Issue link: https://www.e-digitaleditions.com/i/1325722
48 / January 2021 powderbulk.com Case history | New elbows fix pneumatic conveying lines PBE A water reclamation plant switched the elbow joints in its pneumatic conveying lines to prevent messy, dangerous blowouts. T he Upper Occoquan Water Reclamation Plant in Centre ville, VA, reclaims more than 30 million gallons of water per day, providing a source of pota ble water for a population of more than 300,000 across portions of Fairfax and Prince William Coun ties. The plant's chemical treatment system uses a steady supply of pebble lime to raise pH levels to a point where phosphorus can be removed. The lime is pneumati cally conveyed to six indoor silos during off loading to adequately supply the treatment plant. Due to high conveying velocities and the pebble lime's 3 to 4 percent grit content, the pneumatic convey ing line's elbow walls experienced frequent failures. During a failure, the plant's workers needed to clean up pebble lime spillage and dust that escaped from a failed elbow. Even a small hole in an elbow would spray abrasive powder into the building, presenting a slipand fall risk and threatening indoor air quality. The required system shut down to clean up the lime and mit igate risks to workers also put the plant behind schedule. Inspecting elbows became a fre quent task, and maintenance per sonnel became experts at replacing elbows to keep the silos in service. Meanwhile, operations personnel were being diverted from their formal responsibilities to help with the cleanups. "It's very difficult for us to replace an elbow," says Robert For gione, director of the operations and maintenance division for the Upper Occoquan Service Author ity (UOSA). "The elbows at ground level aren't easily accessed and the ones on top of the silos are four sto ries up. It's a safety concern as well as a cost concern." With elbow failures occurring approximately every 6 months, For gione needed to find a more perma nent fix for the problem. Pneumati cally conveying high volumes of the abrasive material proved difficult The Upper Occoquan Water Reclamation Plant supplies more than 30 million gallons of potable water per day. The water treatment process requires the use of pebble lime, a highly abrasive material, to raise the water's pH level.