New Generation of Equipment Controls "Ragging" and Improves Performance
The Old Guard
From 1985 until the 1993 expansion, sludge transfer at Rockfish Creek was handled by two older Moyno, Inc.progressing cavity pumps operating at 300 gpm. Although pleased with their performance, plant personnel were becoming increasingly frustrated by recurring downtime due to "ragging" in other pieces of process equipment. "Entrained solids such as rags and other stringy debris were passing right through our macerator, clogging valves and causing pressure fluctuations in our machinery," reports Jimmy Duke, Rockfish Creek's maintenance supervisor. "It was at the time we decided to install a Moyno® Pipeliner grinder to see if it would solve our ragging problems."
After three months, the plant's process equipment was disassembled and checked for build-up. Upon examination, there was no evidence of ragging whatsoever. Plant personnel assumed something was wrong and resumed operation of the Pipeliner. After a period of time, it was checked once more – still no ragging. "Unlike the old ringer washer-type macerator, nothing can escape the Pipeliner." Notes Duke. The Pipeliner's spring-loaded headstock assembly maintains constant force against a shearplate. As strings and other debris pass through the holes of the shearplate, they are reduced to small bits by the headstock's cutter. Larger solids are pushed to the holes where they are chipped and hammered into small enough pieces for eventually passage downstream.
The Next Generation
When it came time for the '93 expansion, Rockfish Creek personnel were ready for a change. The macerator wasn't user-friendly and needed to be shipped out for frequent repair. The piston pumps that sent the thickened sludge to their filter plate press weren't capable of providing high enough flows to feed the press. Therefore the decision was made to request that the engineering firm, Black & Veatch, specify all new Moyno progressing cavity pumps and Pipeliner grinders. "Our experience with the two older Moynos and the Pipeliner was very positive," Duke points out. "The choice was clear."
Rockfish Creek now has 10 Moyno® 2000 progressing cavity pumps as part of its sludge transfer operation. Three operate on a 24-hour, continuous-duty cycle as waste-activated sludge pumps moving clarifier waste to the aerobic digesters. The cycle calls for one hour of run time and two hour's of downtime. The next three are sludge pumps pulling from the primary digesters to feed two, 3 meter gravity belt thickeners. Then three more Moyno 2000 pumps move thickened sludge (4 – 4 ½% solids) from hoppers to holding tanks. Finally, the tenth pump is dedicated to filling tankers trucks for a land application program.
The Moyno 2000 pumps are sealed using a standard 6-ring box with a regulated water-flush system. RKL® Series W pressure sensors in the suction and discharge piping of each pump warn of low pressure and zero-flow conditions. The pumps also feature a sealed gear-type universal joint for long life and reliable performance.
Seven of Rockfish Creek's 10 Moyno Pipeliner grinders are placed in the suction lines before the Moyno pumps and provide an effective solution to the problems of ragging and line blockages. The remaining three serve to condition scum from wet wells transferred by a series of centrifugal pumps. "Our Pipelines have greatly minimized downtime," states Duke. Thanks to the superior performance of the Pipeliners and the ruggedness of the Moyno pumps themselves, Rockfish Creek technicians have only had to replace one stator on one of the pumps since the system was installed in '93.
The Heart of a Progressive Cavity Pump
The key components of the Moyno progressive cavity pump are the rotor and stator. The rotor is an external helix or helices, precision machined from high-strength steel. The stator is an internal helix permanently bonded within an alloy steel tube and made from a tough, abrasion-resistant elastomer, machined fluoropolymer or machined stainless steel. The stator always has one more helix than the rotor to facilitate the progressing cavity pumping action. As the rotor turns within the stator, cavities are formed which progress from the suction to the discharge end of the pump, conveying the pumped material. The continuous seal between the rotor and the stator helices keeps the fluid moving steadily at a fixed flow rate proportional to the pump's rotational speed.
Moyno manufactures all of its rotors and stators in-house using proprietary manufacturing methods refined from over 60 years of experience. As a result, Moyno rotors and stators operate at peak machanical efficiencies for maximum performance and extended pump life.
"An Ounce of Prevention..."
"A comprehensive preventive maintenance plan keeps all of our Moyno pumps and grinders running at peak performance," Duke proudly reports. "We perform daily, weekly and monthly check of all our equipment – everything from temperature and packing leakage, to belt alignment and couplings."
In addition to regular preventive maintenance, Duke credits a well-engineered plant and the technical expertise of his staff for the successful operation of the Rockfish Creek equipment. Moyno-sponsored, hands-on training on proper pump operation and maintenance gives Rockfish Creek technicians the expertise to keep their equipment functioning at peak efficiencies. "The Moyno pumps' reliability and consistent performance, along with our stringent preventive maintenance program has definitely helped us save money in our maintenance budget," Duke says.
Moyno, Inc.