Every day, applications all over the world ⎼ like pumps, motors, compressors, gearboxes, blowers, mixers and conveyors ⎼ rely on shaft couplings to operate smoothly and efficiently.
But what is it that makes shaft couplings a good fit for a given application?
According to Tim Zerger, IBT’s Power Transmission Business Group Director, couplings are specified based on their ability to handle the application temperatures, torque, speed, horsepower, shaft size, spatial limitations, as well as their ability to accommodate for any misalignment. “As long as the coupling meets these requirements, it can be interchanged with any style,” he says.
So why is it, then, that people rarely deviate from one type? When it comes to the variety of coupling styles available in the marketplace today, there is rarely one “obvious” or “right” answer in determining which coupling is best for your application. In Zerger’s experience, the choice is oftentimes made based on feelings of familiarity or brand loyalty.
If you’ve never evaluated your current coupling selection, we’ve outlined popular coupling styles – and their prominent features – to help you objectively compare the styles, weigh the benefits and ensure you’re maximizing your application life.
Shaft Coupling Guide
Shaft Couplings are transmission components used to connect rotating shafts and absorb misalignments between them. Mechanical couplings can be rigid or flexible, depending on the alignment accuracies of the system and torque requirements.
Sleeve couplings provide a simple way to rigidly connect two shafts of identical diameters. They consist of a solid or split sleeve, a rubber element and two metal hubs. In light to moderate load applications, sleeve couplings may employ set screws and key seat, depending upon the amount of torque to be transmitted. Additionally, sleeve couplings are maintenance-free, absorb torsional shock, allow for end float and accommodate well for parallel and angular misalignment.
While straight and curved jaw couplings can handle high rates of horsepower, they are typically found in smaller, lighter-duty applications. The replaceable spider insert, separated by two hubs, offers a fail-safe design that allows the coupling to still perform if the elastomer fails.
Another advantage of the jaw and spider style coupling is that there is no metal-to-metal contact, eliminating the need for maintenance and increasing resistance to oil, dirt, sand, moisture and grease. Lastly, while this style of coupling is easy to install and align, repair is often a time-consuming task.
Gear couplings are compact and consist of two hubs with external teeth that engage with internal teeth of a flange or sleeve. Additionally, they have a bore capacity for shafts up to 52”. They are often paired with spacer shafts to span the distance between driving and driven equipment and are capable of transmitting proportionately high torques at any speed and at extreme temperatures. However, they also require diligent lubrication to reduce friction and maximize coupling life.
Grid couplings employ spring-like connecting elements that weave between slots in the coupling hubs. The high-strength, tempered steel spring is designed to isolate vibration and cushion shock loads. Unlike other styles, though, grid couplings are not as forgiving with misalignment and require laser alignment upon installation. They have a capacity for both speed up to 6,000 rpm and high torque transmission.
Chain and sprocket couplings are composed of two sprockets, two shafts, a chain and a connecting link or pin. They are capable of transmitting proportionally high torques at low speed, but are inherently noisier than other coupling styles. Chain couplings, because of their simple design, are: easy to align, long-lasting and inexpensive to replace—resulting in an overall low operating cost. However, they require lubrication and have both limited torsional flexibility and low shock dampening capabilities.
Disc couplings are made up of thin steel discs – in a single or double series – bolted to shaft hubs. The flexibility of the discs accommodates especially well for angular misalignment, while providing a torsionally rigid coupling. These couplings are maintenance-free, easily visually inspected and are ideal for precision applications due to their zero backlash design.
Rubber Tire Couplings
This style of coupling is essentially a flexible rubber tire with a bonded in-tension member to carry the load. The “tire” component comes in either EPDM, neoprene rubber or hytrel (urethane), which fits into special hubs and is tightened to the shafts. Rubber tire couplings accommodate up to 3/16 of an inch for parallel misalignment and up to 4 degrees in angular misalignment. Additionally, they are maintenance-free and can come fully split for easy disassembly, quick replacement and less downtime.
DODGE RAPTOR COUPLING
According to Baldor•Dodge®, coupling maintenance and reliability should not monopolize your maintenance team.
That’s why they created the Raptor Coupling, a new take on the standard tire coupling. The Raptor’s easy to assemble, patented split natural rubber element significantly decreases total costs of ownership and extends driven equipment life. Built for drop-in interchangeability, its innovative design also offers easier installation, reduced maintenance and improved reliability in a wide range of new and existing applications. Learn more about the Raptor and get a 5-year Limited Warranty when you upgrade.
Have Additional Questions About Shaft Couplings?
Mechanical Power Transmission has been a cornerstone of the IBT Industrial Solutions business since the company was founded in 1949. If you’re looking for the knowledge and expertise you need to select the best shaft couplings for your application, contact Tim Zerger, the Bearing and Power Transmission Director at IBT Industrial Solutions, or give us a call at 913-677-3151 to learn more.