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Brand: Flender
Flender RUPEX Pin and Bush Coupling
Description
A pin and bush coupling for harsh duty, sizes 105 to 2000
The Flender RUPEX coupling is a universally applicable, torsionally flexible, damping pin and bush coupling. Flender’s assembly and operating instructions M3600-01 (version 03/2026) cover the types RWN and RWS, which have two shaft-hub connections, and RFN and RFS, which have one shaft-hub connection and a flange. The coupling is designed to withstand high torques and harsh operating conditions, and the family catalog gives its rated torque range as 120 Nm to 1,690,000 Nm.
RWN and RWS can be fitted with an axial backlash limitation in sizes 228 to 1600, which suits drives where the motor has no separate thrust bearing. The RWN and RWS types are also offered as an AIQ Detect-ready version with a magnet on the outer diameter for wear monitoring; the AIQ Detect system itself must be ordered separately.
Technical specifications
| Parameter | Specification |
|---|---|
| Types | RWN, RWS (two shaft-hub connections); RFN, RFS (flange type) |
| Sizes | 105 to 2,000 (instructions list sizes 105 to 2000) |
| Document | M3600-01en, version 03/2026 |
| RWN size 105 | n max 7,000 rpm; max bore 35 / 42 mm; DA 105 mm; 1.9 kg |
| RWN size 228 | n max 3,300 rpm; max bore 90 / 95 mm; DA 228 mm; 18 kg |
| RWN size 400 | n max 2,050 rpm; max bore 150 mm; DA 400 mm; 99 kg |
| RWN size 630 | n max 1,280 rpm; max bore 140 to 220 mm; DA 630 mm; 345 to 389 kg |
| Bolt tightening torque | 8 Nm (size 105) to 2,000 Nm (sizes 1800 and 2000), bolts of strength class 8.8 |
| Max torsional backlash | 3.0 mm (size 105) to 20.0 mm (size 2000) |
| Maintenance | Initial check 3 months after commissioning, then every 12 months |
| Buffer materials | NBR 80 Shore A standard (-50 to +80 C); NBR 65 soft; NBR 90 hard; NBR 80 electrically insulating, green (-30 to +80 C) |
| Misalignment | Permitted values depend on speed and size; reduce by 20 percent with axial backlash limitation |
| ATEX marking | II 2G Ex h IIC T6…T4 Gb X; II 2D Ex h IIIC T85 C…110 C Db X; I M2 Ex h Mb X (not for axial backlash limitation versions) |
Maintenance and wear
Wear is concentrated in the buffers. The instructions require the torsional backlash to be checked at the stated intervals against the maximum permitted value for the size, and complete sets of buffers of the same type and age must be replaced together. Buffers can be stored for up to five years away from sunlight and aggressive media. The permitted radial and angular misalignment falls as speed rises, following DeltaK = (0.1 + DA / 1,000) x 40 / sqrt(n).
Ordering notes
State coupling type, size, bore and keyway, speed, torque, buffer hardness, whether axial backlash limitation or wear monitoring is needed and whether the unit is for an explosive atmosphere, since couplings with axial backlash limitation are not approved for it. For gearbox pairings see the published Flender ONE gear unit; coupling items are grouped in Electric Motors.
Documents and quotation
The Flender document is attached. Seven Star LLC supplies Flender couplings on request and quotes against the exact type, size and bore. The attached document is the manufacturer’s assembly and operating manual, not a sales brochure; it contains the dimension and speed tables and safety instructions.
Datasheets & Documents
- Datasheet Flender RUPEX assembly and operating instructions M3600-01en (03/2026) Download
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About brand
Large industrial gearboxes are the product most engineers associate with Flender, a company founded in 1899 and based in Bocholt, Germany, that builds gear units, couplings and drive systems. Seven Star LLC sources and supplies Flender gear units and their spare parts for mills, conveyors, pumps and marine drives in Oman, working from the nameplate data. On some nameplates the name appears as Siemens Flender.
Flender gearbox types listed here
Four items are listed. Flender ONE is the manufacturer's redesigned single-stage helical gear unit. The H2SV 09 is a two-stage helical gear unit of size 09 with a solid output shaft, shown here with a cooling coil and oil tank. The NAVILUS line covers marine gearboxes, listed in a multiple-input, single-output arrangement that brings several engines onto one propeller shaft, and in a version for dredgers. Flender couplings such as the flexible N-EUPEX type are often ordered with a gear unit.
Ordering a Flender gearbox or parts: what we need
Send a photo of the nameplate showing type, size, serial or order number, ratio, power and speeds. For spares, the serial number lets the parts list be traced, so add the item number of the bearing, seal or gear set you need. For a new unit, give the driven machine, motor power and speed, output speed, mounting position, shaft arrangement, ambient temperature and cooling method. Marine and dredger gearboxes for GCC yards also need the class society.
Browse Flender products by category: Electromotors, Electric Motors & Pumps.
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Frequently Asked Questions
Which RUPEX types does the manual cover?
RWN, RWS, RFN and RFS.
Is axial backlash limitation available?
Yes, on RWN and RWS in sizes 228 to 1600; such couplings are not approved for explosive atmospheres.
How often must torsional backlash be checked?
Three months after commissioning, then every 12 months.
What buffer materials are used?
NBR in 80 Shore A standard, 65 soft, 90 hard and an electrically insulating 80 Shore A version.
What is AIQ Detect-ready?
A version with a magnet on the outer diameter for wear monitoring; the AIQ Detect system is ordered separately.
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