დაბალანსებული კლასიფიკაციების გაგება
ა დაბალანსების ხარისხი — also called a balance quality grade or G-კლასი — is a standardised classification that specifies how well a particular type of rotating machine must be balanced. Defined chiefly by ISO 21940-11 (the modern successor to ISO 1940-1), the grade system sorts equipment by its operating characteristics and assigns each category an appropriate ტოლერანტობის დაბალანსება. Its great value is that it gives manufacturers, maintenance technicians and end users a single, internationally recognised language for specifying and verifying rotor ბალანსის ხარისხი, so a “G6.3 pump” means the same thing in every workshop on earth.
1. The G-Grade System
Balancing grades are written as the letter “G” followed by a number — G2.5, G6.3, G16, and so on. The number is the product of the permissible residual დისბალანსი eccentricity (in millimetres) and the maximum service angular velocity (in radians per second). Put more simply, it is the permissible unbalance vibration velocity expressed in მმ/წმ — the orbital speed of the rotor’s mass centre. That single figure neatly captures the physics that matters: a grade holds the rotating ცენტრიფუგალური ძალა within bounds the machine can tolerate.
The Key Principle
Lower G-numbers mean tighter requirements — less permissible residual unbalance and smoother running. Higher G-numbers allow more residual unbalance. The system deliberately recognises that different machines have vastly different needs depending on their speed, mass, application and operating environment; there is no single “good” number, only the number appropriate to the duty.
2. Common Grades and Their Applications
ISO 21940-11 defines grades from G0.4 (highest precision) all the way to G4000 (lowest). The grades most engineers actually meet are these:
G0.4 — Ultra-High Precision
აპლიკაციები: grinding-machine spindles, gyroscopes, precision measurement equipment.
Character: needs specialised balancing equipment and a controlled environment, and is normally done in a dedicated precision დაბალანსება shop.
G1.0 — High Precision
აპლიკაციები: high-precision machine-tool spindles, turbochargers, high-speed centrifuges, computer disc drives.
Character: demands careful control of every balancing parameter and high-quality instrumentation.
G2.5 — Precision Industrial
აპლიკაციები: gas and steam turbines, rigid turbo-generator rotors, compressors, machine-tool drives, medium and large electric motors with special requirements, and centrifugal separators.
Character: the benchmark for high-quality, high-speed industrial equipment, and readily achievable with sound ველის ბალანსირება practice.
G6.3 — General Industrial (the most common grade)
აპლიკაციები: general-purpose electric motors, process-industry machinery, centrifugal pumps, fans and blowers, gear units, general machinery rotors, and medium-speed compressors.
Character: the workhorse grade for most industrial machinery, striking a good balance between achievability and performance, and comfortably within reach of portable balancing equipment.
G16 — Heavy Industrial
აპლიკაციები: drive shafts (propeller and cardan shafts), multi-cylinder diesel engines with six or more cylinders, crushers, agricultural machinery, and individual engine components.
Character: suited to robust, slower-speed equipment that tolerates more vibration.
G40 and Higher — Very Heavy Industrial
აპლიკაციები: four-cylinder diesel engines (G40), rigidly mounted slow-speed machinery, and very large, slow-turning equipment.
Character: applied to massive, slow machines where precision balance is neither economic nor technically necessary.
3. How to Select the Right Grade
Choosing a grade is a matter of weighing several factors together:
- Equipment type and design: the ISO 21940-11 tables map machine types to recommended grades and are the natural starting point.
- ოპერაციული სიჩქარე: faster machines generally need a tighter grade, because centrifugal force rises with the square of speed.
- Mounting type: equipment on flexible foundations or isolation mounts can often tolerate a higher G-number than rigidly mounted equipment.
- Proximity to people: machinery in occupied spaces may warrant a tighter grade for noise and safety.
- Special requirements: medical, precision-manufacturing and aerospace applications often demand tighter balance than standard industrial practice.
- Economics: every step to a tighter grade costs more, so the chosen grade should match operational need without over-specifying.
4. From Grade to Permissible Unbalance
The grade is the input to the calculation of the maximum permissible ნარჩენი დისბალანსი კონკრეტული როტორისთვის:
Uთითო (გ·მმ) = (9549 × გ × მ) / ბრ/წთ
- Uთითო = permissible residual unbalance, in gram-millimetres
- გ = the grade number (e.g. 6.3 for G6.3)
- M = rotor mass, in kilograms
- ბრუნები/წთ = service speed, in revolutions per minute
გამოსახული მაგალითი
Take a 100 kg fan rotor running at 1500 RPM, specified to G6.3:
Uთითო = (9549 × 6.3 × 100) / 1500 ≈ 401 g·mm
If the კორექციის სიბრტყე radius is 200 mm, that 401 g·mm corresponds to about 2.0 grams of permissible residual unbalance at that radius. The ნარჩენი არაბალანსის კალკულატორი (ISO 21940-11) performs this conversion instantly and then splits the total between two planes for you.
5. Variable-Speed and Multi-Speed Machines
When a machine runs across a range of speeds, the grade is applied with care:
- Constant-speed operation: apply the grade at the normal operating speed.
- Variable speed: apply the grade at the maximum continuous operating speed, where centrifugal forces are greatest.
- Passing through critical speeds: თვის მოქნილი როტორები, balance at the კრიტიკული სიჩქარეები may need separate attention, potentially calling for მოდალური დაბალანსება under ISO 21940-12.
6. Verification and Acceptance
Once დაბალანსება is finished, the achieved quality must be checked against the specified grade. There are two routes:
- Direct unbalance measurement: on a balancing machine, the residual unbalance is read directly and compared with Uთითო.
- ვიბრაციის გაზომვა: in field balancing, the 1× vibration amplitude serves as an indirect indicator of balance quality.
The rotor is accepted when the measured residual unbalance is at or below the calculated Uთითო, ან when the in-service vibration meets the applicable severity standard — today the ISO 20816 series (which replaced ISO 10816). On an installed machine this verification is done on-site: a portable two-channel instrument such as the ბალანსეტი-1ა ზომავს 1×-ს ამპლიტუდა და ფაზა in the machine’s own bearings at operating speed, computes the გავლენის კოეფიციენტები, applies the correction, and confirms the residual sits within the chosen grade — without removing the rotor.
7. From ISO 1940 to ISO 21940
The G-grade system was first established in ISO 1940-1, originally published in 1986. In 2016 the ISO 1940 series was revised and renumbered as the ISO 21940 series, with ISO 21940-11 replacing ISO 1940-1. The fundamental principles and grade values were carried over essentially unchanged, so older specifications remain valid, but the modern standard adds:
- Updated equipment classifications.
- Clearer guidance on grade selection.
- Better integration with the wider family of rotor-dynamics standards.
- Improved procedures for flexible rotors.
8. Common Misconceptions
“Tighter is always better”
რეალობა: over-specifying balance quality raises cost with no proportional benefit. A machine balanced to G2.5 will not necessarily outperform the same machine at G6.3 where G6.3 is the correct grade for the duty.
“Grade equals vibration level”
რეალობა: the G-number represents permissible unbalance eccentricity, not vibration amplitude. The actual ვიბრაცია a machine shows depends on many factors beyond balance — stiffness, damping, რეზონანსი, არასწორი განლაგება and looseness among them.
“One grade fits the whole plant”
რეალობა: different machine types need different grades even within one facility. A precision grinder and a crusher have wildly different balance requirements and should never share a single blanket specification.
9. Documentation and Specifications
When commissioning balancing work, the specification should state clearly:
- The required grade and standard — for example, “Balance to G6.3 per ISO 21940-11”.
- The service speed to be used for the tolerance calculation.
- The number of correction planes required.
- The verification method — shop balancing machine or field vibration measurement.
A clear, complete specification of this kind removes ambiguity and gives both the balancer and the customer a defensible record of what was required and what was achieved.
