Drives and hydraulic aggregates with bypass filter and/or cooler are also used in explosive areas in machine construction or raw material production. The advantage of these circuits is that they create stable and therefore more predictable operating conditions for both the filtration and cooling. Circulating oil in these circuits requires efficient and preferably silent circulation pumps which provide a constant flow rate at moderate pressures. Internal gear pumps have proved especially useful for these applications. They offer compact integration, are relatively insusceptible to particle contamination and have a long life. BFP ATEX 2GD series gerotor motor/pump units are suitable for use in explosive zones 1 (gas) and 21 (dust) and temperature class 4.