When Midsouth Aggregates needed to replace a submersible pump that pumped quarry water to a stone washing tower, plant manager Shane Horton knew he also wanted to increase the discharge flow of the pump. The existing pump had a four-inch discharge. The new pumping conditions were 1000 gpm, 50 feet of vertical lift and 500 feet of horizontal run to the water tower. The manufacturer of their existing pump would have to use a pump with an eight-inch discharge in order to meet the new conditions.
Shane Horton wanted to know what other options were available and found the answer with Scott Morrow, sales engineer for Brownlee-Morrow, a dynamic fluids transfer distributor specializing in pumping equipment. Morrow suggested a BJM Pumps submersible built specifically for hard to handle rock slurries. He recommended the BJM KZN220-30 HP high head, hard metal agitator slurry pump with a six-inch discharge. Because of BJM’s wide experience in pumping coal slurries, lime slurries and a variety of abrasive products found in wash down sumps, Midsouth Aggregates decided to give the pump a try. The quality features built into BJM’s KZN slurry pump series were also factors in the decision, such as these two key features:
• The pump provides optimum wear resistance. All wetted parts are constructed of abrasive resistant 28 percent chrome iron (600 Brinell, 71 Rockwell C) for maximum wear life. In addition, a replaceable hardened wear plate is located on the suction side, where erosion would cause a loss of pump performance.
• The pump delivers maximum solids handling capability. An integral agitator fluidizes settled solids into a slurry making them easier to pump with less chance of clogging. The semi-open impeller handles abrasive solid concentrations as high as 70 percent by weight.
Also weighing into the decision was the fact that the KZN slurry pump achieves maximum service life because of numerous design features, including
• Class H motor insulation and built in amperage (FLA) and temperature overload protection;
• Double silicon carbide mechanical seals in a separate oil filled seal chamber;
• Heavy-duty lip seal that provides additional protection for the mechanical seals; and
• Stainless-steel shaft and shaft sleeve that provide maximum wear and corrosion protection.
Pump volutes are cast from hardened ductile iron (300 Brinell hardness), which is twice as abrasive resistant as standard ductile iron with walls that are extra thick at the point where pumped slurry enters the discharge.
Another key part of the pump construction is the semi-open impeller. Also made of 28 percent chrome, the slurry impeller must have the ability to work in tandem with the agitator to pass the aggregate through the pump and out the discharge.
The agitator’s ability to keep solids suspended in the fluid being pumped and keep the suction clear of clogs greatly aids the pumping action.
The existing submersible pump in Midsouth Aggregates’ application was a side-discharge, 90-degree elbow pipe that had a high wear area on the 90-degree turn.
Midsouth Aggregates liked the BJM vertical top discharge feature of the KZN220 agitator pump. This feature promotes optimum wear resistance along the discharge path, as well as use of the fluid being pumped for natural cooling of the pump’s internal motor functions. BJM’s vertical design also allows for the sump to be pumped down to within inches of the bottom.
Further, the vertical discharge and the 22.75-inch diameter of the KZN220 creates a space saving footprint and allows installation in the tightest of manholes.
