CMAA 70/74 Crane Consultant
CMAA 70 and CMAA 74 are the design specifications the vast majority of North American overhead cranes are built to — and the single most common cause of premature crane failure and re-work is a mismatch between the CMAA service class the crane was purchased under and the duty cycle the plant actually runs. Crane Advisory Group specializes in getting that class right, up front, before the purchase order is issued.
When you need this
Signals it's time to engage CAG.
- You are writing a new crane specification and need to lock in the correct CMAA service class (A through F)
- Bidders have proposed different CMAA classes for the same duty and you need an independent tiebreaker
- An existing crane is failing prematurely and you suspect it was purchased under-classified
- Your process is changing (throughput increase, new product line) and you need a duty-cycle re-assessment
- An EPCM is specifying a Class C crane for a facility that will clearly run Class D or E
What we deliver
Concrete outputs, not just advice.
- —Duty-cycle assessment translating actual lift frequency and load spectrum into a defensible CMAA class
- —CMAA 70 / 74 aligned specification package suitable for competitive bid
- —Structural design review of vendor proposals against CMAA 70 (top-running, double-girder) or CMAA 74 (top-running, single-girder)
- —Written class-recommendation memo for capital approval and insurer files
- —Cross-referenced ASME B30 inspection and PM cadence tied to the CMAA class
CMAA service class is the single design decision that governs the entire life of the crane — bridge and girder sizing, drive selection, brake duty, hoist class per HMI, PM interval per ASME B30, and ultimately the replacement horizon. Under-classify by one letter and the plant absorbs the cost as premature wear, unplanned downtime, and an early replacement. Over-classify by one letter and the plant absorbs the cost as capex it did not need. Our role is to make that decision on the owner's evidence — logged lift counts, load histograms, ambient conditions — rather than on the vendor's marketing.
CMAA 70 covers top-running double-girder electric overhead traveling cranes; CMAA 74 covers top-running single-girder. Both specifications use the same A-through-F service class framework, but their structural design rules and the load capacity ranges they realistically address differ. A CAG specification package always names the governing document (70 or 74), the service class, and the design criteria explicitly, so there is no ambiguity for bidders and no room for a vendor to substitute a lower design standard mid-project.
In practice, the CMAA class also drives every downstream document — the ASME B30 inspection frequency, the CMMS PM cadence, the operator training profile, and the spare-parts stocking plan. Getting the class right at specification time cascades through every operating cost for the next 25 to 40 years of the asset's life.
Standards referencedCMAA 70, CMAA 74, ASME B30.2, ASME B30.17, HMI 100 hoist duty class, AISE Technical Report 6 (mill duty).
Frequently Asked
CMAA 70/74 Crane Consultant, answered.
- What is a CMAA service class and why does it matter?
- CMAA service class (A, B, C, D, E, or F) describes the duty cycle a crane is designed for — a combination of load spectrum and cycles per hour. It drives the structural, mechanical and electrical sizing of every component and is the single most important number on a crane specification. Wrong class = premature failure or wasted capex.
- What is the difference between CMAA 70 and CMAA 74?
- CMAA 70 governs top-running, double-girder electric overhead traveling cranes; CMAA 74 governs top-running, single-girder. Both use the same A–F service class system but apply different structural design formulas appropriate to their geometry. Wall-mounted, underhung, gantry and jib cranes are covered by their own CMAA volumes (71, 74, and MMA specifications).
- How do I know which CMAA class applies to my process?
- It requires a duty-cycle assessment: lifts per hour, load as a percentage of capacity, environment, and expected life. A steel-mill hot-metal crane is Class F; a maintenance-shop crane is often Class A or B; most manufacturing production cranes fall in C, D or E. We build the assessment from your operations data — not from the vendor's default.
- Can you review a vendor's structural calculations against CMAA 70?
- Yes. Structural design review — girder sizing, end-truck wheel loads, deflection limits, fatigue design against the CMAA fatigue curves — is a core CAG deliverable, particularly on large capital projects and modernizations that keep the runway but replace the crane.
- Do CMAA classes translate to hoist duty (HMI/FEM)?
- Yes, and getting the translation right is essential. A CMAA Class D crane needs a hoist duty class higher than the default many vendors ship — typically HMI H4 or FEM 2m minimum — and the spec must name it. Our specification packages explicitly cross-reference CMAA class to HMI hoist duty and, where relevant, FEM class.
- Is CMAA a code or a specification?
- CMAA 70 and 74 are consensus design specifications published by the Crane Manufacturers Association of America (a bureau of MHI). They are not regulations, but they are the design basis referenced by every mainstream US overhead crane manufacturer — which makes them the de-facto standard for procurement, bid evaluation and litigation.
Where to go next
The logical next step.
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Write the correct service class into the specification before bidding. Crane Specifications & RFQ.
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Check that quoted cranes actually meet the class you asked for. Independent Bid Review.
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Under-classified crane? Compare the realistic options. Repair, Modernize or Replace.
Ready to talk about your crane decision?
Independent, owner-side review. No obligation, no sales pitch.
Before you approve the quote, make sure it is solving the right problem.
CAG independently reviews major crane proposals, repairs, modernization projects and replacement recommendations so owners can make informed decisions before committing capital.