Standards

Mechanical Vibrations - Balance Quality Requirements for Rotors in a Constant (Rigid) State - Part 1: Specification and Verification of Balance Tolerances

Summary

ISO 1940-1:2003 provides specifications for rotors in a rigid (constant) state. It defines balancing tolerances, the number of correction planes required, and methods for verifying residual unbalance.

Recommendations are also given regarding the balance quality of rigid rotors according to their type and maximum operating speed. These recommendations are based on worldwide practical experience.

ISO 1940-1:2003 also aims to facilitate the relationship between manufacturers and users of rotating machinery by defining acceptance criteria for the verification of residual unbalance.

Additional information concerning errors associated with balancing and residual unbalance determination is provided in ISO 1940-2.

ISO 1940-1:2003 does not apply to flexible rotors. Quality criteria for rotors balanced in a flexible state are defined in ISO 11342.

Balance quality grades for various representative groups pf rigid rotors

G 4000

• Crankshaft drives (3) of slow-speed marine diesel engines (4), rigidly mounted, with an odd number of cylinders

G 1600

• Crankshaft drives, rigidly mounted, of large two-stroke engines

G 530

• Crankshaft drives, rigidly mounted, of large four-stroke engines
• Crankshaft drives, elastically mounted, of marine diesel engines

G 250

• Crankshaft drives, rigidly mounted, of high-speed diesel engines (4) with four cylinders

G 100

• Crankshaft drives of high-speed diesel engines (4) with six cylinders or more
• Complete engines (5) (gasoline or diesel) for cars, trucks and locomotives

G 40

• Passenger car wheels, wheel rims, wheel assemblies, drive shafts
• Crankshaft drives, elastically mounted, of high-speed four-stroke engines (gasoline or diesel) with six cylinders or more
• Crankshaft drives of engines for cars, trucks and locomotives

G 16

• Drive shafts (propeller shafts, cardan shafts) with special requirements
• Components of crushing and grinding machines
• Agricultural machinery components
• Replacement engine parts (gasoline or diesel) for cars, trucks and locomotives
• Crankshaft drives of engines with six cylinders or more under special operating conditions

G 6.3

• Components of processing machinery
• Main marine turbine gears (merchant shipping)
• Centrifuge drums
• Paper machine rolls; printing machine rolls
• Fans
• Rotor assemblies with aircraft gas turbines
• Flywheels
• Pump impellers
• General machine tools and machine components
• Large and medium-size electrical armatures (electric motors with shaft height of at least 80 mm) without special requirements
• Small electrical armatures produced in large series for vibration-insensitive applications and/or with vibration-isolated supports
• Engine spare parts with special requirements

G 2.5

• Gas and steam turbines, including main marine turbines (merchant shipping)
• Rigid turbogenerator rotors
• Computer memory drums and disks
• Turbochargers
• Machine tool drives
• Large and medium-size electrical armatures with special requirements
• Small electrical armatures not meeting one or both conditions specified for small electrical armatures of balance quality grade G 6.3
• Turbine-driven pumps

G 1

• Tape recorder and phonograph (gramophone) drives
• Grinding wheel drives
• Small electrical armatures with special requirements

G 0.4

• Precision grinding spindles, disks and armatures
• Gyroscopes

Notes

(3) A crankshaft drive assembly includes the crankshaft, flywheel, clutch, pulley, vibration damper, rotating parts of the connecting rod, etc.

(4) In this part of ISO 1940, slow-speed diesel engines are defined as having a piston speed below 9 m/s, while high-speed diesel engines have a piston speed above 9 m/s.

(5) For complete engines, the rotor mass includes the sum of all masses belonging to the crankshaft drive assembly described in Note 3 above.

Permissible vibration levels for rotating machines

Group 1: Parts of machines or engines that are, under normal operating conditions, integral with the complete machine. (Mass-produced electric motors up to 15 kW are typical examples of this group.)

Group 2: Medium-sized machines, particularly electric motors with power outputs between 15 and 75 kW, without special foundations. Rigidly mounted motors or machines (up to 300 kW) installed on special foundations.

Group 3: Large machines and other heavy machinery with rotating masses mounted on rigid, heavy foundations that are relatively stiff in the direction of vibration.

Group 4: Large machines and other heavy machinery with rotating masses mounted on foundations that are relatively flexible in the direction of vibration (e.g., turbo-generator sets, particularly those installed on lightweight foundations).