Strong Acids and Bases are No Problem at this Wastewater Plant
Since 1980, Polaroid has employed gear pumps to handle caustic and sulfuric acid, used to adjust pH in the company's wastewater system. The first pumps were mechanical seal units, supplied by Liquiflo Equipment Co. (Garwood, NJ), through Pump Services Corp. (Stoneham, MA). In 1985 Polaroid installed a new, state-of-the-art wastewater system, and fitted the system with Liquiflo gear pumps (37 and 312 Series) and centrifugal pumps (62 Series) for chemical handling.
The 37 (10 gpm) and 62 Series pumps were all magnetic-drive units, but since the heavy-duty 312 (27 gpm) Series gear pump was not available as a mag drive, four units with mechanical seals were installed. The gear pump's motors were attached to frequency controllers so that accurate metering could take place.
Over the next five years the mag drive pumps performed to specification. Polaroid supervisors were especially pleased with the labor savings, as no mechanical seal maintenance is required for sealless pumps. With no seals, the operating area around the pumps stayed free of acid spills-cleaner and safer for operators and maintenance personnel. In 1990 Liquiflo released its 312 Series gear pumps in a mag drive version, and Polaroid immediately installed one. The pump ran for seven years with only routine maintenance. Just one set of bearings needing replacement.
In 1997 the Polaroid wastewater plant was updated. At that time, the three 312 Series sealed pumps were replaced with the sealless, mag drive version. Polaroid's wastewater area now uses only Liquiflo mag drive pumps for its chemical handling needs. Since sealed and mag drive pumps of the same size have the same dimensions, the new pumps fitted in line perfectly, with no adaptation required.
The three new pumps are made of Hastelloy C, with Hastelloy/Teflon gears and Teflon bearings. Some of the pumps handle sulfuric acid. Other pumps in the series handle caustic. Hastelloy materials are not required for the caustic service, but Polaroid engineers wanted all the pumps the same for complete interchangeability and reduced parts inventory. The Polaroid wastewater plant runs 24 h/d. The pumps are in operation during that time, injecting sulfuric acid or caustic as required to correct pH of the wastewater.
Pump Services Corp., a Liquiflo sales representative headquartered in Stoneham, MA, supplied all the Liquiflo pumps and parts. Pump Services' Scott Round was involved with the sales to Polaroid. Round says, "The customer is very happy" with the mag drive pumps. But, he notes with a smile, "We aren't because the long life of the pumps means that parts sales are minimal!"
About the mag drive pumps
Liquiflo's sealless, magnetically coupled gear pumps are an industry standard for low to moderate flows of difficult or toxic chemicals. The Rotogear pumps offer smooth, pulseless flow and low NPSH requirements. Magnetic coupling design is a major contributor to the pumps' long life in rigorous service. No seals are needed because the fluid end of the equipment is isolated in its own can, with no chance of leakage reaching either the drive end or the atmosphere.
In the Liquiflo magnetic drive pumps, radially gapped, permanent magnets are mounted on two cylinders. One cylinder is attached to the motor shaft, the other to the drive shaft. As the motor turns, the outer drive magnet turns along with it. It rotates the inner magnets and, with them, the gears. A can and O-ring seal the pump between the two magnetic cylinders. The magnets are oversized to ensure a high level of torque transmission.
For more information: Liquiflo Equipment Co., 443 North Avenue, Garwood, NJ 07027. Tel: 908-518-0666, fax: 908-518-1847.