AGMA 6114-B15:2015 Edition

SCOPE
Applicability

This standard provides a method to determine the power rating of gear sets with spur and helical conventional pinions and spur self-aligning pinions for cylindrical grinding mills, kilns, coolers, and dryers. The formulas are applicable to steel, ductile iron (spheroidal graphitic iron), and austempered ductile iron (ADI) with machined spur, single helical, double helical, or herringbone gear teeth. Calculations determine the allowable rating for pitting resistance and bending strength of external involute gear teeth.

Rating formulas

This standard provides a method by which different gear designs can be rated and compared. It is not intended to assure the performance of assembled gear drive systems.

These rating formulas are applicable for rating the pitting resistance and bending strength of external involute gear teeth operating on parallel axes with adjustable center distances. The formulas evaluate gear tooth capacity as influenced by the major factors which affect gear tooth pitting and gear tooth fracture at the fillet radius.

This standard is intended for use by experienced gear designers, capable of selecting reasonable values for the rating factors. It is not intended for use by the engineering public at large.

Rating formulas are valid only when components are installed according to gear manufacturer or original equipment supplier's recommendation.

Values for factors assigned in other standards are not applicable to this standard nor are the values assigned in this standard applicable to other standards. Mixing values from other standards with those from this standard could lead to erroneous ratings.

The gear designer or manufacturer is not responsible for the total system unless such a requirement is clearly identified in the contractual agreement.

It is imperative that the system designer be satisfied that the system of connected rotating parts is compatible, free from critical speeds and from torsional or other vibrations within the specified speed range, no matter how induced.

Where empirical values for rating factors are given by curves, curve-fitting equations are provided to facilitate computer programming. The constants and coefficients used in curve fitting often have significant digits in excess of those inferred by the reliability of the empirical data. Experimental data from actual gear unit measurements are seldom repeatable within a plus or minus 10 percent band. Calculated gear ratings are intended to be conservative, but the scatter in actual results may exceed 20 percent.

CAUTION: Compliance with this standard does not constitute a warranty of the rating of the gear set under installed field service conditions.

Limitations

The limitations listed below are not a comprehensive list. Additional limitations are noted within the body of this standard.

• Rating procedures are limited to open or semi-enclosed gearing where the gear reaction forces are transmitted through a structure which provides independent bearing support for the gear and pinion. Open gears operate without any enclosure. Semi-enclosed gears operate with a guard that provides some degree of protection against contamination from dust or dirt and retains lubricant.

• Completely enclosed gear drives or speed reducers are expressly excluded from this standard. For information on combination drives, see Annex J.

• When multiple pinions are used, the number of contacts per revolution of the gear, q, shall be the same as the number of pinions.

• Unless otherwise specified by contractual agreement, the connected motor nameplate power including motor service factor shall be used to determine service factors as defined in Clause 10. When not provided by the purchaser, motor service factor equal to 1.0 shall be used.

• This standard does not include gearing which has been hardened by nitriding or flame hardening.

• Axial contact ratio of helical gear sets, e_ß, shall be equal to or greater than 1.0.

• Formulas do not apply to external loads such as dropped charges, electrical short circuits and earthquakes.

• This gear rating practice is limited to a maximum pitch line velocity of 10.16 meters per second.

• This gear rating practice is limited to gears with module of 8 to 50.

• Helical self-aligning pinions are beyond the scope of this standard.

Exceptions

The formulas of this standard are not applicable to determine rating capacity for other types of gear tooth deterioration such as plastic deformation, adhesive or abrasive wear, subcase fatigue, and scuffing. They are also not applicable when vibratory conditions exceed the limits specified for the normal operation of the gears, see ANSI/AGMA 6000.

The formulas of this standard are not applicable when any of the following conditions exist:

• damaged gear teeth;

• spur gears with transverse contact ratio, e_a, less than 1.0;

• spur or helical gears with transverse contact ratio, e_a, greater than 2.0;

• interference exists between tips of teeth and root fillets;

• teeth are pointed as defined by this standard, see Clause 7;

• backlash is zero;

• undercut exists in an area above the theoretical start of active profile;

• the root profiles are stepped or irregular, or deviate from the generated form. The Y_J factor calculation uses the stress concentration factors developed by Dolan and Broghamer [1]. These factors may not be valid for root forms which are not smooth curves. For root profiles which are stepped or irregular, other stress correction factors may be more appropriate;

• the helix angle at the standard (reference) pitch diameter is greater than 20 degrees for single helical and 35 degrees for double helical.

Fractures emanating from stress risers on the tooth profile, tip chipping, and failures of the gear blank through the web or rim should be analyzed by general machine design methods.

FOREWORD

[The foreword, footnotes and annexes, if any, in this document are provided for informational purposes only and are not to be construed as a part of AGMA Standard 6114-B15, Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment (Metric Edition).]

This standard presents formulas and information using ISO symbology and SI units.

AGMA 321.01 was originally developed to cover gears used primarily for ball and rod mills, and for kilns and dryers. It was approved in October 1943, and later modified in June 1946. In June 1951, AGMA 321.03 was approved as a standard. Further changes and additions were approved in June 1959, and AGMA 321.04 was issued in March 1960. AGMA 321.05 was approved in March 1968 and issued in March 1970.

In February 1979, the Mill Gearing Committee was reorganized to review AGMA 321.05 and revise it in accordance with AGMA 218.01, Rating the Pitting Resistance and Bending Strength of Spur and Helical Involute Gear Teeth. With AGMA 218.01 as a guide, the committee submitted the first draft of ANSI/AGMA 6004-F88 in March 1984.

ANSI/AGMA 6004-F88 superseded AGMA 321.05, Design Practice for Helical and Herringbone Gears for Cylindrical Grinding Mills, Kilns, Coolers, and Dryers. It was approved by the AGMA membership in January 1988 and approved as an American National Standard on May 31, 1988.

ANSI/AGMA 6004 was not widely accepted by the industry and many continued to use AGMA 321.05. As such, the AGMA Mill Gearing Committee began work on ANSI/AGMA 6114-A06 in November 2001. Changes to the standard include a new dynamic factor analysis as a function of transmission accuracy number, revised allowable stress numbers, the use of the stress cycle factor in the rating practice, and ratings for gears made from ductile iron. Extensive discussions on new equipment installation and alignment, lubrication, and use of ausferritic ductile iron (ADI) were added to the annex.

The AGMA Mill Gearing Committee began work on AGMA 6114-B15 in February 2011. Changes to the standard, based on committee experience and field performance of gear sets, include:

• added load distribution factor for self-aligning pinions;

• modified values of s_FP for ductile iron and ADI;

• reformatted graph of minimum effective case depth for carburized and induction hardened pinions, h_{e min};

• moved austempered (formerly ausferritic) ductile iron from Annex H to the body of the standard;

• revised Annex D to include information taken from ANSI/AGMA 9005-E02 [8];

• changed references to extreme pressure (EP) additives to antiscuff (AS) additives in Annex D. Users are encouraged to transition their terminology away from the term extreme pressure, or EP, and toward antiscuff, or AS;

• updated material mechanical property information in Annex F;

• added Annex J to provide information on combination drives.

Values for factors assigned in other standards are not applicable to this standard, nor are the values assigned in this standard applicable to other standards. The ability to design gears, and the knowledge and judgment required to properly evaluate the various rating factors comes primarily from years of accumulated experience in gearing. The detailed treatment of the general rating formulas for specific applications is best accomplished by those experienced in the field.

The first draft of AGMA 6114-B15 was made in September 2012. It was approved by the AGMA membership in August 2015 and approved as an American National Standard on October 21, 2015.

Published Code	AGMA
Published By	American Gear Manufacturers Association
Publication Date	2015
Pages Count	82
Language	English
File Size	2.0 MB
ISBN	9781555890476