5 Reasons Why Couplings
A coupling connects two rotating shafts, allowing rotary motion
and torque. Although couplings are relatively inexpensive and
easy to maintain, their failure can cause major inconveniences
and huge financial losses. There's even a risk of injury. At
Vissers, we believe prevention is better than cure, so look
out for these warning signs that your couplings are about to
" Undue noise or excessive vibrations and wobbling
" Seal or bearing failure, lubricant leakage or contamination
" Higher than normal power consumption
To prevent these warning signs of coupling failure in the first
place, it's important to know the top five reasons why couplings
Misalignment can be caused by improper installation of the pump
and motor, bent shafts or pipe strain. It's important to know
the misalignment conditions of the application when selecting
the coupling - angular, parallel, axial or complex misalignment.
Flexible couplings work best in these conditions. However even
flexible couplings have their limitations, and underestimating
the degree of misalignment can cause loads that surpass coupling
specifications. This can cause excessive wear and premature
failure of bearings. It's also important to take dynamic load
shifts and thermal growth into account. Laser alignment can
help extend coupling life, while regular adjustments may be
required to keep it aligned during operation.
2. Lack of Lubrication
Many couplings, like gear and grid couplings, require proper
lubrication. Check the lubricant levels of these couplings twice
a year and periodically flush to remove contaminants that may
cause premature coupling failure.
3. Incorrect Selection
Price and delivery are often the primary selection factors for
couplings, however selecting incorrect couplings can have dire
consequences for coupling operation. Make sure you select your
couplings in the early stages of the design process to ensure
that the coupling chosen is the right one for the functions
required. For example, fuse couplings don't allow further energy
transfer upon failure, while fail-safe couplings are designed
to continue working even after failure.
When choosing couplings for an application, you must consider
many factors such as misalignment, torque, windup, backlash,
inertia, stiffness, shaft mounting, environmental factors, limitations
on space, service and maintenance factors, and cost. This process
of evaluation must be repeated any time conditions change throughout
the application's lifecycle. Other conditions to be aware of
include dampening - it's important to select a coupling with
the correct amount of dampening (which minimizes shock and vibration
to reduce stress on system components), application shaft speed
(any degree of misalignment can affect safe operation speed
of the couplings) and electrical isolation, as voltage differentials
between shaft ends can lead to bearing and system wear.
4. Improper consideration of inertia, windup or backlash
Couplings need to be suited for their application. Inertia refers
to a coupling's resistance to changes in velocity and this determines
whether the coupling can keep a constant speed in response to
external forces (such as torque). Too much coupling inertia
can degrade the performance of the entire system.
Present in all couplings, windup is known as torsional rigidity
and is the rotational deflection between the driver and the
load, much like winding up a spring. Windup needs to be considered
to maintain accuracy of location, as it may lead to a difference
in angular displacement from one end of the coupling to another.
Backlash is the momentary loss of motion in a coupling, which
is experienced when the direction of torsion is changed - causing
the coupling to bend and compress. Any amount of backlash can
be detrimental to an application, causing lack of accuracy in
positioning and making it difficult to tune the system.
5. Lack of regular maintenance:
Lack of regular maintenance can cause couplings to fail prematurely.
Scheduled inspections should include regular visual inspection
for signs of wear or fatigue, regular cleaning and lubrication
and documented, dated maintenance checks.
If you want to make sure you're choosing the right couplings
for your application, please call our toll-free number 1-800-
367-4180. We have experts on hand to help you choose, install,
and maintain a variety of equipment.