Guidelines for slurry pumping

Slurry A mixture of solids and liquid, generally water. The particles may not be abrasive although this is common.

• Where are slurry pumps used? • Can submersible slurry pumps replace other types of pumps? • Which parts are of special importance in a submersible slurry pump? • Which parameters of the slurry and pipe system are required to be able to dimension a pump correctly? The purpose of this book is, in a simple way, to describe slurry pumps, slurry pumping and the various parameters required when selecting submersible slurry pumps. To provide a deeper understanding of the calculations, a manual calculation example is given in the appendix of the book. about the type of slurry, the choice of pump, the...

Slurry pumps are a heavy and robust version of centrifugal pumps, capable of handling tough and abrasive duties. Slurry pumps should also be considered a generic term, to distinguish them from other centrifugal pumps mainly intended for clear liquids. Slurry pumps are used to move mixtures of liquid and solids in many industries with a broad spectrum of applications, for example mine drainage, dredging of settling lagoons and pumping of drilling mud. • To pump a medium where abrasive particles are present • To transport as much solids as possible, hydraulically • To pump the end product in a...

Slurry pump types Three main types of pumps are used for slurry pumping: • Horizontal slurry pumps • Vertical slurry pumps • Submersible slurry pumps These types of pumps are often called dry mounted as the hydraulic end and the drive unit are located outside the sump. It is the main group of slurry pumps and they are available for a wide range of head and flow conditions and material options. These types of pumps normally use standardized electrical motors and seals. In plants where there is a risk of flooding, there can be reasons for replacing a horizontal pump by a dry-mounted, submersible,...

Cantilever/sump pumps are considered as semi-dry installed, as the hydraulic end is lowered into the slurry, but the drive unit and support structure are dry installed. Similarly to tank pumps there are no submerged bearings or shaft seals, but a long shaft overhang. Depending on size the pump is either mounted with a base plate over the sump or hung from the roof. Cantilever-pumps have a number of disadvantages which make them suitable for replacement with submersible pumps: • Long distance between motor and volute makes the pump bulky to handle. • Limited access to the sump. Problems with sediment...

Grindex slurry pumps The main difference between slurry and standard dewatering pumps is in the parts that are in direct contact with the slurry and thus subject to wear by the slurry’s solid particles. Important factors for slurry pumps such as cooling, seals and especially the hydraulic design, are described in this chapter. Grindex Bravo slurry pump equipped with cooling jacket and agitator Cooling jacket Inspection chamber

Drive unit Motor Important factors for slurry pump motors: • Effective cooling • Insulation Effective cooling Water cooling is superior to air cooling and gives the submerged motor a high power density and comparatively low temperature. Standard motor design Standard motor design Standard motor design In the Grindex motor the rotor diameter is bigger and the stator thinner than in standard motors. This directs more of the losses (heat release) to the stator and to the surrounding, cooling liquid. The short heat transfer distance makes the cooling effective and keeps the working temperature low....

Class H insulation (180°C) is applied to the stator winding by a trickle impregnation system. The Grindex Bravo pump has a motor limit to Class B (140°), which reduces thermal stress resulting in extended lifetime. Trickle impregnation gives a winding fill much greater than typical dip and bake systems. This gives much higher protection against short circuits in the winding. Shaft and bearings Important factors for shafts and bearings: • Shaft design and dimensioning • Bearing type and protection Shaft design and dimensioning The shaft and bearings are of sturdy design. The distance between the...

Important factors for submersible pump seals: • Low leakage or even zero leakage! • Wear resistance Leakage and wear resistance In conjunction with leakage rate, the most important feature for seals in slurry applications is the ability to resist wear from abrasive particles. The seals for the slurry pumps are designed to cope with highly abrasive pump media. Only the seal rings are exposed to the media. Other parts of the seal, such as springs and torque locks are protected from wear, clogging and corrosion inside the seal housing. In addition, an isolation zone takes the pressure of the mechanical...

Protection systems Important factors for submersible pump protection: • The possibility of detecting a leaking seal before any damage occurs • Spin-out™ seal protection • Overheating protection Possibility of detecting a leaking seal Stator housing leakage: A float switch shuts the pump down if water is detected. The inspection chamber between the seal unit and the bearings has a built-in sensor for early detection of fluid leakage. The space can be inspected and emptied via a screw, which is easily accessible from the outside. Spin-out™ seal protection A patented outer seal design that protects...

Hydraulic design Important factors for submersible pump hydraulic parts: • Efficiency • Wear • Agitator Efficiency Pumping slurry can cause a severe reduction in the hydraulic efficiency of a pump. The Grindex Bravo impeller is designed to minimize this drop. Higher pumping efficiencies also correlate with lower wear rates. Wear Experience shows that the design of the impeller and volute is as important as the choice of material, in order to minimize the wear rate. The shape of the impeller used in slurry handling is important in ensuring high wear resistance and hydraulic efficiency. When pumping...