Falk Couplings-Elastomeric
This post provides a bird’s eye view of how to maintain and optimize FALK Couplings. Couplings are key components in industrial systems; a poorly selected or maintained coupling can lead to downtime, system failure, and costly repairs. Read on to learn the basics about couplings, including their purposes, common problems, maintenance recommendations, and optimization suggestions. For more detailed information on specific coupling situations, call us. Our expert engineers can answer all your coupling questions.
FALK Couplings: How They Work
Couplings connect shafts to allow the transfer of power. Here are a few uses for couplings:
–To transfer power between driving and driven parts.
–To reduce shock loads from one shaft to another.
–To allow some misalignment between shafts.
–To protect the system against overloads (by automatically disconnecting when a torque limit is exceeded, for instance).
–To allow for disconnection if repairs are required.
There are many different types of couplings. For instance, gear couplings (AKA G couplings) use gear teeth to transmit power between shafts, while grid couplings (AKA T or F couplings) use a steel grid to transfer power. Within each of these categories are several additional designs. There are dozens of types of couplings to accommodate a world of potential shaft arrangements, torque loads, and operation requirements.
Common Problems with Couplings
–Can’t find replacement. Many industrial systems use F couplings, a series of popular Falk couplings featuring a flexible steel grid that reduces peak shock loads by up to 30%, while allowing for some shaft misalignment. Falk no longer manufactures F couplings, as their new T couplings are superior. (Unlike F couplings, T couplings may be replaced in-place, with minimal disassembly required.) For managers and engineers that hope to replace an F coupling, there’s one option left: contact our staff. We maintain a wide inventory of surplus FALK parts, including F couplings.
—Soft Foot. Soft foot occurs when one corner of a gearbox sits higher or lower than the others. Basically, you can expect soft foot whenever there’s a lackluster proper connection between the casing and the baseplate. There are several root causes of soft foot:
a) Damaged baseplate, feet, or underlying foundation,
b) Oil or other items between the feet and the base,
c) Incorrectly installed shims beneath the feet,
d) A pipe or some other object prevents the gearbox from sitting on its feet properly
e) Too much tension on the feet, due to jackbolts.
You know you have soft foot if tightening a bolt causes a decrease in vibration amplitude. You can tighten each foot bolt, one at a time, to see if this occurs. Soft foot is a big problem as it causes looseness, clearance issues, and misalignment. For more details on minimizing soft foot, check out our blog on the topic.
–F Coupling Grid Failure. Overload and misalignment can cause excessive cyclic load changes within F couplings. If the force is greater than the grid’s ability to absorb it, the grid can snap.
–Hub Failure. Hub failure on Falk Couplings is designed to be twice that of the grid, so this problem is less common. Still, high peak loads can cause break an F couplings’ teeth. Additionally, the hub shank may be cracked due to improper installation.
A failed coupling should be carefully documented and studied, so as to avoid future failures. Any available stats about the surrounding environment should also be noted, as they may suggest a cause for the failure.
When to Schedule Service Maintenance for Couplings
In general, you want to schedule consistent maintenance to extend the life of your couplings and ensure smooth operation. The maintenance setting for your schema will depend on a number of factors, including environment, operation requirements, job cycles, and end application. A properly researched maintenance schedule will keep the whole system working smoothly, so that no one piece is overloaded.
Maintenance tasks may include:
–Noise monitoring. Sound vibrations are educational when tracked over time. They may change when a part is being jammed, for instance.
–Temperature tracking. By watching temperature at various points in the system, engineers can note unusual spikes and track down problems.
–Checking fluid levels, including lubrication.
Should you have a failure, call us. Our Falk RENEW shop operates on a 24/7 schedule, and we can typically repair parts for a fraction of what a new gearbox would cost.
How to Get the Most Out of your Couplings
1. Choose the right one. There are many different considerations for choosing a coupling, including
service factor. This describes how much torque a coupling can withstand. Setups with constant torques often require the minimal service factor of 1.0, while heavy shock loads with some negative torques require the highest service factor of 3.0. For coupling selection expert advice, including service factor recommendations, contact our on-staff engineers. They may recommend a high torque coupling, such as a Falk lifelign gear G coupling.
Environment, surrounding parts, and service requirements are additional considerations for coupling selection. A coupling must provide a strong shaft connection while operating reliably in a given setting. Additional variables to be considered when choosing a coupling include:
–Space parameters
–Torque, including start/stop needs and peak load limits.
–Budget
–Stiffness of the coupling
–Shaft mounting limitations
–RPM
–Service factors
–Inertia
Fastidious coupling selection should be done early in the design process, to avoid costly adjustments later.
2. Minimize misalignment. Laser alignment tools and alignment computers can help you effectively test for alignment. At the very least you’ll need to use a straight edge, spacer bar, and feelers to check for gaps and angular alignment. This should be done consistently, as misalignment drags down overall efficiency and can lead to gearbox failure over time. Additionally, certain applications, such as motion control, require zero-backlash couplings.
3. Follow Installation Recommendations. Different couplings have different fit requirements. For instance, Falk T couplings come in either clearance fit (generally smaller couplings) or interference fit (typically larger couplings). When installing interference fit T couplings, it’s required that they be heated to 275 degrees Fahrenheit. The same is not true for clearance fit couplings. To extend the life of any coupling, carefully follow Falk’s installation guidelines.
4. Keep Couplings Properly Lubricated. Lubrication is the lifeblood of gearboxes—without it, failure is inevitable. Each coupling will have its own preferred type of lubrication. Many are compatible with grease, a combination of thickener and base oil. Over time, the oil seeps out of the thickener and infiltrates the coupling’s parts to guard against friction. Some couplings, however, require Long Term Grease (LTG). For instance, T couplings often see centrifugal force, which can cause regular grease to separate and cause build-up of thickener between grid grooves. LTG resolves this problem by changing consistency according to operating conditions, thereby resisting separation. A Mar-Dustrial expert can advise you on which lubricant to use with your couplings.
Posted under Products/Services on Tuesday, July 15th, 2014