Pump resolves maintenance issues

Problem

Mechanical seal failures on 6-inch pumps in lift stations were frustrating Jay Roberts, primary operator at the Bradford (Ohio) Wastewater Treatment Plant. Replacing the proprietary seals took weeks and averaged nearly $3,000 per pump, severely straining the maintenance budget. Roberts wanted a pump that would warn of impending seal problems, be faster and less expensive to repair, and resist clogging.

 

Solution

The village purchased a Barnes 4SHMD 3-inch solids-handling submersible enclosed monovane pump with 25 hp motor from Crane Pumps. Installing it in the Wise Street lift station required a 4- by 6-inch slide rail adapter to fit the old pump’s base elbow, and a MiniCAS adapter relay to connect to the existing control panel.

 

Result

An alarm connection to the plant’s SCADA system warns of seal issues. The lift station is trouble-free. Roberts plans to purchase another 4SHMD pump for another lift station. 937/778-8947; www.cranepumps.com.

 

Pump eliminates debris and drag

Problem

In the hilly topography of Summit County, Ohio, high-strength waste from medical and day care centers, restaurants, and schools often clogged the more than 100 grinder pumps in 108 lift stations sending flows to two wastewater treatment plants. The most problematic stations choked almost daily. The most notorious was the 1.5 mgd Station 10 with three 80 hp pumps rated at 25 to 75 gpm. Incoming flow cascaded down a sloped wall before reaching the pumps in a trench in the floor.

 

Solution

Engineers from ITT Water & Wastewater recommended a test of the Flygt 66 hp N-pump in Station 10. A 4-inch discharge throat, semi-open impeller, and relief groove in the volute streamline passage of material. The impeller blades with flattened, backswept leading edges sweep solids from the center to the perimeter of the inlet. As the impeller turns, rags and other long stringy material are forced into the spiral-shaped relief groove, helping tug material from the impeller into the volute. A guide pin in the volute pushes solids away from the impeller, enabling them to be pumped out. The design also eliminates debris-induced drag.

 

Result

The test was so successful that the utility installed N-pumps in other stations and plans to add more. Eliminating pump drag led to an average 40 percent energy savings. 704/409-9700; www.flygtus.com.

 

Control reduces energy demand

Problem

The Lockport (Ill.) Wastewater Treatment Plant was expanding from 2.3 to 3.4 mgd. Having used technologies from Metropolitan Industries before, city engineers consulted with the company to find additional ways to lower blower energy usage.

 

Solution

Metropolitan recommended controlling dissolved oxygen (DO) in the six aeration basins with a proportional-integral-derivative (PID) control loop that adjusts blower speed. A motor-operated butterfly valve in the zone header pipe balances the airflow between basins and the treatment zone within each basin regardless of differences in water elevation. The SCADA-remote thermal unit holds the adjustable DO set points for several zones using multilevel, cascaded, PID loop strategy that compensates for BOD, air density, blower efficiency, plant flow, and blower surge mitigation.

 

Result

Plant operators are maintaining an efficient, precise, optimal DO concentration at each aeration chamber. A pilot study by Metropolitan Industries showed an average energy savings of 16 percent. 815/886-9200; www.metropolitanind.com.

 

Turbo blower cuts energy costs

Problem

The Little Cedar Bayou Wastewater Treatment Plant in La Porte, Texas, treats about 4 mgd and aerates its basin and tanks with two 25 hp positive displacement blowers. “I figured that it cost a minimum of $6,500 per year to maintain them,” says Billie Brooks, senior operator. The city looked for ways to minimize expenses and improve energy efficiency.

 

Solution

The city purchased a Frame 2 high-speed turbo blower from HSI. The pre-engineered system included compressor, motor, variable-speed motor starter, pressure relief valve, expansion joint, and control cabinet. The HSI blower line is rated at up to 10,000 cfm/25 psi. Each impeller vane configuration matches its own specific volute to optimize aerodynamic efficiency. Impellers at both ends of the shaft counterbalance thrust load in the axial direction to reduce stress or twisting and enhance stability. As the shaft rotates at high speed, the air film formed between it and the bearings achieves friction-free flotation, eliminating the need for lubricants.

The fully enclosed blower does not exceed 85 decibels, and the compact cabinet saves space. No special foundation support is required, and the design offers easy access without overhead cranes. The integrated controls can be upgraded to communicate with all remote operation and monitoring protocols.

 

Result

“The new unit replaced the other two blowers and reduced our maintenance to just changing an air filter,” says Robert Banks, plant supervisor. After one year, the unit lowered annual energy cost by almost 35 percent. Based on those savings, the city should realize payback in two to three years. 800/725-6409; www.hsiblowers.com.

 

Bypass pumps enhance efficiency

Problem

Metro Vancouver was demolishing a 46 mgd concrete sewer interceptor in Coquitlam, B.C., and needed to bypass the vaults between nine manholes, a distance of 2,800 feet. The project managers contacted Rain for Rent for help.

 

Solution

Rain for Rent provided two DV-600c 30- by 24-inch Power Prime pumps as primary units and two DV-400c 18- by 16-inch pumps as backups, joined by dual lines of 24-inch fused HDPE pipe 1,800 feet long. The lines split into three runs of 24-inch pipe for the remaining 1,000 feet to reduce friction loss, head pressure, and flow velocity.

Rated at 28,000 gpm, each primary pump produced 96 feet of head, lifted 28 feet, handled 5.25-inch solids, and ran at 87 percent efficiency, saving substantial fuel. The high-flow capacity of the primary pumps allowed the entire setup to fit in a 170-square-foot footprint under an overpass. The 430-gallon integral fuel tank on the primary pumps provided a 22-hour run time. Rated at 16,000 gpm, each backup pump produced 200 feet of head, lifted 28 feet, handled 4.5-inch solids, and had a 100-gallon fuel tank.

 

Result

The pumps’ compact design and high capacities meant fewer pumps on the small job site. The bypass system pumped nonstop as Rain for Rent personnel monitored the operation. 800/742-7246; www.rainforrent.com.

 

Right-angle speed reducer

Problem

The 35 collector drives for settling tanks at Donald C. Tillman Water Reclamation Plant in Van Nuys, Calif., had maintenance issues that included high-speed-pinion-related failures. Pritpal Jhaj, mechanical supervisor, and Victor De La Rosa of Applied Industrial Technologies in North Hollywood, consulted the engineering department of Sumitomo Drive Technologies.

 

Solution

Sumitomo engineers reviewed the critical dimensions of the double-extended output shafts on the existing gear motors, then selected model LHHJS-3B12DBTK-Y1-956:1 Cyclo Bevel Buddyboxes with cycloidal gear reducers and a single-stage right-angle spiral bevel gearbox in a shaft-mounted design. To eliminate time-consuming motor alignment hassles with the existing motor scoop arrangement, Jhaj and Rosa opted for self-aligning NEMA C-face adapters. They also provided transition bases to adapt the units to the standard foot dimensions.

 

Result

The first six units are in operation, and 20 more are ordered for the next phase of the retrofit. 800/762-9256; www.smcyclo.com.

 

Cake pump system enhances reliability

Problem

The Harpers Ferry and Bolivar (W.Va.) Public Service District Waste Water Treatment Plant used open-air drying beds to dewater biosolids. A front-end loader then dumped the cake into trucks for hauling to a landfill. To comply with regulations mandating more efficient and contained systems, plant supervisor Jimmy Williams ordered a new belt press from Siemens.

 

Solution

Seepex Inc. integrated its progressive cavity pumps into the press to make it more automated. The BN 30-6LT unit conveys material to the press at up to 2,200 gpm/720 psi. A cost-effective direct flange-mounted drive eliminates the drive casing, elastic coupling, and common baseplate. The drive and rotating unit have plug-in connections for easy maintenance.

Cake as high as 16 to 18 percent solids falls into the rectangular feed hopper of the BTI 17-12 pump. When the cake reaches a certain level, the load cell system activates the pump. Capable of 572 gpm/540 psi, the pump adjusts production as needed, loading cake via piping into the trucks. When the belt stops feeding the hopper, the pump shuts off. Load cells, discharge pressure protection, and run-dry (TSE) and motor overheating protection are connected to a custom control system for easy adjustments and monitoring.

 

Result

“The pumps are running without issues and we’re happy with the solution seepex provided,” says Williams. 937/864-7150; www.seepex.com.