An overhead bridge crane (OBC) is an EOT (electric overhead traveling) crane that runs on two parallel runways, with a hoist and trolley traversing the bridge girder, and is governed in the U.S. by ASME/ANSI B30.2 and OSHA 1910.179 [S1][S4].
For demolition work, the bridge crane typically handles 5 to 50 ton loads and is paired with a demolition hammer or grapple for concrete, steel, and masonry break-out, with service classification driven by load spectrum and duty cycle rather than peak tonnage [S1][S2].
Service Classification: Why CMAA Class D or E Is the Floor for Demolition
CMAA 70/74/78/79 define six service classes (A through F) for overhead cranes, with Class D corresponding to heavy-duty production and Class E to severe-duty continuous operation typical of scrap yards and demolition [S1].
Demolition crews should treat CMAA Class D as the minimum acceptable floor for any bridge crane expected to handle a demolition hammer or wrecking ball, and step to Class E when the crane will see more than 5 cycles per hour under 50 to 100 percent of rated load [S1].
A Class F (standby / infrequent) bridge crane is the wrong tool for demolition because its hoist and bridge structural members are not designed for the dynamic, irregular load patterns of wrecking attachments; matching the class to the work cycle is what keeps the crane inside its fatigue envelope [S1].
Structural and Runway Requirements Under Repeated Shock Loading
Wrecking-ball and demolition-hammer work introduces shock factors of 1.0 to 1.5 times static load on the hoist, trolley, and bridge girders, which is why CMAA Class D and E cranes carry higher structural safety factors than Class A or B units [S1].
Runway beams supporting a demolition-rated bridge should be checked for lateral loads from swinging loads, with end trucks specified for the full rated capacity and bumpers rated for 50 to 100 percent of crane travel speed at full load [S1].
Engineers specifying a demolition bridge crane should also confirm runway rail clamping, weld quality, and alignment against ASME/ANSI B30.2 runway tolerances, because the dynamic loads from a demolition hammer attachment amplify any pre-existing rail misalignment.
Hoist, Trolley, and Bridge Drive Choices
For demolition service, wire-rope hoists with two-speed or VFD (variable frequency drive) control are preferred over single-speed chain hoists, because the operator needs controlled inching to position a swinging load or set a wrecking ball [S1][S2].
Trolley and bridge drives should be specified with VFDs on all motions to limit inrush current and reduce wheel slip on the runway, with motor enclosures rated for the dust and debris environment typical of indoor demolition (IP54 minimum) [S1].
For structural steel demolition where the crane is also used to lift cut members out of the building, a crawler crane is sometimes deployed on the ground floor, but a bridge crane remains the right tool where the work is inside a bay and the runway already exists [S1].
Comparing Bridge Crane vs. Gantry Crane vs. Mobile Crane for Demolition
Across the main decision criteria, an overhead bridge crane scores high on lifting height clearance, repeatability, and integration with existing runways, but lower on mobility than a mobile or crawler unit; a gantry crane splits the difference, giving ground-level mobility without runway investment. [S1]
Where runway rails are already installed, a bridge crane is the lowest-cost-per-lift option for high-cycle demolition work; where the site is open ground with no fixed runways, a gantry crane on rails or rubber tires is more practical, and a mobile hydraulic crane is the correct choice only for short-duration lifts or reach-in work outside the bridge's coverage [S1].
Key criteria: bridge crane = fixed bay, high cycle, low cost per lift; gantry crane = outdoor or temporary bay, medium cycle; mobile/crawler crane = one-off lifts, reach work, no runway dependency [S1][S2].
Safety, Standards, and Inspection Cadence
OSHA 1910.179 incorporates ASME/ANSI B30.2 by reference, and that standard defines daily visual checks, periodic inspections at 1 to 12 month intervals depending on service, and load testing after major structural repairs [S1].
For demolition service, the daily pre-shift check should include hoist brake setting, wire-rope condition at dead-end terminations, hook safety latch operation, and trolley rail wear, because these items see the highest wear rate under shock loading from a demolition hammer or ball [S1].
Operators must hold qualification per OSHA 1910.179 and the employer's certification program, and the crane must carry a visible capacity plate; for demolition work, derating the nameplate capacity by 10 to 25 percent is a common engineering practice to extend component life under repeated shock [S1].
Who This Crane Is For, and Who Should Specify Something Else
An overhead bridge crane is the right specification for demolition contractors working inside an existing industrial bay, steel-mill scarfing, or refinery unit shut-down where the runway is already engineered for crane service and the cycle rate is high [S1][S2].
It is the wrong tool for first-pass site clearance on open ground, for reach work over existing structures, or for projects where the demolition is short and the runway investment cannot be amortized; in those cases a gantry crane on portable rails or a mobile hydraulic crane is the more honest specification.
For load monitoring during demolition lifts, a crane scale hung between the hook and the wrecking attachment is the standard way to verify that shock loads stay inside the crane's rated capacity, and is required by most site safety plans for Class D and E service [S1].
Sourcing, Lead Time, and What to Ask the Vendor
Lead time for a custom-engineered Class D or E bridge crane typically runs 16 to 26 weeks from purchase order to commissioning, with on-site installation adding 2 to 6 weeks depending on runway condition and electrical scope [S2][S3].
Buyers should request CMAA service-class letter, ASME/ANSI B30.2 compliance statement, OSHA 1910.179 reference, hoist duty rating in FEM/ISO groups, and full disclosure of wire-rope, sheave, and brake specifications before issuing a PO [S1].
For buyers also weighing an overhead conveyor system for moving demolition debris out of the bay, a bucket elevator is a complementary material-handling option for vertical debris lift, but it is not a substitute for the bridge crane on the heavy-lift side.
Trackable signals for the next buying window: CMAA Specification 70/74/78/79 revision notes, OSHA 1910.179 interpretation letters referencing demolition attachments, and any new FEM 1.001 / ISO 4301 service-class harmonization language appearing in OEM submittals.