ISO 10816-3: Mechanical vibration – Evaluation of machine vibration by measurements on non-rotating parts – Part 3: Industrial machines

Summary

ISO 10816-3 is a widely used, practical standard that provides specific numerical limits for vibration severity on common industrial machines. It is the direct application of the general framework established in ISO 10816-1. While Part 1 explains *how* to measure and evaluate vibration in general, Part 3 provides the actual numbers—the RMS velocity values—that define the boundaries for the “Good,” “Satisfactory,” “Unsatisfactory,” and “Unacceptable” evaluation zones for specific groups of machines.

Note: This standard has been formally replaced by ISO 20816-3, which updates the framework but the core principles and many of the limit values remain highly relevant.

Table of Contents (Conceptual Structure)

The standard is structured to provide a clear, actionable guide for assessing the vibration of a specific machine:

1. 1. Scope:

   This initial section specifies the types of machinery for which this standard is applicable. It is designed to be a practical guide for the most common industrial machines, such as centrifugal pumps, electric motors, compressors, and fans, with power ratings above 15 kW and operating at speeds between 120 RPM and 15,000 RPM. It explicitly states that it applies to measurements taken on the non-rotating parts (e.g., bearing housings) under normal steady-state operating conditions. It also clarifies which machine types are excluded, such as reciprocating machinery and machine tools, which are covered by other specific standards.

2. 2. Machine Classification (Groups):

   This section is fundamental to the correct application of the standard, as it divides industrial machines into four distinct groups based on three key factors: power rating, foundation type, and mounting characteristics. The classification is critical because machines in different groups are allowed different vibration limits. The four groups are:

   • Group 1: Large machines with power ratings above 300 kW, typically mounted on rigid, heavy foundations (such as concrete pads). These machines include large pumps, compressors, and generators. Due to their size and rigid mounting, they are expected to have very low vibration levels.
   • Group 2: Medium-sized machines with power ratings between 15 kW and 300 kW, also mounted on rigid foundations. This group covers the majority of common industrial equipment, including most electric motors, medium-sized pumps, and fans. The vibration limits for this group are higher than Group 1 but still quite restrictive.
   • Group 3: Large machines with power ratings above 300 kW, but mounted on flexible or soft foundations (such as spring isolators or rubber mounts). The flexible mounting allows higher vibration levels without transmitting forces to the surrounding structure.
   • Group 4: Medium-sized machines (15 kW to 300 kW) on flexible foundations. This group has the most lenient vibration limits, as the combination of moderate size and flexible mounting allows for higher acceptable vibration levels.

   The distinction between rigid and flexible foundations is crucial for proper classification. A rigid foundation transmits vibration directly to the surrounding structure, while a flexible foundation isolates the machine vibration from its surroundings.

3. 3. Vibration Severity Zone Values (The Chart):

   This section contains the numerical heart of the standard—the specific RMS velocity values (in mm/s) that define the boundaries between the evaluation zones for each machine group. The standard presents this information in tabular format, providing clear, actionable limits for condition assessment. For example, typical values might include: Group 1 machines having an A/B boundary at 0.71 mm/s and a B/C boundary at 1.8 mm/s, while Group 4 machines might have an A/B boundary at 1.8 mm/s and a B/C boundary at 4.5 mm/s. These numerical values are the result of decades of empirical data collection from industrial machinery worldwide. The chart also includes equivalent values in inch/second units for regions that use imperial measurements, ensuring global applicability of the standard.

4. 4. Guidance on Application:

   This final section provides essential practical guidance on how to properly apply the zone values in real-world situations. It distinguishes between two primary applications: acceptance testing and operational monitoring. For acceptance testing of new, newly installed, or freshly repaired equipment, the standard recommends that vibration levels should normally fall within Zone A (for the smoothest machines) or Zone B (for acceptable machines). Any new equipment exhibiting Zone C vibration levels should be investigated and corrected before being put into service. For operational monitoring of machines already in service, the standard acknowledges that some machines may operate acceptably in Zone B, but emphasizes that any movement from a lower zone to a higher zone (such as from Zone B to Zone C) is a significant change that warrants immediate investigation. The section also provides guidance on measurement procedures, emphasizing the importance of taking measurements at the bearing locations in three orthogonal directions (horizontal, vertical, and axial) and using the highest reading for evaluation.

Key Concepts

• Actionable Limits: This standard’s primary value is that it translates the theoretical framework of Part 1 into concrete, numerical limits. It provides the basis for setting alarms on monitoring systems and for making pass/fail decisions on new equipment.
• Importance of Machine Grouping: A vibration level that is perfectly acceptable for a large, flexibly mounted fan (Group 3) could be a sign of imminent failure for a medium-sized, rigidly mounted motor (Group 2). Correctly classifying the machine is the essential first step.
• Broadband Screening Tool: Like its parent standard, ISO 10816-3 is based on a single broadband RMS velocity measurement. It is designed to identify *that* a problem exists but does not provide the diagnostic information to determine the root cause. For that, spectral analysis is required.

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