How to Check Pump Coupling Alignment

Poor pump performance often happens due to a factor outside the pump itself: alignment. Specifically, the alignment of the coupling that connects the motor to the pump. Misalignments are the root cause of over 50% of failures in rotating equipment, and a single misaligned pump can cost thousands of dollars in repairs, maintenance, and utility bills annually.

The pump coupling connects the drive shaft from the motor and the driven shaft of the pump. When the coupling is aligned properly, the pump operates smoothly and efficiently receives power from the motor.

But if the coupling is misaligned, it can lead to excessive vibration, premature wear on bearings and seals, energy loss, and reduced equipment lifespan. All of these lead to increased maintenance costs, unexpected downtime, and a higher risk of failure during critical operations.

When done correctly, pump coupling alignment helps keep equipment running reliably and avoids problems that can lead to unexpected failures. Here, we’ll discuss how to locate misalignment in pump couplings and the methods you can use to correct it.

Table of Contents

·       Symptoms of Pump Coupling Misalignment

·       How to Check Pump Coupling Alignment

·       Common Problems Leading to Pump Misalignment

·       How to Simplify Pump Coupling Alignment with Laser Alignment Tools and Services

Symptoms of Pump Coupling Misalignment

Knowing the signs of pump coupling misalignment is the first step to fixing it. These are the most common:

• Excessive heat generation
• Excessive vibration and noise
• Loose bolts where the pump is attached to the foundation
• Wear or failures in components like seals or bearings
• Coupling damage

Misaligned pumps most often give themselves away through sound and vibration. You might hear a low rumble, grinding, or rattling noise that changes with speed or load. In severe cases, the coupling may “clank” or “chirp” as it rotates, especially if there’s excessive backlash. Misalignment often causes noticeable vibration that you can feel by lightly placing a hand on the pump or motor housing. That vibration may intensify over time or fluctuate with temperature as thermal growth sets in.

These symptoms signal potential alignment issues and indicate high levels of equipment stress that wear the machine out faster than it should. Even if you don’t suspect misalignment at a certain pump coupling, regular alignment checks can help you spot issues that might affect performance.

How to Check Pump Coupling Alignment

While a small amount of misalignment may seem harmless, even a few thousandths of an inch outside tolerance can lead to excessive vibration, heat, and accelerated wear. Alignment tolerances define the acceptable range of misalignment between coupled shafts. These tolerances vary based on shaft speed, coupling type, and manufacturer specifications. Outside of tolerance, machinery performance and reliability start to degrade.

There are four main ways that technicians typically check alignment:

Visual/Straightedge Method

This is the most rudimentary method of checking pump alignment and doesn’t require any specialized tools – just your eyes and a straightedge. However, visual coupling inspections will only catch serious misalignments. Even if your pump coupling doesn’t show any obvious signs of misalignment, it’s still important to use a more precise method to confirm the coupling is properly aligned.

Here’s how to perform a simple inspection with a straightedge:

1. Power down the equipment
2. Inspect the coupling by removing the cover. If there is visible space between the coupling faces, or if the shafts appear to be at different heights, that’s an indication that there may be misalignment.
3. Place a straightedge across the coupling hubs to check for gaps between the straight edge and the coupling surface. If the gap is uneven across the face, it may indicate angular misalignment. If the straightedge rocks or doesn’t lie flat along the shaft, it could be parallel (offset) misalignment.
4. Check for coupling wear, such as uneven wear patterns, cracked inserts, or rubber fatigue in flexible couplings. You can use these visual observations as a starting point for a more accurate diagnosis with specialized tools.

Feeler Gauge Method

Feeler gauges are thin metal blades of known thickness used to measure gaps between components. In coupling alignment, they help check for angular misalignment between the faces of the coupling hubs. However, they can only measure angular misalignment and cannot identify parallel misalignment.

To use a feeler gauge to test alignment, follow these steps:

1. Power down the equipment
2. With the shafts in a stationary position, insert the feeler gauge between the coupling faces at several points around the circumference.
3. Compare the readings. If the thickness of the gap changes around the coupling, you likely have angular misalignment because the faces of the coupling hubs aren’t perfectly parallel.

Dial Indicators

Dial indicators are mechanical gauges that measure small distances with high precision. They’re a more accurate method than feeler gauges or straightedges and can detect both angular and offset misalignment. Still, they require training and careful setup, and are often time-consuming. Surface imperfections and mounting errors can also impact measurement results.

To get an alignment reading with a dial indicator:

1. Power down the equipment
2. Mount dial indicators on the shaft or coupling hub. You will typically use two indicators: one to measure face runout (angular misalignment) and one to measure rim runout (offset misalignment).
3. Record and interpret the readings. Uneven face readings indicate angular misalignment, while uneven rim readings indicate offset misalignment.

Laser Alignment Systems

The most user-friendly and precise way to check for pump coupling alignment is with a laser alignment system. Laser alignment systems use a laser beam and precision sensors to detect misalignment in horizontal and vertical planes, and can detect both angular and offset misalignment. They have high accuracy, quick setup, and most systems include reporting and data-capturing features.

To measure with a laser alignment system:

1. Power down the equipment
2. Mount the laser and sensor units onto each shaft or coupling hub using brackets. These tools are designed to self-calibrate and compensate for shaft rotation.
3. Slowly rotate the shafts, either manually or using the motor, to allow the system to take readings at different points.
4. The display unit or tablet shows real-time misalignment data, both angular and offset, and gives a graphic representation of shaft positions.

No matter which method you use, identifying the shaft misalignment is only the first step to fixing the problem. Next, you’ll need to make adjustments to the location of the pump, motor, or both and re-measure until you’ve reached the proper alignment. Laser alignment tools make it easy to make multiple checks, rather than manually measuring with hand tools like straightedges and feeler gauges, which are less accurate.

Common Problems Leading to Pump Misalignment

Even when pump coupling alignment appears correct, other alignment-related issues can compromise system performance and lead to premature failure. These faults can mimic or mask misalignment, making accurate diagnosis and correction more difficult without the right tools.

Soft Foot

Soft foot occurs when one or more of the motor feet do not sit flat on the baseplate. This causes the motor frame to distort when the bolts are tightened, leading to shaft misalignment. If soft foot isn’t corrected before alignment, it can throw off your readings and undo any adjustments you make.

Runout

Runout refers to the deviation of a shaft or coupling hub from true rotation. It can result from bent shafts, worn bearings, or eccentric couplings. Excessive runout can make it nearly impossible to achieve proper coupling alignment and often leads to excessive pump vibration and wear.

Thermal Growth

When machinery heats up during operation, metal components expand. If teams don’t account for thermal expansionduring the alignment process, the shafts may move out of alignment as the system reaches operating temperature.

Backlash

Backlash is the small amount of play or looseness in flexible couplings. While some movement is normal, excessive backlash can affect alignment readings, especially when using dial indicators or manual methods.

Simplify Pump Coupling Alignment with Laser Alignment Tools and Services

While pump coupling alignment is a common maintenance task, it can be complex and time-consuming when using traditional tools.

Fortunately, laser shaft alignment tools offer a faster, more accurate, and more repeatable solution, even when aligning complex installations. They’re highly accurate and guide your team step-by-step through the coupling alignment procedure. Built-in software automates many of the calculations that are typically prone to human error.

Laser alignment tools automatically compensate for backlash and are capable of detecting conditions like soft foot, giving you the information you need to achieve precision alignment. They also allow you to account for thermal growth by calculating expansion offsets in advance, so you can align components cold, knowing they’ll stay within alignment tolerance at operating temperature.

With Prüftechnik laser alignment systems, you can perform precise alignments in-house or rely on our expert alignment services to get your machinery back on track quickly and confidently. Explore our full suite of laser shaft alignment tools here.