Coupling Alignment Procedure: Arrow Indicator and Laser Alignment Methods

1. Scope of Application and Purpose

This practical guide is intended for maintenance technicians, engineers and plant managers who are responsible for the installation, commissioning and maintenance of rotary equipment. The goal is to provide detailed step-by-step instructions for accurately aligning the shafts of coupled units using both traditional pointer indicators and modern laser systems. Correct alignment of couplings is critical to ensure reliable operation of equipment, extend the life of bearings, seals and the coupling itself, as well as to reduce energy consumption and vibration levels.

Alignment should be performed in the following cases:

• After installing new equipment.
• During scheduled maintenance.
• After repairing or replacing any components that affect the relative position of the shafts (for example, bearings, housing).
• If increased vibration, abnormal noise or overheating of bearings is detected.

2. Precautions

DANGER: Before starting any coupling alignment work be sure to perform the Lockout/Tagout - LOTO procedure of the power sources in accordance with the company's internal standards and the requirements of the EN ISO 14118. Make sure that all power sources are disconnected and blocked, and the kinetic energy of the moving parts is completely discharged. Failure to do so could result in serious injury or death.

DANGER: Always wear appropriate personal protective equipment (PPE): safety glasses (according to EN 166), protective gloves (according to EN 388), safety shoes (according to EN ISO 20345) ​​and, if necessary, protective clothing. Avoid loose clothing that can be caught in moving parts.

CAUTION: Hot surfaces! Some equipment components may be hot. Allow the equipment to cool to a safe temperature or use heat resistant gloves.

3. Necessary Tools and Materials

4. Pre-release Inspection Checklist

Before beginning the alignment procedure, perform the following inspection to ensure that there are no factors that could distort the results or complicate the process.

5. Step-by-step Procedure

5.1. Preparatory Works

1. CAUTION: Make sure the LOTO procedure is completed and the power sources are completely isolated. Install a guard or sign on the free end of the motor shaft or rotating equipment that prohibits unauthorized manual rotation.

2. Clean all contacting surfaces: shafts, half-coupling ends, equipment support legs, foundation plates. Use a metal brush and metal cleaner, then wipe with lint-free cloths.

3. Perform a soft foot check for each unit.

   1. Tighten all fastening bolts of the legs of the unit with a torque wrench to the values ​​recommended by the manufacturer (for example, for an M16 bolt of strength class 8.8 — 160 Nm).
   2. Install the arrow indicator on the body of the unit near one of the legs so that its probe rests on the base plate or frame.
   3. Release the bolt of this leg. Record the indicator reading.
   4. Tighten the bolt again to the recommended torque. If the indicator reading has changed by more than 0.05 mm, this indicates the presence of a "soft paw".
   5. Eliminate the "soft leg" by adding or removing a thin shim (shim) under the corresponding leg until the offset is less than 0.05 mm.
   6. Repeat for all paws. Neglecting the elimination of the "soft paw" will lead to distortion of the alignment results and increased vibration.

4. Perform a rough alignment using a ruler or tape measure. The goal is to reduce the initial displacement to 0.5-1.0 mm to ensure the correct operation of the measuring devices.

5.2. Arrow Indicator Method (Reverse Arrow Indicator Method)

This method allows you to measure the radial (parallel) and angular displacement of the shafts.

1. Installation of indicators:

   1. Install the magnetic base of the arrow indicator No. 1 on the half coupling of the unit No. 1 (as a rule, stationary, for example, the pump), so that its probe rests on the end surface of the half coupling of the unit No. 2. This will measure the angular displacement (FACE).
   2. Install the magnetic base of the arrow indicator No. 2 on the half coupling of the unit No. 1 so that its probe rests on the radial surface (edge) of the half coupling of the unit No. 2. This will allow the radial displacement (RIM) to be measured.
   3. Ensure a secure fit and no sagging.

2. Measurements:

   1. Select the zero point (usually 12 o'clock - from the top). Set the readings of both indicators to zero.
   2. Rotate both shafts simultaneously through 90°, 180°, 270° and 360° (return to zero). Record the reading for each point. It is important that both shafts rotate together to avoid coupling backlash.
   3. Example of a table for recording readings:

   Position of Valu	Indicator 1 (End)	Indicator 2 (Radial)
   0° (top)	0.00 mm	0.00 mm
   90° (right)	+0.03 mm	-0.02 mm
   180° (bottom)	+0.05 mm	+0.04 mm
   270° (left)	+0.02 mm	-0.03 mm

3. Calculation and Analysis:

   1. Calculate the radial displacement: (Reading 180° - Reading 0°) / 2.
   2. Calculate the angular misalignment: Use the end indicator reading and the measuring diameter (distance from the shaft axis to the dipstick). The calculation formula depends on the specific configuration. Some alignment methods use special formulas or graphical methods.
   3. Compare the values ​​obtained with the recommended tolerances.

   Operating Speed (rpm)	Radial Offset (Offset)	Angularity
   Up to 1000	< 0.05 mm	< 0.05 mm per 100 mm of coupling length
   1000 - 3600	< 0.03 mm	< 0.03 mm per 100 mm of coupling length
   More than 3600	< 0.02 mm	< 0.02 mm per 100 mm of coupling length

4. Correction of Position:

   1. Based on the calculations, determine how much and in which direction the moving unit (usually the engine) needs to be moved.
   2. For vertical movement (up/down), add or remove adjustment plates (shims) under the support legs.
   3. For horizontal movement (left/right) use the mounting bolts and a hydraulic tool or a hammer with a rubber pad for precise movement.
   4. After each correction (especially significant), re-tighten the bolts of the paws with a torque wrench and repeat the measurements until the acceptable values ​​are reached. Common mistake: Moving too much at once, ignoring the effect of tightening bolts on position.

5.3. Laser Leveling Method

Laser systems greatly simplify and speed up the process by providing results in digital format and often including software to calculate the correction.

1. Assembly of Measuring Blocks:

   1. Install the laser emitter and receiver on the coupling halves of the two units according to the system manufacturer's instructions. Make sure it is securely fastened.
   2. Connect the measuring units to the display unit or tablet.

2. Hardware Data Entry:

   1. In the system software, enter the necessary geometric data of the units: distances between the support legs of the moving unit (for example, L1, L2), the distance from the center of the receiver attachment to the nearest support leg, the distance between the centers of the emitter and the receiver (the distance between the half couplings). Error: Entering these dimensions incorrectly will result in incorrect correction recommendations.

3. Measurements:

   1. Follow the prompts of the software. It is usually necessary to turn the shafts to 3 positions (for example, 9, 12 and 3 o'clock) or make a continuous rotation of 180° with the readings fixed at the given points.
   2. The system will automatically calculate and display the current radial (parallel) and angular (axial) displacement.

4. Analysis and Correction:

   1. The software will display the current offset values and, critically, suggest exact values for adding/removing shims under the support legs and the amount of horizontal offset.
   2. Make a vertical correction by adding or removing shims.
   3. Perform a horizontal correction by shifting the unit.
   4. Many modern systems allow correction in "real time" (live move), showing how the position of the shafts changes during shifting or shimming.
   5. Tolerances: Follow the tolerances recommended by the laser system manufacturer or relevant standards, such as ISO 15243 for bearings that indirectly affect alignment requirements. For example, for equipment with a speed of up to 3000 rpm, permissible deviations for radial displacement can be 0.02-0.03 mm, for angular - 0.03-0.04 mm/100 mm.
   6. After each correction, repeat the measurement until all values ​​fall within the tolerances. Error: Ignoring small but constant deviations from tolerances. Always strive for "perfect" alignment.

5.4. Final Acts

1. After achieving the required tolerances, fully tighten all the fastening bolts of the support legs of the units with a torque wrench to the values specified in the manufacturer's instructions. This will ensure consistency of alignment.

2. Record final alignment readings for later analysis and maintenance history.

3. Put the protective covers of the coupling in place. DANGER: Never operate equipment without guards in place.

4. Remove lock and tag (LOTO) according to internal company procedures.

6. Post-Service Inspection Checklist

After completing the alignment procedure and starting the equipment, perform the following checks.

7. Troubleshooting Guide

If you experience problems after alignment or experience unusual symptoms, please refer to the following guide.

8. Recommended Maintenance Schedule

9. Directory of Spare Parts

To ensure uninterrupted operation of the equipment, it is recommended to have the following spare parts available. All these items are available in the UNITEC electronic catalog.

Find these and other components in our E-Catalog UNITEC.

10. Links

• DSTU ISO 10816: Mechanical vibration. Evaluation of the vibration of machines on non-reactive elements with a fixed attachment.
• EN ISO 14118: Machine safety. Unexpected startup prevention.
• ISO 15243: Rolling bearings. Damages and waivers.
• EN ISO 6789: Hand-operated dynamometric tools. Requirements and test methods for verifying the conformity of the design.
• Operation and maintenance manuals from equipment and coupling manufacturers (eg Flender, KTR, SKF).
• Internal standards of the enterprise regarding safety and maintenance.