GB/T 9239 Mechanical vibration - Rotor balancing consists of the following parts:
——Part 1: Introduction );
——Part 2: Vocabulary );
——Part 11: Procedures and tolerances for rotors with rigid behaviour );
——Part 12: Procedures and tolerances for rotors with flexible behaviour );
——Part 13: Criteria and safeguards for the in-situ balancing of medium and large rotors );
——Part 14: Procedures for assessing balance errors );
——Part 21: Description and evaluation of balancing machines );
——Part 23: Enclosures and other protective measures for balancing machines );
——Part 31: Susceptibility and sensitivity of machines to unbalance );
——Part 32: Shaft and fitment key convention ).
This part is Part 32 of GB/T 9239.
This part is drafted in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 16908-1997 Mechanical vibration - Balancing - Shaft and fitment key convention, the following technical changes have been made with respect to GB/T 16908-1997:
——The standard name is modified;
——Three terms defined in the former standard are deleted (see 3.1~3.3 of Edition 1997).
——Annex B “Transitional countermeasures for half-key convention” is deleted (see Annex B of Edition 1997).
This part, by means of translation, is identical to ISO 21940-32:2012 Mechanical vibration - Rotor balancing - Part 32: Shaft and fitment key convention.
The Chinese document identical to the normative international document given in this part is as follows:
——GB/T 6444-2008 Mechanical vibration - Balancing vocabulary (ISO 1925:2001, IDT).
This part was proposed by and is under the jurisdiction of the Mechanical Vibration Shock and Condition Monitoring (SAC/TC 53).
The previous edition replaced by this part is as follows:
——GB/T 16908-1997.
Introduction
It is often impossible or economically unreasonable to balance rotors with fitments after they have been assembled; the rotor components which also may originate from different suppliers are therefore balanced separately. An appropriate balance tolerance is applied to each component so that, when shaft and fitment(s) are coupled together, the rotor assembly meets the required balance tolerance and/or vibration limit. If, however, a different key convention has been used when balancing the shaft than that one used for balancing the fitment(s), it is quite likely that the rotor assembly has a balance error influencing its residual unbalance.
There are three methods, or key conventions, for balancing shafts and fitments coupled together with keys:
——full-key convention;
——half-key convention;
——no-key convention.
ISO 21940-32 adopted in this part unifies the key conventions used throughout the world and gives instructions on a marking of components balanced in accordance with the key convention applied. When consistently used, it results in compatibility of shafts and fitments so that they can be balanced by different suppliers and, after being assembled, the balance tolerance and/or vibration limit for the rotor assembly is met.
Mechanical vibration - Rotor balancing - Part 32: Shaft and fitment key convention
1 Scope
This part of GB/T 9239 specifies one convention for balancing the individual components (shaft and fitments) of a keyed rotor assembly. This provides compatibility of all balanced components so that when they have been assembled the overall balance tolerance and/or vibration limit for the rotor assembly is met.
This part specifies that half-keys be used when balancing the individual components of a keyed rotor assembly. It also specifies a marking of the components balanced in accordance with the key convention used.
This part applies to rotors balanced in a balancing machine, in their own bearings or in situ. The key convention can also be applied when measuring the residual unbalance and/or vibration of rotors with keyways, but to which fitments have not yet been assembled.
In addition to applying to keys of constant rectangular or square cross-section mounted parallel to the shaft centreline, this part also applies to keys mounted on tapered shaft surfaces, to woodruff, taper, dowel and other special keys. The principle of the half-key convention is applied as is appropriate to the particular shape and location of the special key.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including having amendments) applies to this document.
ISO 1925 Mechanical vibration - Balancing - Vocabulary )
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1925 apply.
4 Half-key convention
This part specifies that the half-key convention be followed. According to this convention, a half-key shall be used in the keyway of the shaft having one keyway while balancing the shaft without the fitment. A complementary half-key shall be used while balancing the corresponding fitment on a balancing mandrel, provided the mandrel has no keyways. If the mandrel has keyways, the methods described in A.1.3 shall be followed. If at one cross-section, shaft and fitment each have two keyways the methods described in A.1.4 shall be followed. The axial location of the centre of gravity of the half-key should be the same as that of the full key in the final assembly.
Note: Table 1 shows examples of various types of shaft keyways and full keys of constant rectangular or square cross-section.
Practical considerations for making and usage of half-keys are given in Annex B. A contoured half-key set is shown in Figure 1.
The use of the half-key convention provides a uniform method for balancing shafts and fitments joined together by keys. It eliminates balance errors and therefore unnecessary residual unbalance and/or vibration which can be caused by the use of different key conventions, and avoids the creation of an internal bending moment in the assembly (as would be caused by the use of full keys during balancing of the shaft). For more information on the differences between the key conventions, see Annex C.
Table 1 Examples of types of shaft keyways and keys
Type Configuration of keyway Name of keyway Configuration of key a Name of key
A Round/round end Square/square end
Round/round end
B Round/square end Round/square end
Square/square end
Round/round end
C Sled runner Square/square end
l——length of the keyway;
d——depth of the keyway.
Key:
1——half-key for the fitment;
2——half-key for the shaft.
Figure 1 Contoured half-key set
5 Mark
5.1 The end face of the shaft adjacent to the keyway shall be permanently marked with the letter H to indicate that balancing was performed using the half-key convention. Permanent marking using metal stamps or vibratory engravers is recommended, but a permanent or indelible ink may also be used.
If the shaft end face is too small for marking, the bottom of the keyway may be used.
5.2 The face of the fitment adjacent to the keyway shall be permanently marked with the letter H to indicate that balancing was performed using the half-key convention. The letter should be readily visible when the fitment is joined to the shaft. Permanent marking using metal stamps or vibratory engravers is recommended, but a permanent or indelible ink may also be used.
5.3 The marking of the shaft and the fitment with the letter H may only be omitted if confusion as to which key convention was used is unlikely.
5.4 When balancing a replacement shaft or fitment, the known mating part of which has not been balanced using the half-key convention, it is permissible to balance the replacement component with the key convention of the existing mating part. In this special case, both components shall be permanently marked with an identification letter corresponding to the key convention used, as follows:
a) components balanced using the full-key convention (see C.1.2) shall be marked with the letter F adjacent to the keyway;
b) components balanced using the no-key convention (see C.1.4) shall be marked with the letter N adjacent to the keyway.
Note 1: For the fitment, the balancing procedures in accordance with the full-key convention and the no-key convention are identical. Marking is done as ordered.
Note 2: If fitments are balanced for being put on stock, these fitments may be marked either with F or with N. But since the full-key convention is in use more often, these fitments generally are marked with F.
6 Implementation of the half-key convention
All manufacturers of original parts and processed components shall comply with the half-key convention of balancing and mark each newly manufactured shaft and fitment with the letter H.
Note: Some International Standards prescribe that the half-key convention be followed, e.g. IEC 60034-14 [1].
Change-over of equipment in service to the half-key convention with proper marking of the shaft and fitment(s) during a repair balancing operation is encouraged. In any case, a marking shall be added (see Clause 5).
Foreword i
Introduction iii
1 Scope
2 Normative references
3 Terms and definitions
4 Half-key convention
5 Mark
6 Implementation of the half-key convention
Annex A (Informative) Specifications for the half-key convention
Annex B (Informative) Practical considerations for making half-keys and usage of keys
Annex C (informative) Comparison between shaft and fitment key conventions
Bibliography
