AGMA 6014-B15

Applicability

This standard provides a method to determine the power rating ofgear sets for cylindrical grinding mills, kilns, coolers, anddryers. The formulas are applicable to steel and spheroidalgraphitic iron gears with machined spur, single helical, doublehelical, or herringbone gear teeth commonly used for this purpose.Calculations determine the allowable rating for pitting resistanceand bending strength of external spur and helical involute gearteeth.

Rating formulas

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

These rating formulas are applicable for rating the pittingresistance and bending strength of external spur and helicalinvolute gear teeth operating on parallel axes with adjustablecenter distances. The formulas evaluate gear tooth capacity asinfluenced by the major factors which affect gear tooth pitting andgear 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. Itis not intended for use by the engineering public at large.

Values for factors assigned in other standards are notapplicable to this standard nor are the values assigned in thisstandard applicable to other standards. Mixing values from otherstandards with those from this standard could lead to erroneousratings.

The gear designer or manufacturer is not responsible for thetotal system unless such a requirement is clearly identified in thecontractual agreement.

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

Where empirical values for rating factors are given by curves,curve-fitting equations are provided to facilitate computerprogramming. The constants and coefficients used in curve fittingoften have significant digits in excess of those inferred by thereliability of the empirical data. Experimental data from actualgear unit measurements are seldom repeatable within a plus or minus10 percent band. Calculated gear ratings are intended to beconservative, but the scatter in actual results may exceed 20percent.

CAUTION: Compliance with this standard does notconstitute a warranty of the rating of the gear set under installedfield service conditions.

Limitations

– Rating procedures are limited to open or semi– enclosedgearing where the gear reaction forces are transmitted through astructure which provides independent bearing support for the gearand pinion. Open gears operate without any enclosure.Semi–enclosed gears operate with a guard that provides some degreeof protection against contamination from dust or dirt and retainslubricant.

– Enclosed gear drives or speed reducers are expressly excludedfrom this standard.

– When multiple pinions are used, the number of contacts perrevolution, q, shall be the same as the number of pinions.

– Unless otherwise specified by contractual agreement, theconnected motor nameplate power including motor service factorshall be used to determine service factors as defined later withinthis standard. When not provided by the purchaser,motor servicefactor equal to 1.0 shall be used.

– This standard does not include gearing which has been surfacehardened by nitriding or flame hardening. This gear rating practiceis limited to through hardened steel and spheroidal graphitic irongears operating with through hardened, carburized, or inductionhardened steel pinions.

– Axial contact ratio of helical gear sets, mF, shall beequal to or greater than 1.0.

– Information on alignment and drive characteristics isgiven in annexes A and B.

– Formulas do not apply to external loads such as droppedcharges, electrical short circuits and earthquakes.

– Spheroidal graphitic iron data presented in the body of thestandard does not apply to austempered spheroidal graphitic iron(ADI). Rating of ADI gearing is not covered by this standard. ADIis discussed further in annex J.

– This gear rating practice is limited to maximum operatingspeeds of 2000 feet per minute gear pitch line velocity.

– This gear rating practice is limited to gears with normaldiametral pitch of 3.0 or coarser.

Exceptions

The formulas of this standard are not applicable to other typesof gear tooth deterioration such as plastic yielding, wear, casecrushing and welding. They are also not applicable when vibratoryconditions exceed the limits specified for the normal operation ofthe gears, see ANSI/AGMA 6000–B96.

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

– Damaged gear teeth;

– Spur gears with transverse contact ratio,mp, less than1.0;

– Spur or helical gears with transverse contact ratio, mp,greater than 2.0;

– Interference exists between tips of teeth and rootfillets;

– Teeth are pointed as defined by this standard, see clause7;

– Backlash is zero;

– Undercut exists in an area above the theoretical start ofactive profile;

– The root profiles are stepped or irregular, or deviate fromthe generated form. The J factor calculation uses the stressconcentration factors developed by Dolan and Broghamer [1]. Thesefactors may not be valid for root forms which are not smoothcurves. For root profiles which are stepped or irregular, otherstress correction factors may be more appropriate;

– The helix angle at the standard (reference) pitch diameter isgreater than 20 degrees for single helical and 35 degrees fordouble helical.

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

Edition:

B15

Published:

10/21/2015

ANSI:

ANSI Approved

Number of Pages:

82