Metal-finishing company deals with noisy, poorly controlled pumps

June 1, 2015

Hardened pump meets challenge, where others feared to tread

A major Ohio-based metal-finishing company operates in a joint venture with a U.S. steel company and a Canadian-based holding company that includes that includes 40 other companies.

They are all in the business of electroplating, high-tolerance parts and assemblies machining and development of new finishes for steel-work rolls used in steel and aluminum rolling mills.

The company has seven locations in the United States. Its 50,000 square-foot plant in Ohio employs about 50 people. Operations involve grinding, machining and plating of metal in the refurbishment of process rollers, to provide superior finishes on sheets of steel and aluminum.

Cooling bath water

Like many metal-finishing operations, the plant flows a cooling bath — mostly water — over the cutting elements during the machining of steel rollers. Large amounts of metal shavings called grinding fines end up in solution as the coolant washes over the cutting surface. These fines must be removed in order to reclaim and reuse the fluid. Spent coolant is channeled from several work areas into a 250-to-300-gallon catch sump, from which the company had used diaphragm pumps to move the coolant to a filter for fluid reclamation.

Because of the need to keep the coolant moving through the filter at a constant pace, with the grinding fines always in suspension, it is important that the sump maintain a constant three-foot fluid level.

The company had varied the air supply to the diaphragm pump to adjust the flow of fluid and maintain the sump’s level, but the pumps were noisy and difficult to regulate. Furthermore, the grinding fines were tearing the pumps apart, and the company was replacing pumps every four to six months — a costly situation for a relatively small plant.

The environment was so hostile to pumps that several pump makers or distributors to even submit a quote for replacement pumps.

Recessed-vortex impulsion

BJM Pumps on the other hand was eager to tackle the challenging situation. The pump it recommended is a 3-horsepower recessed-vortex impeller pump meant especially for solids-heavy sewage and industrial uses. The pump has silicon-carbide mechanical seals and optional proprietary-design inverter-duty motor with special "R"-class insulation.

To further protect the pump from the destructive grinding fines, BJM Pumps worked with its distributor, Atlas Supply, to harden the impeller with a special coating.

The pump is combined with the plant’s existing variable-frequency drive (VFD), and an ultrasonic level control connected to the VFD adjusts the pump’s line frequency to maintain the constant three-foot level in the sump.

A VFD is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage

Further, BJM engineers mapped out the system’s performance curve at various operating speeds, and based on this information, a "T" was added to the discharge line. Half of the fluid is now sent to the filter while the other half is recirculated within the sump for optimum hydraulic performance. It also agitates the liquid, keeping the metal fines in suspension.

While the pump’s line frequency normally ranges from 45 Hz to 50 Hz, the installed motor has the ability to go outside this range when required.

As installed

Atlas Supply, provided a mechanism to control the motor’s speed, which starts at 3,600 RPM but must slow down by as much as 15 percent under heavy load to match the flow capacity of the filter.

The installed system has been pumping approximately 100 gallons per minute for several years now. The pump has been rebuilt only once, and the solution, based on engineering and a strong distribution network, brought the metal finishing’s plant frequent and expensive replacement of its pumps and filters to a complete halt.

BJM Pumps® is headquartered in Old Saybrook, Connecticut, and in business since 1983. BJM Pumps has grown quickly by supplying quality pumps at a modest price.  BJM Pumps serves many different industries through two separate divisions, the first for submersible pumps in the municipal, chemical, construction, sewage, mining and process industries; and the other for electrical motor testers used worldwide in virtually all types of industry and government agencies.

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