6.1.1 Discussion D4 -lower breaking point:

What did the breaking point of D4 look like? The middle part of bracing D4 was picked up from the seabed and brought ashore from the Ekofisk field approx one month later. The assembly of bracings D3, D4 and DE are shown in section 2.0 Assembly of bracings. Normally one should aspect the breaking points of D4 to fit with the breaking point on the D-leg on the one end and on the platform on the other end as on DE and D3. The reason for material missing in the upper breaking point is explained by the explosion in this area.
2.0 Assembly of bracings
How come there also is indicated material missing in the lower breaking point towards the D-leg? The possibility of focusing weak shock waves making the bracing explode in both ends was outruled by calculations performed by experts at Caltech, Los Angeles, in 1986. The implosion in the lower part caused by the explosion in the upper part will only make the bracing burst, be sucked in, at a point were the combined under presure inside the bracing and the waterpressure outside the bracing is larger than the carrying capacity of the steel bracing. In this case it happened at a distance of 7.5.meters from the D-leg, see fig 6.1.1. Thus the shape of both fractures at the D4 bracing lower breaking point should look the same unless one or both have been manipulated. Photo 6.1.1 showns the D4 lower breaking point on the middle part of the bracing picked up from the seabed approximately one month later.
Photo 6.1.1; D4 lower breaking point.
Characteristic for this picture is the sucked in part on left side of the end fracture. Further the smoothly rounded edge shaped by water being sucked into the bracing in order to help equilize inside and outside pressure. Air is at the same time flowing back into the bracing through the upper breaking point. (This is further explained in section dealing with material testing of D4 upper breaking point.)
Section 2.1 Material testing of D4 upper breaking point
The D4 cut-off peace from the D-leg as presented in the Statoil and Commissions report has a different shape, see photo 6.1.2 and fig 6.1.2.
Photo 6.1.2 D4 lower breaking point at D-leg side after cut off.

Fig. 6.1.2; D4 lower breaking point at the D-leg.

Note the sharp corners. What forces in the North Sea is capable of making such deformations? On the inside of the lower corner is a crack in the wall. The "oval" shape some distance from the opening corresponds with what would be expected by implosion. Is the opening fracture manipulated ? see fig 6.1.3.

Fig 6.1.3; D4 lower breaking point at the D-leg, manipulated - are the sucked in opening straighted out ?

The doted line on fig 6.1.3 indicates the shape of the opening corresponding to the breaking point on D4 middle part as shown on photo 6.1.1. Rotate fig 6.1.3 with the doted line 90 degrees to get correspondance. The sharp corners seems to be the result of some tool pressing against the inner wall of the bracing straightenining out the lower corner on the figure and making the steel crack on the inside.