New Tube Cleaning System Shoots Down Power Plant Maintenance Costs
Wisconsin Electric's Presque Isle Power Plant in Marquette, MI had some very good reasons to put a new tube cleaning system to the test recently. This 624 mW coal-fired plant on the shore of Lake Superior in Michigan supplies power to much of the region, a precious commodity especially during the extremely cold winter months. The harsh environment, with its extreme climatic fluctuations between summer and winter, puts critical demands on the plant's maintenance department to provide optimal power generating performance.
According to Ms. Sue Sorrelle, the plant's Maintenance Supervisor, keeping the stainless steel tubes in the main condenser units clean is paramount to achieving this performance. Because of the very cold water temperature of Lake Superior, fouling due to mussels and other bio-forms found in warmer waters to the south is not the case here. At the Presque Isle plant the problem is iron oxide, which enters the condenser tubes as very fine particles and builds up over a matter of months into hard, constricting, deposits. Ms. Sorrelle says that because these deposits result in back pressure, which limits the performance of the condensers, regularly scheduled tube cleaning is required to reduce the back pressure and improve performance.
For many years, condenser tube cleaning in the plant was done with a high-pressure hydro-blaster, sending water through a nozzle at up to 6,000 psi. An operator would insert the high-pressure hose eighteen inches into the 7/8" tube and then signal a partner to activate the pressure. After sending the hose down the length of the tube, which could range from 22 feet to 30 feet depending on the unit, it was depressurized, pulled out, put into the next tube and the operation repeated.
According to Ms. Sorrelle, there are some 5,000 tubes in each of the plant's 9 condenser units and hydro-blasting 45,000 tubes was extremely time consuming. On top of that, the first eighteen inches of each tube never really got clean. But, for years, everyone in plant maintenance was under the impression that it was the best way to do the job. "It was the safety factor that was a major concern," says Ms. Sorrelle. "In a repetitive job like hydro-blasting, and working up to a 12-hour shift, an operator's guard could be let down and an accident might happen."
Considering the serious injury that could result from the powerful water jet hitting someone, they looked for a better way. Reviewing the options available in the marketplace, Presque Isle opted for the BFP-3510 Big Shot condenser tube cleaning system from Goodway Technologies Corporation (Stamford, CT).
This newly developed tube cleaning system uses pressurized water (up to 400 psi) to "shoot" projectiles such as coiled brushes or Super Scrubbers through the tube. The operator simply inserts a projectile into a tube and uses the Big Shot's gun to shoot the projectile. As it is propelled forward, the projectile forces out deposits, leaving the tube thoroughly cleaned, according to Ms. Sorrelle.
They also chose to go with the Goodway Super Scrubber tube cleaning projectiles. They come equipped with either high tensile carbon steel or wear resistant polymer blades and resilient nitrile bushings. Each projectile has a force adjustment that is preset at the factory to match both the type of deposit and tube material for tubes ranging from 5/8" to 1 ﾼ" O.D. Presque Isle selected the carbon steel blades to remove the hard iron oxide deposits. These blades are also good against manganese, calcium, carbonate and silica. Plants with soft deposit problems such as mud, algae, silt, and slime, or with softer tube materials may elect to go with the polymer blades. Both types of Super Scrubbers are reportedly effective in removing clams, mussels and barnacles. Each of the reusable projectiles can be shot several times.
Ms. Sorrelle claims excellent tube cleaning results with the new system, as well as elimination of the safety concerns that had prevailed during hydro-blasting.
"We load and shoot six hundred Super Scrubbers at a time," she says, "and it only takes about three seconds for a Super Scrubber to clean a tube. Moreover," she adds, "that's the entire length of the tube, including the first eighteen inches."
A screen is set up to catch the projectiles at the far end of the tubes. They are rinsed off and quickly loaded into the next group of dirty tubes. After all 45,000 tubes have been cleaned, the Super Scrubbers are rinsed, dried and stored for the next time the tubes need to be cleaned.
The time needed to clean the condenser tubes at the Presque Isle plant has been cut from about five days, including setup, down to three-and-a-half. Ms. Sorrelle feels that , because of the extremely thorough cleaning action, the length of time between cleanings may also be extended, from the current twelve months to perhaps eighteen. "Downtime costs money," she says, "so by keeping the units on longer we save dollars and everyone benefits."
She is also planning to increase her Big Shot "ammo" to 1,200 Super Scrubbers and perhaps add a second gun in the future to increase their cleaning capabilities even further.
As for the heavy duty BFP-3510 Big Shot system, the unit comes fully equipped with a 10 hp motor, a triplex plunger two gun pump, water inlet and outlet hoses, and gun, all on a rugged, custom fabricated cart. The unit is compact, with oversize wheels, allowing Ms. Sorrelle's crew to move it quickly and easily to each condenser.
At the Presque Isle Power Plant, the Goodway Big Shot has resolved a major safety issue while providing increased cost savings and operating efficiency.