Delfluent Services is a consortium of specialized companies based in The Hague that operate wastewater treatment facilities. One of these facilities, the wastewater treatment plant in Houtrust, covers an area of 5 hectares and can treat an average of almost 79,000 cubic meters of wastewater per day.

Treatment begins with the removal of coarse, solid material. The wastewater then passes through primary clarifiers, activated sludge, biological treatment and secondary clarifiers.

The wastewater treatment plant was built in 1967 and had to be modernized in accordance with the applicable environmental regulations. Part of the maintenance project was the replacement of a gearbox that drives the chain wheel in one of the sedimentation tanks. The original gearbox had always required a lot of maintenance and required the basin to be emptied twice a year to carry out maintenance work. This routine maintenance led to production downtime and high maintenance costs. Delfluent therefore decided to use the modernization to convert the system to a maintenance-friendly solution.

Continuous operation under water

The previous supplier had developed a design with a fully submerged, single-stage bevel gearbox. The gearbox was connected to the rest of the drive train above the water level via a connecting pipe. The tube was connected to a pre-stage gearbox and an overload clutch. The application was driven by a 0.55 kW motor. To replace the existing motors and gearboxes, Delfluent turned to Bauer Gear Motor, part of Altra Industrial Motion Corporation.

Bauer has made a name for itself with the development of geared motors for demanding conditions. In particular, the company manufactures motors with protection class IP68, which are waterproof, dustproof and fully submersible.

To ensure the best possible service, Bauer carried out the exchange via its partner Vos Gekas & Boot (VGB), an expert in rotating machinery, including pumps, who already knew the water treatment plant to be modernized very well.

The BK series bevel geared motor can be operated continuously under water. © Bauer Gear Motor

The solution consisted of a drive in the form of a bevel geared motor from the BK series (type BK70G20X-82W/DHEU09SA4/SP), which can be operated continuously under water. This motor series includes models in the power range 0.03 to 75 kW with a mains connection of 110 to 690 V and 50/60 Hz.

Technical simplification makes maintenance easier

Bauer switched from two single-stage gearboxes to a multi-stage geared motor. The bevel gearbox can withstand torques from 80 to 18,500 Nm and ratios from 3.67 to 108.60 in a two-stage version or 7.29 to 441.3 with three stages. In this way, the technical system has been simplified, making future maintenance easier.

By eliminating the gearbox, connecting tube and coupling, the vibrations in the system and its energy consumption could be reduced. In addition to the high protection class, particular advantages of the BK series include simple and cost-effective installation, high energy efficiency, durability and longevity, ease of maintenance and low operating costs.

This specific application runs at a fixed speed, so there was no need for an inverter, which can prove advantageous in other situations. A small 0.37 kW motor with efficiency class IE2 operated directly on line (DOL) offered the most energy-efficient and cost-effective solution.