Last updated October 2026
How to Specify an Overhead Crane: The Complete Spec Sheet Explained
Crane vendors quote what you specify — no more, no less. An incomplete spec gets you three quotes for three different cranes, and the cheapest one wins by leaving things out. This guide walks through every line of a proper crane specification so your quotes come back complete and comparable.
1. Rated capacity
The maximum load the crane is designed to lift, including the below-the-hook device (spreader beam, magnet, lifting beam — these count against capacity). Specify the heaviest routine lift, not the once-a-year exception; oversizing for a freak lift wastes money every day for a decade. Common Texas industrial specs: 5, 7.5, 10, 15, 20, and 25 tons.
2. Span
The distance between runway rails — essentially the building bay width minus clearances. Longer spans need heavier girders; every foot matters to the steel weight. Measure the actual runway centerline distance, not the building width.
3. Lift height (hook height)
Distance from the floor (or lowest working level) to the highest hook position. This is where headroom gets decided: single vs double girder, hoist type, and building clear height all interact. Specify the tallest load plus rigging height plus clearance — then verify the building can deliver it.
4. Duty class — the most important line on the spec
CMAA duty classes (A through F) describe how hard the crane works, and they drive structural design, component sizing, and price:
| CMAA class | Service description | Typical use |
|---|---|---|
| Class A — Standby / infrequent | Rare lifts, light loads | Powerhouse turbine rooms, rarely-used maintenance bays |
| Class B — Light service | Light loads, 2–5 lifts/hour | Repair shops, light fabrication |
| Class C — Moderate service | Average loads, 5–10 lifts/hour | General fab shops, warehouses |
| Class D — Heavy service | Heavy loads, 10–20 lifts/hour | Steel service centers, heavy fab |
| Class E — Severe service | Near-capacity loads constantly | Scrap yards, high-volume production |
| Class F — Continuous severe | Constant maximum-capacity duty | Steel mills, dedicated production cranes |
Underspecifying duty class is the classic expensive mistake: a Class B crane doing Class D work will eat brakes, ropes, and contactors, and its structure will fatigue years early. When in doubt, specify one class up — the premium is far cheaper than a premature rebuild. European-spec equipment uses FEM/ISO groups (A1–A8) instead; they map roughly to the same severity scale.
5. Speeds
Bridge travel, trolley travel, and hoist speeds — and whether you need variable speed (VFD) control. VFDs cost more but transform operability: soft starts eliminate load swing, inching becomes precise, and brake and rope life improve dramatically. For any crane doing frequent positioning work, VFDs pay for themselves.
6. Controls
Pendant stations (wired, on the crane) are standard and cheapest. Radio remote controls add a few thousand dollars and are worth it on busy cranes — the operator positions for the best view instead of trailing the load. Cab-operated cranes are for large double girder installations.
7. Electrification
Festoon systems (cables on trolleys in a track) are cheaper upfront and fine indoors. Conductor bar costs more but survives dust, heat, outdoor exposure, and high duty cycles far better. In Houston's humidity or any outdoor installation, conductor bar is the professional choice.
8. Environment
Indoor, outdoor, washdown, hazardous (explosion-proof), high heat, corrosive atmosphere — each drives design decisions from paint systems to electrical classifications. A crane for a Gulf Coast chemical plant and a crane for a DFW warehouse are different machines even at the same capacity.
The spec sheet in one paragraph: capacity (with below-the-hook included), span, required hook height, CMAA duty class, speeds and VFD requirements, control type, electrification type, and environment. Get those eight lines right and every qualified vendor quotes the same crane. Get them wrong and you're comparing guesses. Use our quotes checklist to verify what comes back.
Common specifying mistakes
- Sizing for the heaviest lift ever, not the typical lift. One 20-ton lift a year doesn't justify a 20-ton crane if 95% of lifts are under 5 tons — that's a second hoist or a rental-mobile-crane problem, not a crane-sizing problem.
- Forgetting the hook height. Capacity and span get all the attention; hook height is the spec that kills projects when the tallest lift doesn't clear.
- Specifying duty class by gut feel. Count lifts per hour and average load. The difference between Class C and Class D is a number, not a vibe.
- Leaving the environment blank. Temperature, dust, moisture, hazardous classification — the vendor can't price what you don't disclose, and the change order will be worse than the upfront cost.
- No future-proofing. If the plant might add a heavier product line in five years, pricing the next capacity up now is far cheaper than replacing the crane later.
The one-page spec sheet
Distill the full specification into a one-page summary that travels with the RFQ — vendors read it first and it prevents the most common quoting errors. It should state: crane type and configuration, rated capacity (main and aux), span, lift height, runway length, CMAA duty class or FEM group, speeds for each motion, control type, power supply voltage, environment (indoor/outdoor, temperature, hazards), below-the-hook devices included or excluded, and the standards the crane must meet (CMAA 70/74, ASME B30.2, NEC 610). One page, no ambiguity, attached to every quote request. The vendors who ask good questions about it are the vendors you want.
Frequently asked questions
What is CMAA duty class and why does it matter?
CMAA classes A–F describe how intensively a crane works, from infrequent standby (A) to continuous severe service (F). Duty class drives structural design, component sizing, and price — underspecifying it causes premature wear and is the most common expensive specifying mistake.
What is the difference between CMAA and FEM ratings?
CMAA (A–F) is the North American duty classification; FEM/ISO groups (A1–A8) are the European equivalent. They describe the same concept — load severity and operating intensity — on different scales.
How do I determine the right crane capacity?
Specify your heaviest routine lift including the weight of below-the-hook devices (beams, magnets, grabs). Don't size for a once-a-year exception — that money is wasted every other day of the crane's life.
Are VFD controls worth the extra cost?
For any crane doing frequent positioning, yes. Variable-frequency drives give soft starts, precise inching, reduced load swing, and longer brake and rope life. The operability improvement alone usually justifies the premium.
What hook height do I need?
Tallest load plus rigging height plus safe clearance, measured from the floor to the highest hook position. Verify the building's clear height can deliver it with your chosen crane configuration — single vs double girder makes a 2–4 foot difference.