Disc Couplings
"Disc Couplings" are one of the many Flexible Style of shaft couplings available on the industrial/commercial market. As for this information... a significant portion was taken from Lovejoy's website, "Coupling Answers.com". Check it out when you get a chance.
"Disc Couplings" are a popular coupling design that continues to pick up steam within the power transmission industry in large part because they can transmit a significant
amount of torque, while also being minimal maintenance. Unlike lubricated gear and grid couplings, "Disc Pack Couplings" require no lubrication and periodic re-lubrication. This
makes them ideal for applications that are hard to reach or get to... which, given increased maintenance department budget constraints... is broadly appealing across countless
high torque applications and industries.
Disc packs can be visually inspected without taking apart the coupling (a major time savings not true with gear or grid couplings) and have "theoretical infinite life" in
that they have no wearing metal-on-metal misalignment handling flex points (as is the case with lubricated gear and grid couplings). Rather, misalignment handling occurs through
the flexing of unitized disc packs connecting two flanges together. Should a disc pack wear out (generally due to fatigue brought on by excessive misalignment), bolts and the
unitized disc pack can be generally removed and replaced without having to move the installed coupling hubs.
Furthermore (yes, there are a lot of positives with this coupling type), generally being all metal (with no seals or gaskets) gives "Disc Couplings" the ability to withstand
harsh environments. And, lastly, to give one more potential major benefit (based on the application) over their lubricated brethren, "Disc Couplings" have torsional rigidity with
no backlash.
Limitations of "Disc Couplings" include no vibration dampening capability (a strength of elastomeric & grid couplings), and limited misalignment handling capability... particularly in regards to parallel misalignment. (For a disc coupling to handle parallel misalignment, two disc packs must be used.) Additional considerations include speed limitations if not balanced (though these can be overcome as evidence by widespread "Disc Couplings" usage in API 610 and API 671 applications), and possible anti-flail concerns (though, again, anti-flail safety features can be added to many designs).
"Disc Couplings" and their disc packs are generally referred to by the number of bolts they have. Common bolt configurations include 4 bolt, 6 bolt, & 8 bolt. The reason bolt
configurations are even is that torque is only carried in tension across every other leg of a disc pack (while the remaining legs will be in compression). In a 4 bolt design, 2
legs will be carrying the torque. In a 6 bolt, 3 legs... and, in an 8 bolt, 4 legs.
The trade-off between the number of bolts is torque versus misalignment handling capability. More bolts (and more legs sharing the load) can carry higher torque loads, but this
increase also decreases the flexibility of the disc pack and ability of the pack to handle increased misalignment
Disc packs are generally made of thin layers of stainless steel (though materials can vary) that have been "unitized" into a single easy to handle/install/replace unit by use of bushings. Some early and current designs styles still make use of non-unitized layers, which can be a bit trickier to deal with from a maintenance and handling perspective.
While "Disc Couplings" commonly use interference fit hub-to-shaft connections, another hub-to-shaft connection feature available for "Disc Couplings" are Shaft Locking Devices. The advantage of using shaft locking devices is that users can avoid interference fits that require significant maintenance time to remove. The disadvantage of shaft locking devices is the initial upfront cost. Additionally, watching tolerances and understanding the ratings of a shaft locking device are also critical as the shaft locking device may have ratings below the coupling and or system requirements.
So a lot of thought must be evaluated for proper application of a "Disc Coupling". But A.R.&E. can assist you in that process and supply it for you when you're ready to purchase. Give us a call...
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