Dynamic balance test

Dynamic Balance Testing Service – Accredited ISO/IEC 17025 Rotating Equipment Performance Assessment for the Colombian Market

Dynamic balance is a critical parameter for rotating machinery, components, and assemblies used in a wide range of industries, including power generation, oil and gas, mining, automotive, aerospace, marine, and industrial manufacturing. Unbalance in rotating elements such as turbines, compressors, fans, pumps, motors, shafts, and flywheels can cause excessive vibration, premature bearing wear, noise, reduced efficiency, and catastrophic failure. In the Colombian market, where the Superintendencia de Industria y Comercio (SIC), the Ministerio de Minas y Energía (MinMinas), the Agencia Nacional de Hidrocarburos (ANH), and the Dirección de Impuestos y Aduanas Nacionales (DIAN) enforce strict quality and safety standards for rotating equipment, the accurate evaluation of dynamic balance is essential for product certification, quality control in manufacturing, field balancing, and import-export processes. Our laboratory offers a comprehensive dynamic balance testing service, applying standardized methods that measure residual unbalance, determine correction weights and angles, and verify the balance quality grade (G) according to ISO 1940-1. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Colombian authorities, making them indispensable for regulatory compliance, equipment reliability, and market access in Colombia.

Rotating Components We Regularly Test

Our laboratory receives a wide variety of rotating components and assemblies for dynamic balance testing. Typical samples include:

• Turbine rotors – steam turbines, gas turbines, and hydro turbines for power generation.
• Compressor and pump impellers – centrifugal compressors, axial compressors, and centrifugal pumps.
• Fan and blower assemblies – industrial fans, HVAC fans, and cooling fans.
• Motor and generator rotors – electric motor armatures and generator rotors for a variety of applications.
• Shafts and transmission components – drive shafts, propeller shafts, and coupling assemblies.
• Flywheels and energy storage rotors – for uninterruptible power supplies and regenerative braking systems.
• Grinding and machining spindles – for machine tools, grinding wheels, and polishing heads.
• Prototype and newly manufactured rotors – submitted by manufacturers for balance validation before series production.
• Rotors retrieved from field service – for balance re-certification and condition assessment.

Dynamic Balance Testing – Principles and Measurement

Dynamic balance testing is performed on a balancing machine that measures the magnitude and angular position of the unbalance forces in rotating components. Our tests are based on the ISO 1940-1 standard, which defines the balance quality grades (G) for various applications, from G 0.4 (precision gyroscopes) to G 4000 (crankshafts of slow engines).

• Dynamic balance test – two-plane balancing (ISO 1940-1 / NTC 7000) – the rotating component is mounted on a balancing machine (soft-bearing or hard-bearing type). It is accelerated to a specified test speed (typically the service speed or a speed close to the service speed). The unbalance forces are measured in two correction planes using force transducers or vibration sensors. The amplitude and phase angle of the unbalance are calculated, and the correction mass and its angular position are determined. We report the initial unbalance (in g·mm or g·mm per plane), the residual unbalance after correction, and the balance quality grade (G) achieved.
• Single-plane balancing (static balancing) – ISO 1940-1 / NTC 7001 – for components with a low length-to-diameter ratio (e.g., discs, flywheels, pulleys), we perform single-plane balancing. The component is mounted on a balancing machine with a single correction plane. The unbalance is measured, and a correction mass is added to bring the component into balance. We report the residual unbalance and the balance quality grade.
• Balancing at different speeds (NTC 7002 – speed effect on balance) – we perform the dynamic balance test at multiple speeds (e.g., 50 %, 75 %, and 100 % of the service speed) to evaluate the speed dependence of the unbalance and to ensure that the balance is maintained across the operating speed range. We report the unbalance values at each speed.
• Balancing of flexible rotors (ISO 11342 / NTC 7003 – for rotors operating above their first critical speed) – for flexible rotors that deform at their critical speeds, we apply a modal balancing approach, which involves balancing at multiple speeds and using multiple correction planes. We report the modal unbalance components and the balance quality grade.
• Balance tolerance and grade verification (NTC 7004 – acceptance criteria) – based on the measured residual unbalance and the rotor mass, we calculate the specific unbalance (e) and compare it with the tolerance limits specified by ISO 1940-1 for the intended application. We report the acceptance (pass/fail) and the specific unbalance.

Correction Methods – Achieving the Required Balance Quality

After the unbalance is measured, the rotor is corrected by adding or removing mass in the correction planes. Our laboratory provides guidance on the optimal correction method and verifies the balance quality after correction.

• Addition of correction weights (NTC 7010 – weld-on, screw-on, or adhesive weights) – we provide correction weights of specified mass and geometry (e.g., washers, clips, or plates) that are added to the rotor at the calculated angular positions. The weights are secured by welding, screwing, or adhesives. We verify the balance after weight installation and report the final unbalance.
• Removal of material (NTC 7011 – grinding, drilling, or machining) – for rotors where material removal is preferred (e.g., for aesthetic reasons or to avoid adding protrusions), we identify the locations where material should be removed (by drilling, grinding, or machining) to achieve the balance. We verify the balance after removal and report the final unbalance.
• Balancing of assembled components (NTC 7012 – field balancing) – for large or assembled components (e.g., fans with their blades, turbine rotors with their blading), we perform the balance on the complete assembly. The unbalance is measured, and correction weights are added to the assembly. We report the unbalance and the balance quality grade of the assembly.
• Balancing with high-speed correction (NTC 7013 – correction at service speed) – for rotors that operate at high speeds, we perform the correction at the service speed, using the same balancing machine, to ensure that the balance is accurate at the operating speed. We report the unbalance at service speed.
• Influence coefficient method (NTC 7014 – for multi-plane balancing) – for complex rotors (e.g., with multiple correction planes or asymmetrical geometry), we use the influence coefficient method to calculate the required corrections. The method involves measuring the effect of trial weights in each correction plane and solving for the optimal correction masses. We report the influence coefficients and the final balance quality.

Vibration Analysis and Condition Monitoring – Assessing the Overall Health of Rotating Equipment

Dynamic balance is closely linked to vibration levels. Our vibration analysis complements the balance test by evaluating the overall mechanical condition of the rotor and its supporting bearings, and it can help diagnose other issues such as misalignment, bearing wear, or looseness. This service is critical for predictive maintenance and for identifying the root cause of excessive vibration.

• Vibration measurement during balance test (ISO 10816 / NTC 7020 – for machine condition assessment) – during the dynamic balance test, we measure the vibration levels (velocity, displacement, or acceleration) at the bearing caps using accelerometers or velocity sensors. We report the vibration velocity (in mm/s) and compare it with the ISO 10816-3 limits (or other applicable standards) for the equipment category.
• Order tracking and spectral analysis (NTC 7021 – for identifying vibration sources) – we perform order tracking (FFT analysis) on the vibration signal to identify the dominant frequencies and to distinguish between 1× (unbalance) and higher-order components (misalignment, bearing faults, or looseness). We report the vibration spectrum and the amplitude at the 1× frequency.
• Bearing condition monitoring (NTC 7022 – vibration envelope and acceleration analysis) – for rolling element bearings, we use envelope analysis or acceleration measurements to detect early bearing faults (e.g., spalling, fatigue) that may cause vibration even if the rotor is balanced. We report the bearing condition index and the presence of any fault frequencies.
• Phase analysis (NTC 7023 – for diagnosing unbalance and misalignment) – we measure the phase angle of the vibration signal at different positions on the rotor to distinguish between unbalance (0° phase shift) and misalignment (180° phase shift). We report the phase angles and the diagnosis.
• Resonance testing and modal analysis (NTC 7024 – for avoiding critical speeds) – we perform a frequency sweep or impact test to identify the natural frequencies (critical speeds) of the rotor, to ensure that the service speed is sufficiently away from any resonance. We report the natural frequencies and the damping ratios.

On-Site and Field Balancing – Balancing Equipment in Service

For large equipment that cannot be transported to the laboratory, or for machinery that is already installed in the field, we offer on-site dynamic balancing services. Our portable balancing equipment allows us to perform dynamic balance tests and corrections directly at the installation site, minimizing downtime.

• Field balancing of industrial fans and blowers (NTC 7030 – in-situ balancing) – we perform dynamic balance testing and correction on installed fans and blowers, using portable vibration analyzers and field balancing software. The rotor is run at its service speed, and the unbalance is measured using a tachometer and accelerometers. Correction weights are calculated and installed on the fan blades or hub. We report the initial and final vibration levels and the balance quality grade.
• Field balancing of large motors and generators (NTC 7031 – in-situ motor balancing) – for large motors and generators, we perform field balancing on the rotor while it is installed in its bearings. The balancing is performed at the operating speed, and correction weights are added to the rotor. We report the initial and final vibration levels and the balance quality grade.
• Field balancing of centrifugal pumps and compressors (NTC 7032 – pump balancing) – for pumps and compressors with impellers, we perform in-situ balance tests by adding trial weights to the impeller or shaft. We report the initial and final vibration levels and the balance quality grade.
• Field balancing of turbines and turbo-generators (NTC 7033 – on-site turbine balancing) – for large turbines and turbo-generators, we perform multi-plane balancing using portable balancing equipment. The balancing is performed at the operating speed. We report the unbalance corrections and the final vibration levels.
• Post-balance performance verification (NTC 7034 – acceptance testing after balancing) – after the field balancing, we run the equipment at full speed and measure the vibration levels to confirm that the balance quality grade is achieved. We report the final vibration levels and the pass/fail status.

Complementary Tests – Mechanical and Dimensional Inspections

To ensure the integrity of the rotor and to identify any factors that may affect the balance, we complement the dynamic balance tests with mechanical and dimensional inspections, which are essential for quality control and for ensuring the long-term reliability of the equipment.

• • Dimensional inspection of the rotor (NTC 7040 – runout and concentricity measurement) – we measure the radial and axial runout of the rotor shaft using dial indicators, to detect any bending, ovality, or out-of-concentricity that could affect the balance. We report the runout values and the locations of any deviations.
  • Hardness testing (ASTM E18 / NTC 7041 – for material strength) – we measure the hardness of the rotor shaft and the rotor body to verify the mechanical strength and to detect any localized softening or hardening that may indicate damage or material defects. We report the hardness values.
  • Non-destructive testing (NDT – NTC 7042 – ultrasonic and magnetic particle inspection) – we perform ultrasonic testing (UT) on the rotor shaft to detect internal defects (cracks, inclusions), and magnetic particle inspection (MPI) on the surface to detect surface cracks. We report the NDT results and the locations of any defects.
  • Surface inspection for damage or contamination (NTC 7043 – visual and microscopic) – we inspect the rotor surface for signs of wear, pitting, corrosion, or contamination (e.g., deposits of grease or scale) that could cause unbalance. We report the observations and the condition of the rotor surface.
  • Key and slot inspection (NTC 7044 – for fit and alignment) – we inspect the keyways and slots on the rotor shaft for proper fit and alignment, as a loose key or a damaged keyway can cause unbalance. We report the condition and the fit of the key.

Test Report and Recognition in the Colombian Industrial and Energy Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with balancing machines and vibration analyzers calibrated periodically using reference rotors and traceability to international standards (NIST, PTB). Our test reports are issued in Spanish and include:

• Full identification of the rotating component (manufacturer, model, serial number, mass, diameter, speed, and application).
• Detailed description of the test methods applied (ISO 1940-1/NTC standards, balancing speed, correction planes, and type of balancing machine).
• Numerical results: initial and residual unbalance (g·mm), correction mass (g), angular position of the correction weight (°), specific unbalance (e, g·mm/kg), balance quality grade (G), vibration velocity (mm/s), and pass/fail status.
• Graphical data: unbalance polar plots, vibration spectra, and runout profiles.
• Comparative tables against the values specified by the client or against the limits of the ISO 1940-1 and NTC 7000 for the specific balance quality grade.
• Photographs of the rotor, the balancing setup, the correction weights, and the final balanced assembly.
• Recommendations for maintenance, for periodic re-balancing, and for corrective actions to prevent unbalance (e.g., cleaning, alignment, or bearing replacement).
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98-3 Guide.

These reports are fully accepted by the Superintendencia de Industria y Comercio (SIC) for product registration and quality certification, by the Ministerio de Minas y Energía (MinMinas) and the Agencia Nacional de Hidrocarburos (ANH) for the verification of rotating equipment used in oil, gas, mining, and power generation, and by the Dirección de Impuestos y Aduanas Nacionales (DIAN) for tariff classification and quality verification in the import of rotating machinery. Additionally, we offer consulting services for the design of rotating components with optimal balance, the selection of balancing methods, and the implementation of predictive maintenance programs for rotating equipment, contributing to the safety, reliability, and efficiency of industrial operations in the diverse and growing Colombian market, from the Caribbean refineries to the Andean power plants and mining facilities.