Objective
This project aims to demonstrate the effectiveness and validate the reliability of optimised circular shaped hollow charges for use in the cutting of large steel jacket legs.
The promoter intends to take the present shaped charge technology, whose capability in producing a fine cut around a small diameter and wall thickness tubular in shallow water is well proven, a substantial step further towards addressing the hitherto untackled problem of producing a wide cut around a large diameter thick walled jacket leg made from 50D steel at water depths below 75m. The new design has to work within the environmental requirement for an engineered tool of low explosive weight, a high degree of safety and reliability and with least collateral damage and environmental impact.
The project endeavors to have available an integrated circular shaped charge cutting system whose capability in cutting thick, large diameter jacket legs in deep water which is validated and proven for commercial production and whose validation test data will be made available for future abandonment activities.
The series two tests on 120° sections of BS 4360 50D steel 70 mm thick, radius 1500 mm, were all successful. The charges proved their capability to cut through both the steel and through a water gap of 12 mm, thus demonstrating their robustness to uncertain conditions in underwater application.
The third series of tests on full tubular sections, 360° by 3 meters long, BS 4360 50D steel 70 mm thick radius 3000 mm diameter were all successful. The test have been repeated, varying both the explosive used and the water gap. The charge has proven that it has good reliability, robustness to conditions and flexibility in use of materials. The procedures for manufacture and installation have been verified.
The explosive cutting tool is essentially a linear hollow shaped bent into a circular arc so that it can encircle the jacket leg to be cut. Linear hollow shaped charges use the principle of generating a cutting jet by explosively accelerating thin copper V-shaped liners. The metal jet travels unobstructed and impinges on the target. The cutting action is in the form of eroding and cratering of the target material. The front part of the jet is responsible for penetrating the near surface of the target whilst the tail of the jet perforates the remainder of the thickness. There have been enormous advances in the defense sector in the area of shaped charge cutting technology. The main aim in that discipline is to produce the deepest penetration in armour plating by a circular cross section jet generated by a conical shaped charge. However, far fewer advances have been made in linear shaped charge cutting. There are numerous designs for cutting plates and circular tubes of thin walledsection. Some of these designs have been used offshore in the cutting of small diameter legs, guide posts and mooring chains. Due to the need to expel the water from the path of the jet various designs of robust casings are available to make these charges work under water. Occassionally, inflatable diagraphms are used with air pumps to counter the hydrostatic head.
These charges were also used in the form of a toroidal construction placed inside or enveloping a tubular target. In order to make it conform closely to the tubular inside (or outside) surface it is used in two or three segments. The jets will have to cut through the casings before actually cutting the target.
To our knowledge, so far, none of these charges have been used in the cutting of a large diameter thick walled jacket leg (upwards of 2.5 m diameter, 65 mm wall) made of 50 D steel. Furthermore, most shaped charge designs produce narrow width cut. The requirement when cutting a steel jacket is for a wide cut to ensure abundant clearance between the two cut halves, which the present tool will achieve in water depths below 75 meters.
Programme(s)
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
W5 1XL London
United Kingdom