37 Repair and maintenance of machines, pumps, rotary pumps, piston pumps, single-phase and multiphase pumps, single-stage and multistage pumps, axial pumps, radial pumps, pumps for conveying liquids, gases, solids and mixtures thereof, pumps for conveying oil, gas, pulp, water, granular solids, mixers, agitators, conveyors; repair and maintenance of installations with machines, pumps, rotary pumps, piston pumps; repair and maintenance of installations with single-phase and multiphase pumps, single-stage and multistage pumps, axial pumps, radial pumps; repair and maintenance of installations with pumps for conveying liquids, gases, solids and mixtures thereof; repair and maintenance of installations with pumps for conveying oil, gas, pulp, water, granular solids; repair and maintenance of installations with mixers, agitators, conveyors