Use this for RFQ clarity
Share the estimated duty class and the assumptions behind it. Do not ask vendors to quote only "5 ton crane" without usage details.
EOT Crane Duty Class Selector
Estimate a preliminary duty class and turn your use pattern into supplier-ready RFQ wording.
Read the EOT Crane Duty Class GuideQuick answer
Duty class tells the supplier how hard the crane will work, not just how much it can lift. A 10 ton M3 maintenance crane and a 10 ton M7 production crane are not equivalent. Use this selector to describe load spectrum, operating hours and application, then ask vendors to confirm the final duty basis.
Required Duty Class
--
FEM: --
Application Type
-
Operating Class
-
Buyer Meaning
-
Why Duty Class Matters
The Duty Class (FEM or ISO) dictates the physical robustness of your EOT crane. It is arguably the most important specification on your RFQ. A crane rated for 10 tons at M3 duty is physically smaller and lighter than a crane rated for 10 tons at M8 duty.
- Under-specifying (e.g., buying M3 for a foundry): Leads to rapid gear wear, motor burnout, and structural fatigue cracks within months.
- Over-specifying (e.g., buying M8 for a maintenance shop): Wastes capital expenditure on excessively heavy and expensive equipment that will never be fully utilized.
Ask vendors to confirm
Request selected crane duty, hoist duty, motor duty, brake basis and design assumptions in the technical offer.
Escalate high duty
For M7, M8 or process cranes, involve qualified engineering review before purchase-order release.
| Typical result | Buyer interpretation | RFQ caution |
|---|---|---|
| M3 / M4 | Light maintenance, low running time or occasional use. | Do not overpay for heavy duty if usage is genuinely light. |
| M5 / M6 | Regular workshop or production support use. | Make vendors state component duty, brake sizing and expected operating assumptions. |
| M7 / M8 | High-use, heavy load spectrum or process-critical operation. | A cheap low-duty quote can fail early. Ask for stronger design evidence and service plan. |
| M8+ | Extreme or continuous process duty. | Use this as an escalation flag, not a final selection. Require detailed engineering review. |
Purpose
Use this duty class selector before sending an RFQ so suppliers understand the operating severity, not just the crane capacity. It helps procurement teams avoid non-comparable quotes where one vendor prices a light-duty crane and another prices a production-duty crane.
Inputs Explained
- Application: gives context such as maintenance, workshop, production, foundry or process use.
- Load spectrum: describes how often the crane lifts light, medium, heavy or near-rated loads.
- Operating hours: estimates active crane use, not only shift length.
- Operating days: supports design-life and RFQ discussions.
Formula Basis
This tool uses a simplified duty-selection matrix that maps load spectrum and daily active operating time to a preliminary ISO/FEM-style duty class. It is meant to prompt the right vendor questions, not to replace a full classification calculation.
Assumptions
The result assumes the entered operating time and load spectrum describe normal crane use. Shock loading, grab/magnet duty, high ambient temperature, corrosive environment, high starts per hour or process-critical duty can push the final design requirement higher.
Worked Example
A 10 ton crane used for regular production support, lifting medium to heavy loads for about 4 hours per day, may fall around M5 or M6 as a preliminary RFQ assumption. The supplier should still confirm mechanism duty, starts per hour, motor thermal duty and brake selection.
Results Interpretation
Treat M3/M4 as light or occasional use, M5/M6 as regular production or workshop use, and M7/M8 as severe or process duty. If the result is high, do not compare it against a low-duty quote without asking for the full design basis.
Limitations
This is a preliminary buyer-side selector. Final duty classification should consider applicable standards, load spectrum factor, operating cycles, starts per hour, mechanism group, design life, environment, control method and manufacturer design rules.
Related Standards
Crane duty classification is commonly discussed through ISO mechanism groups, FEM classes and local crane design practices. Use this page as an RFQ conversation starter and ask suppliers to state the exact standard and classification basis used in their offer.
FAQ
What is EOT crane duty class?
Duty class describes how frequently and how heavily a crane is expected to operate. It considers load spectrum, operating time, starts, application and design life. It is different from rated capacity.
Is M5 duty enough for a production crane?
M5 may be suitable for regular workshop or moderate production use, but heavier load spectrum, long operating hours, process-critical operation or frequent full-load lifting may require M6, M7 or M8.
Can this selector replace engineering design?
No. This selector provides preliminary RFQ guidance. Final crane and mechanism duty selection must be confirmed by the crane supplier or qualified engineer using applicable standards and project data.
Next action
Put this duty assumption into your buying workflow
Use the duty result with capacity, span, lift, speeds, controls, environment and component makes before sending quotations to suppliers.