Chemical Manufacturer Reduces Maintenance Costs by Switching to Submersible Slurry Pumps

When a pump needs to be pulled from service, the maintenance manager often needs to make the decision to either have the pump rebuilt or to replace the pump entirely. Money is often the biggest motivator when it comes to making that choice. Maintenance dollars only go so far, and when older pumps are involved, the cost to rebuild can be higher due to the difficulty of sourcing some of those replacement parts. When one chemical manufacturer pulled their sump pump, they made the decision to replace rather than rebuild. Chemtrade Logistics Inc. provides several types of chemicals to industrial companies around the globe. One of their production facilities in Virginia manufactures alum. Alum, which is also known as aluminum sulphate, is used for wastewater treatment, pulp and paper, and industrial processing applications. The chemical manufacturing plant worked with their service provider to select a pump that would allow them to reduce maintenance costs and improve pump reliability.

The chemical manufacturing plant’s central drainage sump relied on an old vertical pump to pump slurry that was collected in the sump. The sump collected rain water and water from the plant’s mud wash process. The mud wash process involves setting a filter press to press water out of the mud so that the remaining “cake” can then be processed for proper disposal. In addition to the stormwater and water from the mud-wash process, the sump also collected the wash down water. When the process area was washed down, bauxite (the principle ore of aluminum) would also get washed into the sump, creating a thick slurry that frequently clogged the vertical pump. In April 2015, the chemical manufacturing plant’s maintenance team was pulling the vertical pump out of the sump. “The vertical pump had to be at least 25 years old, and the bottom bearing was completely worn out,” said Arthur Grammer, the chemical plant’s maintenance manager. “Instead of trying to find parts to piece the thing back together, I figured it might be more cost effective to just replace the pump. We were tired of pulling that pump, the repairs were expensive, and we wanted something that was more reliable.” The solution was a new submersible slurry pump. In previous years, he had helped the maintenance team select other stainless steel submersible pumps from the same pump manufacturer, which had been installed in other applications at the chemical manufacturing plant. For this specific application, the particular submersible slurry pump was chosen because it included several desirable features:

Chrome Iron Agitator to Suspend Solids

Made from abrasive resistant 28 percent chrome iron, the agitator in the pump makes it an ideal solution for handling the bauxite slurry. The bauxite is comprised of a mixture of aluminum hydroxides, clay minerals and other insoluble materials, so it was critical to have the high-chrome agitator suspend the solids in the slurry and allow the pump to transport the slurry to the recovery process.

Chrome Iron Semi-Open Impeller to Pass Particulate

The pump is engineered with a semi-open impeller and has been proven to handle slurries with solids concentrations as high as 70 percent by weight.

Chrome Iron Wear Plate to Resist Erosion

The pump included a replaceable 28 percent chrome iron wear plate, which makes it erosion-resistant. Erosion on the suction side can reduce pump performance, so the hard iron replaceable wear plate helps to increase overall pump life.

Durable Construction for Industrial Applications

The pump includes a stainless steel shaft and shaft sleeve, which reduces shaft wear from abrasive slurries. The pump volutes are cast from hardened ductile iron, which—at 300 Brinnell hardness—are twice as resistant to abrasives as standard ductile iron. The hardened ductile iron volutes are cast with extra thick walls at the point where the pumped slurry enters the discharge.

Motor Protection for Reliable Operation

The pump is protected by double silicon carbide mechanical seals that are housed in a separate oil-filled seal chamber, and the heavy duty lip seal offers additional protection for the mechanical seals. The motor is further protected with Class H motor insulation, built-in amperage (FLA) and temperature overload protection.

Slim, Top Discharge Design

With a slim, top discharge design, the pump is cooled by the pumped liquid and can pump a sump pit down to within inches of the bottom. A side discharge pump without a cooling jacket must stay submerged to avoid overheating, leaving as much as 3 feet of un-pumped slurry. The pump would be perfect for the 4-foot deep central drainage sump. After reviewing all the features of the pump, the team worked to process a “management of change” (MOC) through its corporate office. If equipment needs to be changed out in the manufacturing plant, and the replacement is not identical to the original equipment, then an MOC is required and reviewed by the engineering department to prove that the new equipment will work in the entire system. The MOC must include the exact specifications and outline the projected cost savings. It was a cost reduction in this case. To get the new submersible pump was less expensive than repairing the obsolete vertical pump. Chemtrade’s careful evaluation concluded in June of 2015. One pump was installed in the central drainage sump along with a moisture detection system. This system includes a sensor probe inside the oil chamber that can provide an early warning to protect the pump motor. When the moisture detection circuit is properly connected to a control panel, it informs the pump operator that there is moisture within the oil chamber, giving them an opportunity to inspect the pump and take preventive measures. “The pump has done extremely well so far. It handles solids well, just as advertised. Three months after the pump was installed, it pumped 32,000 pounds of bauxite slurry over a period of three days. It was truly impressive. Needless to say, we’re very satisfied,” said Grammer. “Moving to the new pump has benefited us with noise reduction in the process area, improved fluid handling, reduced our repair costs and freed up our maintenance team to work on other plant projects.”