Both flat rack (FR) and open top (OT) containers can carry equipment that does not fit readily in a general-purpose container, but the choice is not based on height alone. An open top allows crane loading from above and is often assessed when height is the main constraint. A flat rack has open sides and top, making it a candidate for some overwidth, overlength or side-loaded cargo. Final selection must also account for packed dimensions, unit weight, centre of gravity, load distribution across the base, handling conditions at both ends, and carrier approval of the out-of-gauge and securing arrangement. This guide provides a practical comparison and explains how BLUESea coordinates equipment combinations and site activities in relevant projects.
Identify which dimension creates the loading problem
A general-purpose high cube has a fixed roof, sidewalls and end doors. Cargo must pass through the doors and remain within the internal dimensions and permitted load. An open top removes the rigid roof so a crane can lower cargo from above, while its sidewalls, floor and doors still define important boundaries. A flat rack primarily provides a base and end structures, with open side and top access, so it can be assessed for certain overwidth or overlength units.
Open access does not mean unlimited out-of-gauge freedom. Any overwidth, overheight, overlength or concentrated-weight load depends on the exact container type and condition, terminal handling and carrier acceptance. If a general container, FR or OT cannot provide a sound solution, breakbulk, roll-on/roll-off or another project transport method should be assessed instead of forcing the cargo into unsuitable equipment.
Measure and weigh the cargo in its transport condition
Provide packed length, width, height and gross weight for each unit, not only the bare-machine figures in a sales catalogue. Identify protrusions, skids, wooden cases, pallets and removable accessories. Where available, include photographs, drawings, centre of gravity, lifting points, forklift pockets and areas that must not bear loads. For a production line, prepare an item-by-item list rather than substituting a total weight and volume for the loading details of individual machines.
These details support comparisons of internal dimensions, door or roof access, flat rack deck length and equipment load limits. They also reveal whether weight is concentrated in a small area. Ratings vary by equipment type and individual container, so a generic assumption about how many tonnes a 20-ft unit or how much height a 40-ft unit can accept is not enough. Removing accessories or revising the packing may change the most suitable combination of containers.
- Packed length, width, height and gross weight of every unit
- Centre of gravity, support points, lifting points and removable parts
- Base construction and the area over which weight is distributed
- Origin, destination and the intended shipping window
When should an open top be assessed first?
Start with an OT when cargo length and width can work with the container body, but height or a need for top lifting makes a general container unsuitable. A crane can lower the unit vertically, after which suitable roof covering and securing are arranged for the actual overheight condition. OTs can suit certain large machines, industrial components and heavy units on bases, but the doors, sidewalls, floor and internal clearance still need to match the cargo and handling path.
An open roof does not remove the need to plan rain, dust or movement protection. Tarpaulins and other coverings should be confirmed against cargo protection needs and carrier conditions; covering should not be treated as a guarantee of a fully sealed environment. Gaps between the cargo and sidewalls may require timber supports, cross beams or other suitable bracing, selected for the expected force directions, support strength and site operation.
When should a flat rack be assessed first?
An FR is often worth assessing when the main issues are overwidth or overlength, or when cargo cannot be loaded through general-container doors or into an OT from above. Open sides allow lateral or multi-directional lifting and can accommodate some irregularly shaped equipment. Acceptable projections, use of the end structures and available securing space must be checked against the actual flat rack design and carrier requirements.
The central question is not simply whether the cargo fits on the deck. The base must support it and the cargo must be restrained effectively. A heavy machine may concentrate its weight on a few small support areas, making base support, weight distribution, lashing points and longitudinal and transverse restraint essential. Do not use a weak cargo casing, an unverified equipment bracket or an unconfirmed part of the container as a load-bearing or securing point.
Assess factory, road, terminal and destination handling together
Equipment selection must answer both how the cargo will be loaded and how it will be unloaded. Confirm whether the factory has a crane or forklift of suitable capability, whether the site allows outriggers and vehicles to enter, how lifting gear will connect, and whether the packed unit can be lifted safely. Check comparable conditions at destination; a method that works at the origin terminal may be impossible at the consignee’s site.
Out-of-gauge cargo also requires coordination of pickup vehicles, terminal access, lifting and vessel-side activities. Confirm declaration, loading photographs, site inspections and possible securing adjustments in advance. BLUESea can coordinate flat racks, open tops, breakbulk, roll-on/roll-off services and heavy transport equipment according to cargo dimensions, weight, handling conditions and destination requirements, while connecting lifting, port operations and destination arrangements in one plan.
Design load support and securing for the specific project
A securing plan should start with cargo weight, centre of gravity, base construction, expected transport forces and approved container securing points. Suitable supports, blocking, bracing, wire ropes, chains or other appropriate materials are then selected. Connections, quantities, angles and tension need project-specific review by the relevant competent parties and carrier, with photographs or similar records of the completed work. Appearance alone or one remembered rule cannot establish that a load is secure.
In its Shekou–Damietta injection moulding production-line project, BLUESea used 2×40FR, 2×20FR, 1×40OT and 3×40HQ to accommodate different machines. That project required flat rack units over 20 tonnes to have X-cross lashings at both ends. This was a project-specific operational requirement, not a universal regulation for every carrier, route, container or 20-tonne threshold, and it does not replace load-bearing and securing assessments for any other shipment.
Confirm both the equipment and carrier acceptance before booking
A useful OOG booking application normally needs accurate unit dimensions and weights, a loading drawing, photographs and handling information. The forwarder uses these to request equipment and space. The carrier may ask for further drawings, loading changes or revisions to the securing plan. The plan has an operational basis only after the actual equipment, loading method and carrier conditions are confirmed; a quoted container type does not mean automatic carrier acceptance.
For an assessment by BLUESea, provide the equipment list, drawings, packing photographs, unit weights, centre-of-gravity and lifting information, and handling conditions at the factory and destination. The team can assist with transport feasibility, loading design, out-of-gauge declaration, carrier space applications, and lifting and securing coordination. All special-equipment arrangements remain subject to the specific review, site conditions and carrier approval.
- Do the equipment parameters match the actual container assigned?
- Have loading, projections and weight distribution been reviewed?
- Are responsibilities for handling, support, securing and protection clear?
- Are site records and the process for confirming changes agreed?
FREQUENTLY ASKED
If cargo is simply tall, is an open top always the right choice?
Not necessarily. Check OT internal dimensions, top-loading access, unit weight and base loading first, then determine whether an overheight declaration is needed. Significant overwidth, overlength or lifting constraints may require an FR, breakbulk or roll-on/roll-off assessment.
Must every flat rack load over 20 tonnes use X-cross lashing?
No. X-cross lashings at both ends for units over 20 tonnes were required in the specific BLUESea project described here, not by a universal rule. Each shipment needs a plan based on weight, centre of gravity, base, securing points, applicable standards and carrier review.
Can a flat rack accept unlimited overwidth or overlength?
No. Acceptable projections depend on the actual equipment, loading arrangement, vessel and terminal operations, inland transport conditions and carrier approval. Cargo fitting on the deck does not by itself make the transport arrangement feasible.
What is needed for an FR or OT assessment?
Provide packed dimensions and gross weight per unit, photographs or drawings, base and centre-of-gravity details, lifting points and handling conditions, plus origin and destination. A complete equipment list is important for selecting a container mix for a production line.
