Rotodynamic (Centrifugal) Slurry Pumps

12.0 Scope

This Standard is for rotodynamic (centrifugal), singlestage, overhung impeller slurry pumps, horizontal and vertical of industrial types, herein referred to as slurry pumps. It includes types and nomenclature; definitions; design and application; and installation, operation, and maintenance.

12.1 Objective

This standard is intended to clearly outline information necessary to define, select, apply, operate, and maintain slurry pumps.

12.1.1 Introduction

This Standard covers slurry pumps used for pumping and/or transporting mixtures of solids and liquids or so-called slurries. Slurries are abrasive and if not taken into account, abrasive slurries may cause high wear and shortened life of pumps. Unlike clear water, slurries alter the performance of the pumps and cause wear to the wet-end parts. Below a certain velocity, some slurries also settle out in the piping causing blockages. These differences are such that if they are not taken into account, the pumps will not work satisfactorily or not at all. For this reason, this Standard includes information about slurries and their effects, necessary to select, apply, operate, and maintain different designs and materials of construction for slurry pumps.

12.1.2 Pump types and nomenclature

Figure 12.1 shows classifications of slurry pumps based on mechanical configuration. Figures 12.3 through 12.10B show typical constructions commonly used for each pump type. Uppercase letter designations are for different manufacturer variants of the same type. Other variations are also acceptable.

While there are no rigid rules about where different mechanical configurations are to be applied, initial cost, wear parts (maintenance) cost, and arrangementconvenience are such that mechanical configurations tend to be aligned to certain services.

The separately coupled, frame-mounted mechanical configurations are preferred for the heavier solids transport wear services described later in Section 12.3.4.2. The hard metal pumps are preferred for services involving the largest sizes of solids. Elastomer pumps, by virtue of the needed support, must be of the lined type.

Cantilevered wet pit pumps are used in plant mining process service but are more widely used in the lighter class wear services for cleanup and lower concentration slurries. These pumps usually are limited to no more than 300-mm (12-in.) discharge size.

The close-coupled submersible pump types are similar to the cantilevered wet pit pumps, mostly employed on clean-up services, but there may be areas where they are used as process pumps. These are also limited to smaller sizes.

12.1.3 Definition of slurry

Slurry is a mixture of solids (specific gravity greater than 1) in a liquid carrier, usually water. It is often used as a means to transport solids. Slurries also occur when solids are present as an incidental part of the process. The properties of the solids and liquid as well as the amount of solids are variable. The solids size may vary from a few micrometers, often referred to as microns, up to hundreds of millimeters and the solids may settle below a certain transport velocity. The properties of slurry, therefore, are highly variable. Slurry may behave like a Newtonian or non-Newtonian fluid.

It may be abrasive and/or corrosive depending on the composition. Slurry pumps are usually employed to move slurries with solids concentrations between 2% and 50% by volume and specific gravities of the slurry up to 5.3. Slurries with solids of wood, paper, and other organic materials also exist but are not covered by this document.

12.1.4 Definition of slurry pumps

A slurry pump here is defined as a pump suitable for pumping a liquid containing abrasive particles. Slurry pumps vary in construction depending upon the properties of the slurry to be pumped; they are generally more robust than the pumps used in clean-liquid services, and they often have replaceable wear parts. Figure 12.2 shows how various materials are typically used in slurry pumps. The maximum pressures noted are for one or more single-stage pumps, operating in series, at one location. The maximum permissible head per stage is shown in Table 12.6 located in Section 12.3.5 of this document.

12.1.5 Overhung impeller

The impeller is mounted on the end of a shaft, which is cantilevered or “overhung” from its bearing supports.

12.1.6 Frame mounted

In this group, the casing and impeller are mounted on a bearing frame that is separately coupled (not part of the driver). The frame may provide total support for the entire pump or the casing may also have feet for additional support.

12.1.7 Cantilevered wet pit

The impeller is overhung and the shaft is oriented vertically. The bearing housing is mounted above a pit.

12.1.8 Submersible

A close-coupled, overhung design, with a submersible motor. In service, these pumps are normally submerged in the pumped fluid.

12.1.9 Lined type

These designs incorporate field replaceable and permanently bonded liners. Field replaceable liners are commonly elastomers or wear-resistant metals located in critical high wear areas. Designs that utilize a permanently bonded layer, such as rubber vulcanized to a metal casing, are also included in this type.

12.1.10 Unlined type

A conventional, radially split, overhung design with a single wall (unlined) casing. It may include the addition of wear plates or sideliners.