Low Speed Aerators
MAK Water represents US-based mechanical engineering company DBS Manufacturing http://www.dbsmfg.com in Australia. DBS has over 40 years of experience in design and manufacturing of a full line of OEM clarifier and thickener drive units, direct “bolt-in” retrofit drives, low speed mechanical aerators, industrial mixers and rotary distributor mechanisms for the water and wastewater industry.
The NSA-series Low Speed Aerators designed and manufactured by DBS, are available as floating aerators or bridge-mounted units. As such NSA aerators are suited for Oxidation Ditch, IDEA/IDAL and other activated sludge processes, as well as lagoon-based systems.
The NSA aerator uses a planetary gearbox to drive the aerator impeller or rotor. This mass-produced gearbox offers an excellent power/cost ratio. The gearbox is uniquely mounted directly in the aerator rotor, which provides a number of benefits:
- The gearbox operates partially submerged. Water flowing through the rotor cools the gearbox to near ambient temperature, allowing longer oil life.
- The gearbox directly drives the rotor preventing inherent driveshaft vibration problems that are common in traditional low speed aerators that use a double reduction parallel shaft (DRPS) gearbox.
- The gearbox and rotor assembly is attached to a “torque tube” which flexes laterally to dampen shocks caused by wave impact on the rotor.
As standard the NSA aerator features a traditional high-efficiency backwards curved radial blade rotor, which offers Standard Aeration Efficiency (SAE) of 2.1 kgO2/kWh. The NSA aerator is also available with unique Dynamic Draft Tube (DDT) rotor developed by DBS for deep tank applications (6 – 9m water depth) where a draft tube would be required.
The NSA aerator is specifically designed for efficient long-life aeration service. Mechanical features include:
All gears are conservatively rated to provide a large margin of safety. Gears are manufactured from AISI 8620 steel or equal. Gears are finish machined to AGMA 8 quality and hardened to 54-60 Rc.
All bearings are designed to provide a minimum service factor of 3.0. Bearings are of the taper roller or roller type. All gear shafts are supported by roller bearings. All bearings are conservatively chosen to provide a L-10 life of 125,000 hours.
The output drive assembly is of the “dry well” design to prevent gearbox oil from escaping from the gearbox housing. The drive employs splash oil lubrication. Gears and bearings operate partially or fully submerged in the gearbox oil.
Housing is made from cast steel or cast iron, and fitted with a low oil switch (if required).
Motor is a Mill & Chemical Duty Premium Efficiency TEFC electric motor with anti-condensate space heaters. Rating is NEMA Design B, continuous duty at 40 °C ambient temperature; class F insulation. Motor is suitable for use on Variable Frequency Drives per NEMA MG.1 Part 18.104.22.168.
Several material options are available for carpentry of floating aerators including hot dipped galvanised ASTM A36 steel, 304 and 316 stainless steel. The gearbox immersion surface is coated with immersion duty coating system. The center spool surface and the motor are coated with primer and final coat for hostile environment protection.