area due to a deposit of solid particles on the bottom of the pipe. The deposits often have dunes, both stationary and moving.
Flow rate (also Rate of Flow, Discharge and Capacity) – The volume of fluid a pump delivers during a certain period of time. This can be expressed in a variety of ways, such as litres per second, cubic metres per hour, gallons per minute, etc. Slurry pump applications are often specified in terms of tonnes of solids per hour and in such cases they must be converted to the appropriate volumetric units.
Friction loss – The resistance to flow within a pipe and fittings. It is a function of the rate of flow, viscosity of the liquid, and pipe diameter and is expressed in metres of fluid pumped
Head – The potential and/or kinetic energy that exists in a fluid. It is usually expressed in metres of fluid pumped.
Heterogeneous Slurry – A flowing slurry in which the concentration of solid particles is not uniform but increases towards the bottom of the pipe.
Homogenous Mixture or Slurry – A two-phase mixture of solid particles and fluid in which the two phases cannot be separated by mechanical means and in which the distribution or concentration of solid particles is uniform across the section of the pipe. In practice this is really a “model” slurry with uniform properties that we assume in order to simplify system calculations.
Hydraulic Gradient – The friction head loss per unit length of pipe.
Laminar Flow – In laminar flow, all the fluid particles proceed along parallel paths and there is no transverse component of velocity. The orderly progression is such that each particle follows exactly the path of the particle proceeding it without any deviation. Three-dimensional laminar flow can be viewed as concentric thin shells along the pipe axis. Laminar flow is associated with low velocities and viscous sluggish fluids.
Limiting settling velocity – The velocity of heterogeneous slurry in a horizontal pipeline, according to Durand’s studies, below which solids of a certain size, density and concentration begin to settle along the bottom.
Liner, Drive side (also Liner, Frame Plate Liner Insert) – A cast hard alloy or moulded rubber component lining the drive side of the pump casing.
Liner, Suction side (also Throatbush) – A cast hard alloy or moulded rubber component lining the suction side of the pump casing.
Liner, Volute (also Liner, Casing Shell) – A cast hard alloy or moulded rubber component lining the volute of the pump casing.
Mesh – The number of openings in a screen per linear mm (metric measurement) or inch (imperial measurement).
Mill – Machinery used for crushing and grinding ores.
Mixture – See Slurry
Mud, Paste or Sludge – A two-phase mixture of solid particles and fluid which is not a true homogenous mixture.
Newton – The force which imparts an acceleration of one metre per second squared to a mass of one kilogram.
Newtonian Fluid – A fluid exhibiting a direct relationship between shearing stress and rate of shear in laminar flow. The flow of Newtonian fluids is completely characterized by a single property, the viscosity, which is the ratio of shear stress and velocity gradient at any flow.
Non-Newtonian Fluid – A fluid exhibiting a variable relationship between shearing stress and either the rate of shearing strain (Bingham Plastic, Pseudoplastic and Dilatant fluids) or the duration of shear, i.e. Time dependence (Thixotropic and Rheopectic fluids). The flow of non-Newtonian fluids cannot be characterized by a unique property. The apparent viscosity of a non-Newtonian fluid is the ratio of shear stress and velocity gradient at one particular flow rate. It has no meaning at any other flow rate. Most solutions and suspensions at low concentrations behave as a Newtonian fluids, changing to non-Newtonian behavior when certain critical solids concentrations are reached. In the case of suspensions, critical concentrations depend on particle size and shape and on the degree of dispersion of the particles. For meaningful results, laboratory tests of NonNewtonian samples should be carried out only with fresh slurry samples from the actual system being evaluated.
NPSH – Net positive suction head. The total suction head in absolute units at the pump suction flange less the absolute vapor pressure of the liquid.
Particle Settling Velocity – The terminal, free-fall velocity of a solid particle falling in calm, clear water. The particle settling velocity is also used to describe the settling of slurries with low concentration of solids.
Reynolds number – A dimensionless number defining a fluid flow, expressed by the ratio of inertia forces and viscous forces.
Shaft Sleeve – A tubular hardened metal piece fitted over the shaft to protect it from wear by the gland packing in the stuffing box.
Shear rate – see Velocity gradient.
Slimes – A rock product which contains particles of not more than 5% +300 µm size nor less than 50% –75 µm size, and which includes all fine material produced by a comminution process.
Slurry – Strictly, a two-phase mixture of solid particles and fluid in which the two phases will not chemically react with each other and the two phases can be separated readily by mechanical means. However, in the terms “slurry” and “mixture” are used more loosely and interchangeably to describe a mix of any solids and liquids.
Slurry Settling Velocity – The velocity at which solids start to separates out of a suspension of solid particles before compaction is achieved.
Solids (also Solid Particles) – Fragments of solid materials which are chemically inert and will not react with the fluid in which they are suspended.
Specific Gravity – The ratio of the weight (or mass) of a substance to the weight (or mass) of an equal volume of water.
Specific Speed – A design index number used to classify pumps by impeller type and proportion. It is defined as the speed in revolutions per minute at which a geometrically similar pump would operate to deliver one unit of flow at one unit of head.
Stuffing Box – A portion of the pump casing through which the shaft extends and which holds a sealing device to prevent leakage. The sealing device can be a soft packed gland or a seal adaptor for a mechanical seal.
System Head curve (or System Resistance curve) – A curve showing the relationship between total heads required by a pumping system and their respective flow rates.
Transition Velocity – The velocity at which the flow of a slurry changes from one flow regime to another, such as from homogenous to heterogeneous flow or from laminar to turbulent flow.
Turbulent Flow – Flow at high Reynolds numbers with fluid and solid particles moving with random motion transverse to the main flow direction.
Velocity – Rate of motion in a given direction expressed in metres per second.
Velocity at limit of stationary deposition – Velocity of a heterogeneous slurry in a horizontal pipeline, according to Wilson’s studies, above which solid particles of a certain size and density will be picked up from the bottom and carried along by the flow.
Velocity gradient (also Shear rate) – A fluid in a pipe under laminar flow conditions moves axially in thin layers or concentric fluid shells. Velocities of successive shells increase from zero at the pipe wall to a maximum at the centre of the pipe. At any given radius ‘r’ there is a shell with velocity ‘v’. At the adjacent radius, reduced by ‘dr’, the respective velocity increase is ‘dv’. The velocity gradient is the ratio dv/dr. Note that the only useful velocity gradients are the ones ‘at the pipe wall’. These are the only values used in viscosity calculations.
Viscosity – Viscosity is the property of a Newtonian fluid in laminar flow to resist the relative displacement of adjoining layers, or concentric shells in a pipe. This resistance is due to internal friction and molecular attraction between particles which, when induced to flow, causes shear stress between adjacent layers.
Viscosity, Apparent – It is the Dynamic viscosity of non-Newtonian fluid, such as homogenous mixtures, muds, pastes, etc. Apparent viscosity changes value at different flow rates.
Viscosity, Dynamic – In Newtonian fluids it is the ratio of shearing stress and velocity gradient expressed in Pascal-seconds. Dynamic viscosity has a constant value at all flow rates.
Viscosity, Kinematic – In Newtonian fluids it is the ratio of dynamic viscosity and density of the fluid,expressed in seconds–2.
Hebei Tobee Pump Co.,Limited