FLENDER ATEX-Certified Couplings for Explosion Protection

FLENDER ATEX couplings are industrial shaft couplings from Flender that are certified for use in potentially explosive atmospheres. Flender states that a large proportion of its couplings have been ATEX certified for decades, under Directive 2014/34/EU, which replaced Directive 94/9/EC in April 2016.

Seven Star LLC can quote Flender couplings from Muscat with the manufacturer brochure available before quotation.

How the ATEX marking is read

The brochure explains the marking, for example II 2G Ex h IIC T6…T4 Gb X for gases and II 2D Ex h IIIC T85 degC…110 degC Db X for dust, plus I M2 Ex h Mb X for underground mining. Group II category 2 equipment can be used in zones 1 and 2 for gas and zones 21 and 22 for dust. The ignition protection types used are constructional safety (c), control of ignition sources (b) and liquid immersion (k). The X in the marking signals special conditions of use.

The zone classification depends on the probability that a hazardous atmosphere is present: zone 0 or 20 continuously or for long periods, zone 1 or 21 occasionally, and zone 2 or 22 rarely and for a short time. Gas groups are IIA (propane), IIB (ethylene) and IIC (hydrogen), and the temperature classes run from T1 (450 degC maximum surface temperature) to T6 (85 degC). Flender products also carry the CE mark and the Eurasian EAC mark for the customs union of Russia, Belarus and Kazakhstan.

• Flexible: N-EUPEX, N-EUPEX DS, RUPEX, N-BIPEX, ELPEX-S
• Backlash-free all-steel: N-ARPEX, ARPEX ARP, ARS/ARC, ARW, ART
• Gear couplings: ZAPEX ZW and ZN
• Hydrodynamic: FLUDEX

Range overview from the brochure

What to confirm before ordering

The brochure is an overview and does not give dimensions or ordering codes for a specific coupling. Send the coupling family and size, torque and speed, the ATEX category and gas group or dust group required, the temperature class, and shaft diameters. Seven Star LLC will check the request against the manufacturer data.

Where ATEX couplings are used

A shaft coupling joins a driving machine, usually an electric motor, to the driven machine: a pump, compressor, fan, mixer, conveyor or gearbox. When that drive train stands in an area where a flammable gas, vapour or dust atmosphere can occur, every part of it must be suitable for the zone, not only the motor. A coupling can become a source of ignition through hot surfaces or mechanical sparks if it is unsuitable or poorly maintained, which is why Flender certifies its couplings under the ATEX directive and marks them with the category, group and temperature class. Typical locations include oil and gas facilities, refineries, chemical and petrochemical plants, fuel terminals, grain and powder handling, and underground mining for the families carrying the mining marking. In these plants the coupling is chosen as part of the overall explosion protection concept of the machine set.

Choosing a coupling family

The families listed above serve different mechanical needs, and the ATEX certification does not change that basic choice. Torsionally flexible couplings such as N-EUPEX and RUPEX damp shocks and tolerate some misalignment, which makes them a common choice for pumps, fans and general machinery. N-BIPEX adds freedom from backlash for drives where that matters. ELPEX-S is highly flexible and suits drives with nonuniform torque. The all-steel ARPEX families are torsionally rigid and are often chosen for higher-speed machinery where a precise connection is needed. ZAPEX gear couplings handle heavy-duty drives, and the FLUDEX hydrodynamic coupling allows a soft start of the driven machine. Start from the mechanical duty of the drive train, select the family that suits it, and then confirm that the chosen family and size carry the ATEX marking required for the zone.

Installation and operating considerations

The X in the marking means that special conditions of use apply, and these are set out in the Flender operating instructions for each family. They typically cover alignment, the operating limits of the coupling and the inspection intervals, and they must be followed for the marking to remain valid. Alignment of the shafts should be checked carefully during installation and after any work on the machine set, because poor alignment increases wear and heat. Guards around the coupling must be suitable for the zone as well. During commissioning, check that the machine runs smoothly and without unusual noise or vibration, and record the alignment values and inspection results in the equipment file so that later inspections can be compared with them.

How to specify your RFQ

A coupling request should describe the drive train as well as the coupling. Please give the coupling family and size if known, the driving and driven machines, the power or torque and the speed, the shaft diameters and the distance between the shaft ends. For the explosion protection, state the zone, the gas or dust group and the temperature class required. If an existing coupling is being replaced, send its nameplate data and a photo of the installed unit. Add the quantity and delivery point, and we will check the request against the Flender documentation before quoting.

Documents and quotation

To request a quotation for the FLENDER ATEX coupling, send Seven Star LLC the full model or order code, quantity, and any nameplate data from an existing unit that is being replaced or matched. Our Muscat team checks the request against the manufacturer document, which can be downloaded from this page, and replies with a formal quotation. Prices, stock and lead times are confirmed per inquiry.

Related reading on this site: the motors, pumps and turbines category.