3 Causes of Coupling Failure In Pumps

Shaft couplings are one of the most inexpensive parts on a pump, yet one of the most critical. Although coupling selection is frequently an afterthought, coupling failure can mean a reliability disaster.

Watch out for coupling failure when a pump demonstrates these warning signs:

• Excessive noise and/or vibration
• Premature mechanical seal and bearing failure
• Increased power consumption

What's causing these warning signs to present themselves? At Crane Engineering, we find the root cause of coupling failure ladders up to one of the following reasons.

1. Shaft Misalignment

Up to 50% of damage to rotating equipment is directly related to misalignment. Misalignment can be caused by improper installation of the pump and motor, pipe strain, even bent shafts.

Even if a pump has been properly laser aligned at installation, it can still become misaligned during operation due to dynamic load shifts and thermal growth. More about that in a previous post: "How Do Laser Aligned Pumps Become Misaligned During Operation?".

For longest coupling life, ensure the pump is laser aligned and adjusted to keep it aligned during operation.

2. Lack of Proper Lubrication

Some couplings, like solid, magnetic, flexible rubber or plastic couplings, do not require lubrication. But couplings such as gear and grid couplings do.

These couplings require lubricant levels are checked 1-2 times per year, and periodically flushed to remove any contaminants that may cause premature failure.

3. Incorrect Coupling Selection

Couplings are largely viewed as commodity items. Oftentimes price and delivery are the only factors in their selection.

Crane Engineering recommends that couplings are selected the appropriate service factor, therefore planning for the worst case scenario. For instance, when couplings are selected, they are generally chosen to be the best fit at normal operating conditions. But what about peak torque conditions, such as start-ups, shutdowns, and upsets? What if the coupling will experience frequent start-ups, shutdowns and upsets? Planning for issues like this, plus misalignment, vibration, heat transfer, and maintenance will decrease downtime (and headaches!) for maintenance staff.

Take Advantage of Technology

Couplings are one of the easiest parts of a pump/motor assembly to overlook. They're also one of the most critical. For the most reliable couplings, always look for ways to minimize the demands placed on them by reducing hard starts and shock loading. Utilize the technology and tools available to ensure this small inexpensive part doesn't become a big expensive problem.

Want to increase your pump reliability? Ask us about your options. We gladly provide technical assistance to businesses and municipalities in Wisconsin and upper Michigan.