AGMA 6011 vs API 613 vs API 677: Which Standard Does Your High-Speed Gearbox Need?

ANSI/AGMA 6011 is the general specification for high-speed helical gear units, triggered by pitch-line velocity or shaft speed. API 613 and API 677 are petroleum, chemical and gas industry standards: API 613 is for special-purpose units in continuous service with no installed spare, and API 677 is for general-purpose units. Specify API 613 only when the service is genuinely critical, because it is the most conservative rating basis and over-specifying it adds size, cost and some high-speed operating risk.

What does each standard actually cover?

Each standard answers a different question: AGMA 6011 asks “is this a high-speed unit?”, while API 613 and API 677 ask “how critical is this unit to a petroleum, chemical or gas process?” The table below summarizes the scope of each as published by the standards bodies and their resellers.

Standard	Current edition	Scope (paraphrased)	Typical use
ANSI/AGMA 6011-J14 (reaffirmed 2019)	J14, approved 2014	Single and double helical, parallel-shaft speed reducers and increasers where at least one stage runs at a pitch-line velocity of 35 m/s or more, or above 4,500 rpm, with other stages at 8 m/s or more. Covers design, lubrication, bearings, testing and rating.	High-speed industrial service, test stands, dynamometers, turbine and compressor drives outside API-mandated specs
API Std 613	6th edition, July 2021	Special-purpose, enclosed, precision single and double helical one- and two-stage parallel-shaft increasers and reducers for continuous service without installed spare equipment. Includes lube systems, controls and instrumentation.	Critical, unspared trains in refineries, gas processing and petrochemical plants
API Std 677	4th edition, September 2021	General-purpose, extruder and epicyclic enclosed gear units with parallel-shaft spur and helical gears. Extruder gears limited to 60 m/s (12,000 ft/min) pitch-line velocity. Excludes special-purpose and integral gears.	Spared or lower-criticality petroleum, chemical and gas service
ANSI/AGMA 6013-B16	B16	Industrial enclosed gear drives: design, rating, lubrication, testing and selection. Applies below 35 m/s pitch-line velocity.	Standard industrial reducers and increasers

API 613 also states what it does not cover: general-purpose gear units (the territory of API 677), integrally geared compressors, and non-involute gearing.

How do you know if your gearbox counts as “high-speed”?

Calculate the pitch-line velocity of the fastest mesh. If any stage reaches 35 m/s (roughly 6,900 ft/min) or any shaft exceeds 4,500 rpm, AGMA 6011 is the applicable AGMA specification rather than the industrial drive standard.

Pitch-line velocity in ft/min is 0.2618 × pitch diameter (in) × rpm. A 6-inch pinion at 6,000 rpm gives 0.2618 × 6 × 6,000 ≈ 9,400 ft/min, or about 48 m/s. That unit is high-speed by AGMA’s definition even if the power is modest. Many test-stand speed increasers cross this line at a few hundred horsepower, which is why speed, not size, decides the standard.

When does API 613 apply?

API 613 applies when the gear unit sits in a petroleum, chemical or gas process, runs continuously and has no installed spare, so a gear failure shuts down production. Typical examples are main compressor, pump or generator drives on a process train.

The standard’s value is in its total package. It covers not only the gear rating but the lubricating system, controls, instrumentation and auxiliary equipment, which is what a refinery reliability engineer wants for a machine that cannot be bypassed. In practice, many owners also apply procurement supplements: in 2020 the IOGP’s JIP33 program published S-713 (special-purpose gear units, aligned with API 613) and S-712 (general-purpose gear units, aligned with API 677) to standardize purchaser requirements on top of the API documents. Note that those supplements were written against API 613 5th edition and API 677 3rd edition, so check edition alignment if your project references both.

When is API 677 the right call?

API 677 fits petroleum, chemical and gas service where the unit is general-purpose: spared, intermittent, or not critical to the process. It also covers extruder gears and epicyclic gears for equipment such as generators, centrifugal compressors and pumps.

Since its second edition in 1997, API 677 has used the API 613 rating method, according to a 2016 Turbomachinery Magazine analysis by gear engineer John M. Rinaldo. The tooth rating is therefore similarly conservative; the difference lies mainly in the scope of auxiliary systems, documentation and inspection that the purchaser can call for. For a spared pump drive in a plant that mandates API equipment, API 677 usually gives the compliance the owner needs without the full API 613 package.

When is AGMA 6011 enough?

AGMA 6011 is enough whenever the application is high-speed but no API standard is contractually required. That covers most test stands, dynamometers, R&D rigs, industrial turbine reduction gears and many centrifugal machine drives outside the oil, gas and chemical sector.

AGMA 6011 is not a light standard. It sets a minimum design life of 40,000 operating hours and uses what Rinaldo describes as the most conservative stress-cycle (life) factor among the AGMA documents, compared with 10,000 hours under AGMA 6013. It also covers lubrication, bearings and testing, not just tooth rating.

What does over-specifying cost?

Over-specifying API 613 on a non-critical unit makes the gearbox larger and more expensive, and at high speed it can make the gear run hotter. The rating gap between standards is large enough to change the design.

The Turbomachinery Magazine analysis compared the same case- and surface-hardened gear set rated under several standards and found about a two-to-one spread from the highest to the lowest rating. API 613 came out most conservative, in part because its ratings are still based on the lowest-grade (grade 1) materials from 1977-era AGMA standards, despite later improvements in metallurgy. The author’s conclusion, given how rare gear failures are, is that even the “least conservative standards are sufficient for most applications.”

The practical consequences of extra conservatism differ by speed:

• Low-speed units: more size, higher price and slightly higher operating losses.
• High-speed units: a wider face to carry the same load means more oil heating across the contact line, and a larger pinion raises pitch-line and sliding velocities. Both raise contact temperature, which increases the risk of varnishing or scuffing.
• Scope: an API 613 specification brings the lube system, controls, instrumentation and auxiliary equipment into the contract scope, with the documentation and inspection that go with them.

In other words, a heavier rating is not automatically a safer gearbox at high speed. The safest specification is the one matched to the real duty and criticality.

How should you choose? A five-step check:

1. Calculate pitch-line velocity and shaft speed. At or above 35 m/s, or above 4,500 rpm, you are in AGMA 6011 territory. Below that, AGMA 6013 is the industrial reference.
2. Check the contract and site specification. If the owner mandates API equipment, that requirement overrides preference.
3. Classify criticality. Continuous service with no installed spare in a petroleum, chemical or gas process points to API 613. Spared or general-purpose service points to API 677.
4. Check for procurement supplements. If JIP33 S-712 or S-713 is invoked, confirm which API edition it aligns with.
5. Write the data sheet around the real duty. State the actual power, speeds, duty cycle, driver type and starts per day, and let the specified standard set the rating method, instead of stacking extra service factor on top of a conservative standard.

Frequently asked questions

Is API 613 “better” than AGMA 6011?

No. It is more conservative and broader in scope for critical petroleum, chemical and gas service. For a high-speed unit outside that context, AGMA 6011 is the appropriate specification, and API 613 mainly adds size, cost and scope.

What is the pitch-line velocity limit for AGMA 6011?

AGMA 6011 applies when at least one stage runs at 35 m/s or more, or above 4,500 rpm, with other stages at 8 m/s or more. Below 35 m/s, AGMA 6013 governs industrial enclosed drives.

Can a test-stand gearbox be built to AGMA 6011 instead of API 613?

Yes. Test stands and dynamometers are high-speed applications, but they are not petroleum, chemical or gas process service, so API 613 does not apply unless the buyer’s own specification calls for it. AGMA 6011 is the usual reference.

What are the current editions of API 613 and API 677?

API 613 is in its 6th edition (July 2021) and API 677 is in its 4th edition (September 2021). Older articles and some procurement supplements still reference the 5th and 3rd editions.

Does API 677 use a less conservative gear rating than API 613?

Not since 1997. API 677 adopted the API 613 rating method in its second edition. The main differences are scope and service classification.

Talk through your specification with an engineer

If you are writing a data sheet for a high-speed gearbox and are not sure which standard your application really needs, Cotta’s engineering team in Janesville, Wisconsin can review the duty, speeds and site requirements with you. Start with the high-speed gearbox quote request form or call (608) 368-5600.

Sources

• ANSI webstore, ANSI/AGMA 6011-J14 (R2019), Specification for High Speed Helical Gear Units: https://webstore.ansi.org/standards/agma/ansiagma6011j14r2019
• ANSI webstore, ANSI/AGMA 6013-B16, Standard for Industrial Enclosed Gear Drives: https://webstore.ansi.org/standards/agma/ansiagma6013b16
• Normservis, API Std 613, 6th ed., July 1, 2021 (scope summary): https://eshop.normservis.sk/norma/apistd-613-ed-6-1.7.2021.html
• Normservis, API Std 677, 4th ed., September 1, 2021 (scope summary): https://eshop.normservis.sk/norma/apistd-677-ed-4-1.9.2021.html
• Normservis, API Std 613 (2021) scope annotation, “continuous service without installed spare equipment”: https://eshop.normservis.sk/norma/apistd-613-1.7.2021.html
• Journal of Petroleum Technology, “JIP33 Publishes Two Gear Units Specs,” Aug. 2, 2020: https://jpt.spe.org/jip33-publishes-two-gear-units-specs
• John M. Rinaldo, “Gearbox Specs: Getting Them Right,” Turbomachinery Magazine, Oct. 7, 2016: https://www.turbomachinerymag.com/view/gearbox-specs-getting-them-right
• John M. Rinaldo, “Gearbox Specs: Getting Them Right” (part 2), Turbomachinery Magazine, Oct. 31, 2016: https://www.turbomachinerymag.com/view/gearbox-specs-getting-them-right-2