Flender N-ZAPEX XW and XN Torsionally Rigid Gear Coupling

N-ZAPEX XW and XN gear couplings for rolling mill, cement and heavy drives

The Flender N-ZAPEX is a torsionally rigid gear coupling. It links machine shafts and compensates shaft misalignment with weak restoring forces, combining high transmissible torque with compactness and light weight. Flender’s catalog FLE 10.1 (edition 2026.1, torsionally rigid couplings) presents the XW series (types XWN to XWNV) and the XN series, and names harsh conditions such as drives in the iron smelting and cement industries as typical applications.

Two externally toothed hubs engage in flanged sleeves with internal teeth, connected by two flanges with close-fitting bolts. The crowned teeth permit angular displacement per tooth plane, and radial displacement is absorbed over the distance VA between the tooth planes. Types are built on a modular principle, so application-specific solutions can be delivered quickly.

Technical specifications

XW or XN

The XW series covers the larger sizes, up to the 1676, and offers brake drum, brake disk, coupling sleeve and vertical variants. The XN series is the grease-lubricated, steel design for the smaller and medium sizes with O-ring sealing and the standard, axial-limited, spacer and brake-disk types. The same catalog also contains the N-ARPEX and ARPEX all-steel couplings and the SKZF flange coupling, so a project that must compare gear and disk couplings can use one document; the N-ARPEX has its own page on this site.

Ordering notes

State torque and speed, service factor, shaft diameters and keyways, spacer length, brake element, mounting position and ATEX needs. Permitted misalignment falls at higher speed and torque according to correction factors in the operating instructions. Coupling items are grouped in Electric Motors; a related published product is the Flender ONE gear unit.

How the Flender N-ZAPEX works

A gear coupling carries torque between two shafts through toothed parts, and it allows some angular and radial misalignment. In the N-ZAPEX, two externally toothed hubs engage in flanged sleeves with internal teeth, and two flanges join the sleeves with close-fitting bolts. The crowned teeth permit an angular displacement in each tooth plane, and radial displacement is absorbed over the distance VA between the two tooth planes. The result is a torsionally rigid coupling with high torque in a compact and light design, with weak restoring forces on the shafts.

Where the N-ZAPEX is used

• Rolling mill drives.
• Iron smelting plants.
• Cement industry drives.
• Heavy conveyors and crushers.
• Brake drum and brake disk applications on large drives.

Selection checklist for the N-ZAPEX

• Series: XW for the large sizes, or XN for small and medium sizes.
• Size and rated torque, such as 191 with 17,500 Nm or 390 with 138,000 Nm.
• Maximum torque of twice the rated torque for the XW.
• Type: standard, axial-limited, spacer, brake drum, brake disk or vertical.
• Angular misalignment of 1.3 degrees on XW types and 0.8 degrees on XN types.
• Lubrication with oil or grease on the XW, and grease on the XN.
• Sealing with HO rings or O-rings.
• Shaft diameters and the distance between shaft ends.
• Explosion protection marking when needed.
• Operating speed and the service factor of the drive.

Installation, commissioning and maintenance notes

Align the shafts carefully, within the limits of the catalogue, and tighten the close-fitting bolts to the specified torque. Fill the coupling with the right lubricant as instructed, and check the seals. Inspect the coupling at the intervals of the plant maintenance plan, and look for wear of the teeth, leaks and loose bolts. Keep the catalogue data for the size and type with the machine records.

Requesting a quotation for the Flender N-ZAPEX

Send the rated power, the speed, the shaft diameters and the type. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

Modular design

The couplings are built on a modular principle, so application-specific versions can be delivered quickly.

Explosion protection

The catalogue gives ATEX markings for gas, dust and mining groups, and these should be checked for the selected type.

Coupling family range

The N-ZAPEX series spans from 1,400 Nm to 10,000,000 Nm in the catalogue.

Coupling records

Record the size, the type and the lubricant of each coupling.

Choosing the N-ZAPEX size and type

Start from the drive power, the speed and the shock load, then pick the size whose rated torque covers the duty with the service factor. Check the shaft ends and the distance between them, because spacer, brake drum and brake disk types change the arrangement. The vertical XWNV type is for shafts in the vertical position. For the smaller sizes, the XN series with grease filling and O-ring sealing is the simpler option.

Torque ratings

Examples from the catalogue: size 282 has a rated torque of 57,000 Nm, size 632 has 540,000 Nm, and size 1676 has 10,000,000 Nm.

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 PDF is an excerpt of the manufacturer’s catalog FLE 10.1 (the full file exceeds the hosting limit): front matter, introduction and the N-ZAPEX XW and XN chapters, pages unaltered. This page is separate from the ZAPEX ZW page, which is a different product line with its own manual.