We had an enquiry from a customer on a drilling rig where the top-drive encoder needed to be explosion-proof and give true absolute multi-turn position, not just single-turn. The Hengstler ACURO AX70 (part of the AX70/71 family) is built for exactly this kind of oil-and-gas hazardous-area duty.
This looks simple, but “explosion-proof” here is a specific enclosure design – the AX70 uses Hengstler’s explosion-proof enclosure “D” in an aluminium housing (the AX71 is the same design in stainless steel, for harsher corrosion environments), ATEX and IECEx certified for hazardous areas. It’s an optical absolute encoder with true multi-turn (not battery-backed), using a 70 mm servo-mount 3-hole face with a 10 mm shaft.
In actual application, the AX70 gives up to 22-bit single-turn plus 12-bit true multi-turn resolution, runs on BiSS, SSI, Profibus, DeviceNet, CANopen or CANLayer2 interface, handles up to 10,000 rpm, and is rated IP64/IP67. Operating range is -40°C to +60°C (narrower than the AX65’s range, since this is an optical rather than magnetic sensor). It’s commonly specified for oil and gas equipment – top drives, drawworks drums, iron roughnecks, mud pumps, catwalks, pipe handling and cranes – as well as food and beverage applications.
From our experience, before we quote this, we would normally check whether you need the aluminium (AX70) or stainless steel (AX71) housing, which interface your controller expects, and the hazardous area zone/gas group classification required. Hope this helps.
