In 2008, as part of its $3.7 billion multi-year Capital Improvement and Replacement Plan to expand capacity to 340 MGD, MSD's LeMay plant installed three new automatic R.P. Adams multiple element strainers. |
In addition, because the backwash mechanism of the automatic basket design comes into close proximity to the straining media, large, suspended solids often encountered with raw water can become lodged between the media and the backwash arm causing strainer media damage and/or rupture. Due to inherent design limitations, under high differential pressure conditions, the basket often becomes deformed, further increasing the risk that the backwash mechanism will come into direct contact with the media and cause damage.
"I know of other facilities that have other types of strainers, and through word of mouth we've learned that there's a lot of labor involved with them," says Winslow. "But our multi-element water strainers from R.P. Adams are pretty much maintenance free. They just do their thing and demand very little attention – it's what every plant operator expects in critical process equipment."
Multi-element, automatic, self-cleaning strainers were first introduced and patented by R.P. Adams in the 1960s, and are now incorporated in over 10,000 installations worldwide. These automatic self-cleaning strainers employ a multi-element, cylindrical wedge-wire design whose tubular elements provide 3-4 times the straining surface area of a typical automatic single basket strainer.
"Each tube is relatively small, but because of the high number of them they have the largest open surface area of any strainer," says Ted Gast, a chemist and general manager at Carl F. Gast Co., a St. Louis manufacturer's representative for industrial instruments and equipment serving customers in Missouri and the adjacent five-state area.
"With the way these strainers are designed, they can operate in a 2-4 PSID range," explains Gast. "The clean differential pressure is maintained until 75% of the open straining area is plugged. Then the differential pressure begins to rise until the backwash set point is reached and the cleaning cycle is initiated. Maintaining a 2 PSID pressure drop over most of the filtration cycle means reduced power consumption from feed pumps which adds up to significant long term savings"
