Pre-alignment is a crucial preparatory step that ensures accurate alignment and effective machine operation and various checks such as pipe strain and bearing clearances.
Pre-alignment insights
- Pre-alignment is an important part of machine maintenance and is a crucial process for accurate machine alignment.
- Proper pre-alignment fosters machine efficiency and lists specific steps and tools for effective execution.
Correct alignment is a keystone of a successful predictive maintenance routine. However, it is crucial not to overlook the importance of pre-alignment procedures. Dedicating time to these steps ensures the alignments are not only accurate but will also remain effective for a substantial period. At the 2023 EASA Convention, Acoem — a company that specializes in machine maintenance solutions — discussed the importance and steps of pre-alignment in a booklet.
Pre-alignment involves tasks that need to be completed before attempting alignment. It serves as the foundational groundwork that directly impacts the accuracy of the subsequent alignment process. To carry out these steps, the following tools area required:
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Straightedge
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Wrenches
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Shims
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Feeler.
Step 1: Rough alignments
A rough alignment begins with measurements on both vertical and horizontal planes. To execute this, position a straightedge on the machine’s highest hub. A shim is slid under the straightedge bottom, brushing the lower part of the hub. The four bolts should be loosened and an appropriately-sized shim slipped under all four feet. Placing the straightedge on the hub again allows the user to verify the horizontal and vertical planes. The straightedge should align perfectly with the hub surface, signifying no offset. Users also should remember to keep the hold-down bolts loose for the next step.
Step 2: Eliminating obvious soft foot
Obvious soft foot is a condition where all four feet of the machine do not sit on a common plane. If uncorrected, the movable machine will rest in a different position every time the bolts are tightened or loosened, making accurate measurement and correction of misalignment challenging. This helps ensure each foot is bearing an equal amount of weight.
Step 3: Bolt tightening
Having achieved rough alignment and corrected the obvious soft foot, it’s time to tighten the bolts. This is not a haphazard procedure; it follows a specific pattern as shown below.
Step 4: Final soft foot correction
With the bolts securely tightened, it’s now time to inspect for soft foot, one foot at a time. Loosening one hold-down bolt at a time allows a more precise measurement and correction of any residual soft foot. It’s also advisable to check multiple places around the foot to account for any angled soft foot.
Additional pre-alignment steps
Before diving into alignment, we recommend several additional pre-alignment steps:
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Cleaning the machine feet and base
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Consolidating shim packs
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Checking for runout
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Checking for pipe strain
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Checking bearing clearances
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Checking for hub separation on the spacer coupling.
These steps are pivotal regardless of whether a dial indicator system or a laser alignment system is being used. The pre-alignment process is an investment in machinery’s longevity and performance. These steps may appear time-consuming, but they are essential to ensuring accurate alignment and efficient and reliable machine operation.
