McLanahan’s M3H range of Pumps were developed from more than 50 years of Pump experience featuring head and efficiency improvements from previous models. This range of horizontal spindle, abrasion/corrosion resistant centrifugal Slurry Pumps is designed for construction sands, frac sand, glass sand, silica sand, mineral sands, water treatment facilities and more.
Why McLanahan Slurry Pumps
McLanahan Slurry Pumps feature a split casing design to allow easy access to the liners, the impeller and the gland for maintenance. Most Slurry Pumps come with an assembly aid arm to support the suction casing during impeller replacement and gland maintenance. This feature allows the technician to swing the casing away from the Pump instead of dropping the component to the ground or using a crane.
McLanahan Slurry Pumps feature field replaceable wet-end liners to facilitate an ease of maintenance. These liners are self-gasketing to provide a reliable seal. Several compounds of rubber are available for various duties: a natural rubber blend for high abrasion resistance, and nitrile and neoprene for different chemistries.
Three styles of gland are available with McLanahan Slurry Pumps:
- D-Type glands are our most fitted gland and feature a rotating rubber seal ring and a static ceramic face. These two highly abrasion resistant components are adjusted such that a minimal amount of slurry is allowed to pass through between the surfaces to act as lubrication. This gland design absorbs little energy and requires no external lubrication; although in some cases it can be fitted with flushing water. This design is ideal for applications where clean process water is unavailable or dilution of the slurry being pumped is undesirable. This design is not recommended for more viscous types of slurry.
- H-Type glands have the lowest maintenance needs but require a reliable consistent fresh water supply of 1-5gpm at 3-5psi above pump discharge pressure (0.2-1 m3/hr at 20-25 kPa above). This gland features two rubber seals separated by a lantern ring where the pressurized water is injected. The outer seal is adjusted to allow gland water to seep out for lubrication, while the water at the internal seal flushes solids away from the seal. This gland is ideal for applications such as Thickener underflow.
- P-Type glands are the classic design and are the most common in the industry. Specialized packing rings are wrapped around the gland sleeve and compressed to make a seal. This gland requires an external water source to lubricate the packing and will leak small amounts of process water to atmosphere. Clean water is most critical to this gland, although in some cases a grease lubricated gland can be supplied with hydrocarbon-compatible liners and components.
Open vane impellers are not a recessed impeller style Pump. They are the standard Pump head with a vortex flow design impeller that impels fluids through and out of the casing. Open vane is the choice for solid and fibrous material with a minimal risk of clogging, such as in agricultural applications separating manure from bedding sand.
McLanahan's bearing assembly is exceptionally simple but nonetheless long-lasting. Unlike other manufacturers, the bearing housing reassembly process requires no preload setup given the wet-end, heavy-duty roller bearing and the drive-end, double-row, self-aligning, spherical roller bearing. Fit the components into the housing per the Installation, Operation and Maintenance Manual, lubricate as instructed and you are ready to go. Factory rebuilt bearing assemblies are available for the most urgent of maintenance.
How Slurry Pumps Work
Using the conversion of rotational kinetic energy into the hydrodynamic energy of the fluid flow, centrifugal Slurry Pumps motivate fluid flow along pipelines. Pump rotation, and thus rotational energy, is typically created by the electric motor driving the Pump shaft through a V-belt drive. The fluid enters axially into the eye of the Pump impeller, which by its rotation acts tangentially and radially on the fluid. The fluid is accelerated by the impeller gaining velocity and pressure, flowing radially outward into the casing, decelerating but building pressure. Being pressurized, it then exits the volute. The displaced fluid in the Pump head is replaced by atmospheric pressure and static pressure acting on the fluid in the sump, pushing it into the impeller.
The speed of the Pump is regulated by the ratio of the transmission plus, in some cases, the use of a variable frequency drive to tune the speed for a more exact duty. Care needs to be taken not to use high turn-down ratios, which result in the loss of power. Head or more specifically total dynamic head, which is the sum of static, friction and pressure heads, is used to find the speed head. Calculated water head is corrected (HR) using the d50 of the particles being pumped, the percent solids by volume. Horsepower is calculated as work done and thus includes the fluid specific gravity. Reference should always be made to the manufacturer’s curves to ensure the Pump is operating in the most efficient zone.
It should be noted that this design of Pump, unlike a self-priming positive displacement Pump, does not actually suck the fluid into the casing. As discussed above, the fluid flows into the Pump based on atmospheric pressure and the height of fluid in the vessel (14.5 psi or 33.5ft.hd. [10mhd] + the height to water level in the Sump).
Other factors affect the performance of the Pump, most important of which is the Net Positive Suction Head (NPSH), which is not only an equipment issue but a system issue. NPSHA is a measure of how close to vapor pressure the fluid becomes. NPSHR is head value on the suction side that is required to keep the fluid from cavitating. Heated solutions are particularly prone. Significant damage can occur to the impeller and bearings when a Pump is cavitating.
The reverse function of the centrifugal Pump is as a water turbine converting potential energy of water pressure into mechanical rotational energy. Examples of this are in tailings disposal down long inclines to ponds. Special builds are required.
Lining materials vary and are typically selected based on the materials to be handled and any chemistry present. Most sand sized materials <5mm (4mesh) can be handled effectively by the use of the high-quality natural rubber compound liners. Gravel should be handled by hard metal Pumps, such as Ni-Hard or Hi-Chrome (27%).