Integrity Tests

Test No3 Lifting Test

Lifting from bottom corner fittings ISO1496-3:2019

This test simulates the Static plus Live Loads as covered in by doubling the MGW capacity. A uniformly distributed internal payload P having the value of ( 2R - T) is applied over the floor of container to give twice the rating of 2R and is lifted by slings attached to a central beam at the limiting angles shown below in Table 2,  and suspending it to induce a force of 2Rg. This lifting mode also tests the frame strength induced by the resolved horizontal compressive forces that result from accutely angled slings. The unit remains suspended for 5 minutes and when lowered, any permanent deformations of the frame being recorded.

Test No 4 Restraint Test

When mounted on a transport unit, and in motion, twistlocks transfer forces to the unit when accelerating and braking via the corner fittings, these forces in turn, are reacted by the bottom side rails of the container frame via direct horizontal forces. These horizontal shear forces are influenced by the rigidity of the platform on which the unit is mounted. (Another set of vertical forces are also induced by the inertia force acting at the C of G above the corner fittings resulting with the familiar effect of the forward end tipping down when braking and rearing up during acceleration. This inertia or body force is product of mass x acceleration acting at the C of G of freight unit hence the need to keep C of G as low as possible.)

Restraint Simulation Test ISO1496-3:2019

This test subjects the container to horizontal corner forces only and neglects both the stiffness of the support platform and inertia effects. The unit is supported on all four corner fittings alone, a pair being fixed at one end, whilst the opposite end pair are attached to sliding supports. Horizontal forces are applied to these corner fittings, usually via hydraulic cylinders, to simulate dynamic forces induced by acceleration and braking. These forces simulate ± 2g acceleration and are evaluated from the product of MGW x 2 only or Rx2g. The loading is uniformly distributed having a total value of R - T.
These simulated dynamic forces are replicated by applying half the total horizontal force simultaneously to each corner fitting attached to sliding supports, first pulling and then pushing, inducing tension and compression respectively in the bottom side rail that, in addition, is under bending due to distributed internal loading. The horizontal direct tensile forces (applied in opposite direction to that shown here) are more critical than the compressive forces induced by pushing. Such tensile forces occur when lifting slings are acting in outboard directions, opposite to the more usual vertical and inboard angled arrangements.