In cold chain logistics, temperature control is the focus — while the structural load-bearing capacity of the container itself is often overlooked. A reefer container weighs 2.2 to 2.4 tons empty, and its gross weight can reach 30 tons fully loaded. If stacking heights exceed the limit, the pressure borne by the corner castings of the bottom tier far exceeds design values, leading to underframe deformation, door-lock failure, and crushing or leakage of refrigeration piping.

The International Maritime Organization and individual shipping lines have set clear rules on stacking heights for reefer containers. On-vessel stacking for standard 20ft reefer containers is generally capped at two tiers; 40ft containers at three tiers. Stacking operations at terminal yards are more conservative still, with ground-level stacking typically limited to two tiers. These numbers are not arbitrary — they are derived from corner-casting load-bearing capacity, underframe structural strength, and long-term fatigue testing data. Exceeding the limits causes stress concentration at the corner castings, accelerating metal fatigue, and the underframe crossmembers may suffer irreversible deformation.

Stacking capacity varies significantly across different reefer container types. Open-top containers lack a roof structure, so their stacking height is one tier less than that of standard closed containers. Side-door containers have weaker structural integrity at the door frame area, so when stacking, the door frames of adjacent containers must not be aligned, otherwise loading becomes uneven. Frame-type reefer containers have no side walls or roof and rely primarily on the corner castings and underframe to carry the load, making their limits even more stringent. Operators in the field must make judgments based on container markings and actual structural conditions, rather than applying a single rule across the board.

Safe operation also extends to other details. Before stacking, bottom corner castings should be inspected for deformation, and weld seams checked for cracks. Corner castings of upper and lower tiers must align, with deviation kept within 5 mm. Once stacking is complete, twist locks or lashing straps should be used to secure the load, preventing container slippage when the vessel rolls. Operating the refrigeration unit under stacked conditions for extended periods is not recommended, as compressor oil return may be compromised by container tilt. Each of these details seems minor on its own; combined, they form the safety floor.

The core of reefer container stacking safety lies in respecting the structural design of the container. Tier limits set the floor; operating standards provide the safeguard. Logistics enterprises need to embed these requirements into every loading and unloading operation, leaving no room for complacency — one fewer tier in the stack means one more measure of safety.

CIMC Qingdao Refrigeration Industrial Base, established in 1999, is dedicated to the design and manufacture of ISO standard reefer containers as well as the production and customization of a wide range of refrigerated and insulated specialty products, serving customers across major logistics systems throughout North America, Europe, Asia, Australia, and beyond. The base's products cover application scenarios across the "sea, land, and air" supply chain systems, providing full-process equipment manufacturing solutions for cold chain equipment — from pre-cooling at production origins and manufacturing to midstream logistics transportation and last-mile warehousing. For more information about reefer containers, we warmly welcome your inquiry.

Address: No. 66-68 Xiangjiang Road, Jiaozhou City, Qingdao, Shandong Province

Telephone: +86-532-86687388 / +86-532-86687636 (Aviation Container)

E-mail: customer_service@cimc.com / yunfeng.bi@cimc.com (Aviation Container)

Website: www.qdcimc.com