The U.S. Army Corps of Engineers’ Safety and Health Requirements in Construction is the military’s safety bible for building its infrastructure, and much of it is directly applicable to marine construction.
This article is taken from its section on the supplemental requirements for “floating cranes/derricks, land cranes/derricks on barges, pontoons, vessels or other means of flotation and auxiliary shipboard mounted cranes.”
Load Rating
The load rating of a floating crane/derrick shall be the maximum working loads at various radii as determined by the manufacturer or qualified person considering list and trim for each installation. The load rating shall specifically reflect the: design standard; machine trim; machine list; and dynamic/ environmental loadings anticipated for the operational envelope of the floating crane or auxiliary shipboard crane.
A Naval Architectural Analysis shall be performed to determine these parameters that shall be used in generating the load rating.
- The load rating is dependent upon the structural competence of the crane, rope strength, hoist capacity, structural attachment to the floating platform, and stability and freeboard of the floating platform.
- When deck loads are to be carried while lifting, the situation shall be analyzed for modified ratings.
- When mounted on barges or pontoons, the rated loads and radii of land cranes shall be modified as recommended by the manufacturer or qualified person. The modification shall be evaluated by the qualified person specific to the flotation device/ platform being used.
- Load charts shall be posted in the cab or at the operator’s station (if no cab). All other procedures applicable to the operation of the equipment (instructions and operators manual, recommended operating speeds, etc.) shall be readily available on board.
Load charts shall, at a minimum, identify the following:
- Naval Architect Notes:
- draft limits (with deck cargo considered);
- vessel motion limits; • vessel and crane list/trim limits, and
- vessel condition (e.g., dry bilges, watertight integrity, etc.).
- crane manufacturer notes, or reference to them.
- Safe Working Load Chart with:
- mode of operation;
- environmental limits;
- capacity (net or gross);
- load, boom elevation, radius (with list/trim considered), and
- crane configuration, to include boom length, amount of counterweight, parts of wire, and block size.
Floating cranes/derricks
All floating cranes/ derricks intended for permanent attachment to a barge, pontoon or other means of flotation shall be designed in accordance with the requirements of 46 CFR 173.005 through 173.025.
Load Charts
The manufacturer load charts applicable to operations on water shall not be exceeded. When using these charts, the employer shall comply with all parameters and limitations (dynamic, environmental, etc.) applicable to the use of these charts. The load charts shall take into consideration a minimum wind speed of 40 mph (18 m/s).
Maximum Operating List or Trim
Unless the crane manufacturer recommends a lesser value, maximum operating list or trim shall comply with requirements below:
- Cranes designed for marine use (barge or pontoon mounting) by permanent attachment, with a rated capacity of up to 25 tons (22,680 kg) shall have a maximum allowable list or trim of 5º.
- Cranes designed for marine use (barge or pontoon mounting) by permanent attachment, with a rated capacity of greater than 25 tons (22,680 kg) shall have a maximum allowable list or trim of 7º, although 5º is recommended.
- Derricks, designed for marine use (barge or pontoon mounting) by permanent attachment, of any capacity shall have a maximum allowable list or trim of 10º.
Stability
The equipment shall be made stable with the following maximum allowable freeboard requirements:
- operated at rated capacity, 60 mph (100 kph) wind, 2 ft (0.6 m) minimum freeboard;
- operated at rated capacity plus 25%, 60 mph (100 kph) wind, 1 ft (0.3 m) minimum freeboard;
- operated at high boom, no load, 60 mph (100 kph) wind, 2 ft (0.6 m) minimum freeboard; and
- for backward stability of the boom—high boom, no load, full back list (least stable condition)— and a 90 mph (145.8 kph) wind.
If the equipment is employer-made, it shall not be used unless the employer has documents demonstrating that the load charts and applicable parameters for use meet the requirements of paragraphs 16.L.03.a, b and c. Such documents shall be signed by a marine engineer or a registered professional engineer who is a qualified person with respect to the design of this type of equipment (including the means of flotation).
Land cranes/derricks mounted on barges, pontoons or other means of flotation.
The rated capacity of the equipment (load charts) applicable for use on land shall be reduced by the equipment manufacturer, or a qualified person who has expertise with respect to both land crane/derrick capacity and the stability of vessels/flotation devices.
The rated capacity of the equipment for use on land shall be reduced to:
- Account for increased loading from list, trim, wave action and wind;
- Be applicable to a specified location(s) on the specific barge, pontoons, vessel or other means of flotation that will be used, under the expected environmental conditions;
- Insure that the maximum allowable list and trim for the land crane/derrick shall not exceed the amount specified by the crane/derrick manufacturer or if not specified, the amount specified by the qualified person;
- Maximum allowable list and trim for the barge, pontoon, or other means of flotation shall not exceed the amount necessary to ensure that:
- all deck surfaces of the barge, pontoon or flotation device shall be above the water;
- the entire bottom area of the barge, pontoon or flotation device shall be submerged; and
- the maximum allowable list or trim shall not exceed the least of the following: 5º, the maximum specified by the crane/derrick manufacturer or if not specified, the amount specified by the qualified person.
Physical attachment
Derricks shall be secured to the deck to transmit the loading to the barge or pontoon. Cranes shall be blocked or secured to prevent shifting.
The crane shall be allowed to travel on the barge for repositioning only. If traveling is required while lifting the load, this lift shall be deemed a critical lift and a critical lift plan is required. It must include a Naval Architectural Analysis to determine these parameters. A marine engineer or registered professional engineer familiar with floating crane design shall perform this analysis. In addition, the manufacturer’s recommendations shall be followed.
When loads approach the maximum rating of the crane or derrick, the person responsible for the job shall ascertain that the weight of the load has been determined within +/- 10% before it is lifted.
Safety devices and Operational Aids
In addition to those previously mentioned, the following are required:
- pontoon, barge, vessel or flotation device list and trim device: shall be located in the cab or at the operator’s station (if there is no cab) as a means for the operator to visually determine the list and trim;
- wind speed and direction indicator: within clear view of the operator’s station;
- anti two-block device (only when hoisting personnel or hoisting over an occupied cofferdam or shaft); and
- principal walking surfaces shall be of a skidresistant type. In addition to inspection of the crane/derrick, inspection of the barge, pontoons, vessel or other means of flotation used to support a land crane/ derrick by a competent person is required:
- On each shift, the means used to secure/attach the equipment to the vessel/flotation device shall be inspected for proper condition, to include wear, corrosion, loose or missing fasteners, defective welds and (where applicable) insufficient tension.
- The vessel’s means of flotation shall be inspected on a monthly basis for the following:
- taking on water;
- deckload for proper securing;
- chain lockers, storage, fuel compartments and battening of hatches for serviceability as a water-tight appliance; and
- firefighting and lifesaving equipment in place and functional.
If any deficiency is identified, an immediate determination shall be made by a qualified person as to whether the deficiency constitutes a hazard. If so, the vessel/flotation device shall be removed from service until it has been corrected.
Operations
Operators shall monitor the wire lead from the boom tip carefully to ensure that limits on off-lead and side-lead identified in the load chart are not exceeded.
- Operators shall monitor environmental criteria for compliance with the criteria set forth in the load chart.
- Operators should be aware that safety devices such as LLD(s) and LMI(s) do not offer protection against loads generated by relative motions between a floating crane and a fixed object to be lifted.
- Whenever practical, crane use during buoy tending shall be limited to lifting the freely suspended buoy clear of the water onto the vessel.
- Bilges shall be kept as dry as possible to eliminate the adverse effect of free surface (sloshing liquid).
- All lifts must be planned to avoid procedures that could result in configurations where the operator cannot maintain safe control of the lift. (A plan, in this case, might be a quick discussion with the deck crew, and a verification of the proposed operation.) Lifts shall reflect floating operational parameters such as: anticipated values for wire leads, unknown load for extractions, and upper limits on crane force.
Reprinted from Marine Construction Magazine, Issue II, 2024
