There are a number of factors that influence Falk F coupling selection. The first step, of course, is to calculate your torque requirements – grid-style F couplings are designed to handle the most torque of any coupling type. The next rating to consider is service factor.

A coupling’s service factor is based on the estimated severity of torque during operation (culled from engineer experience). In other words, this standard rating system indicates how much torque fluctuation the coupling can withstand while the unit is running. The following is a basic breakdown of service factors for F couplings.

1.0: Couplings with the lowest service factor requires fairly constant torque, such as from centrifugal pumps, blowers or compressors.

1.5: These couplings are built to handle continuous operation with minor torque variations, such as from plastic extruders or forced draft fans.

2.0: This service factor is acceptable for the light shock loads from metal extruders or cooling towers.

2.5: These couplings can endure moderate shock loads from applications such as stone crushers and vibrating screens.

3.0: Systems with heavy shock loads and some negative torques – including roughing mills, reciprocating pumps and compressors – will require this rugged service factor.

For applications involving frequent torque reversals that don’t necessarily cause reverse rotations, consult a Falk engineering expert such as those at Mar-Dustrial. Our experienced, highly trained staff can help you select the right F coupling for the job.

A failed coupling can spell disaster for an industrial operation. At minimum, you’re looking at downtime while the repair is made; at its worst, a broken coupling can cause massive financial loss in the form of damaged equipment. Although Falk F couplings have a reputation for longevity and durability – they transmit torque without slip and can accommodate shaft misalignment – they’re not infallible. However, by being aware of the common types of F coupling failures, you can catch problems before they become calamities.

Grid Failures

The grid within an F coupling is a length of flexible alloy steel that snakes through the coupling and connects the two hubs. Its role is to absorb changes in the load, allowing the coupling to continue transmitting torque despite these variations. When cyclic load changes exceed the coupling’s ability to absorb them (often due to torque overload or misalignment), the grid can snap.

How to avoid: Remove the overload from the system, or choose a coupling size capable of handling it.

Hub Failures

An F coupling’s hub teeth are engineered to have at least double the fatigue strength of the grid, which means these types of failures are much less common. Yet a shock or high peak load can still cause the teeth to break or become permanently deformed. A tooth fracture of this type typically occurs after a grid failure, which means the same measures taken to protect the grid will also prevent tooth damage.

The hub shank is another area of vulnerability to consider. Occasionally, cracks may form in the shank, extending through set screw hole or at a keyway corner. Such failures are usually caused by poor installation techniques, which can result in impact loads on the hub.

How to avoid: Ensure the coupling is installed properly, and keep up on regular maintenance.

With correct installation and regular maintenance, F couplings can keep your machinery humming along. If you do experience a coupling failure, it’s critical to take the necessary steps to diagnose the cause and remedy the problem. Here at Mar-Dustrial, we conduct a failure analysis as part of our Falk Repair & Renew services to help you prevent the issue from becoming a recurring one.