Left Hand  Lug Right Hand Lug
Integrity Tests

Container Handling Supplement.

Series 1 Freight Container Integrity Tests ISO 1496-3:2019

There are two mandatory strength tests in ISO 1496 Part 4 that apply specifically to container's bottom corner fittings to comply with for them to be issued with a CSC Plate. Together they guarantee integrity of containment of corner fittings, particularly the welding, that secure them to load bearing frames of container freight units. These are simulation Lifting and Constraint tests since it would be prohibitive to conduct dynamic tests in all but the most critical of cases, ie military armament and nuclear materia transport units.

Seperator #1

Test No3 Lifting Test

Lifting from bottom corner fittings ISO1496-3:2019

Lifting test Bottom Corner Lifting Test.
This test simulates the Static plus Live Loads as covered in Lifting Cycle 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 in Table 2  below 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 are recorded.
Series 1
E
A
B
C
D
Nominal Size
45ft
40ft
30ft
20ft
10ft
Angle α
30°
30°
37°
45°
60°

Table 2 Limiting Lifting Angle α

Seperator #2

Test No 4 Constraint 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

Restraint test Restraint Simulation Test
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 2g 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.

Railway Wagon Restraint Test

Wagon restraint test Test freight unit lashing
Lashing lug test Lashing Lug in Corner Fitting
A variant of the lug used for lashing freight units to wagons, not fitted with twislocks, was subjected to an actual restraint test to ascertain is viability for this use.The lugs were reconfigured such that they where capable of sustaining maximum load when horizontal. The construction of the lug allows for the retaining head to be fixed at any angle within the shoe body and in this case the retaining head and body axes were aligned requiring the lugs to be inserted when vertical. Once coupled they could not fall free whilst lashing chains were tensioned.