Materials

The objective was to assess the feasibility of using synthetic-fiber mooring lines for deepwater floating production facilities. The project was a Joint Industry Project (JIP). The research consisted of a laboratory testing program to look at the engineering characteristics of synthetic-fiber mooring lines and the durability and fatigue resistance of their connections. The project conducted a long-term field program to determine environmental effects.

The objective was to determine the susceptibility, of candidate steel and associated weldments on tension leg platforms (TLP) tendons to ripple-load cracking effect on stress-corrosion cracking in salt water. The project used parameters relevant to offshore applications--including those of stress ration, temperature and frequency.

Develop improved guidelines for sizing piping and flow lines that consider the various classes of multi-phase flow, the pertinent fluid chemistry, high-flow rates, and other key variables. An analysis determined the effects of the key variables, such as mixture density, flow velocity, gas-liquid void fraction, sand concentration, fluid temperature, and concentration of corrosive materials. The results of this analysis were used to develop sets of correlations for pipe sizing recommendations. The correlations were tested for validity in large-scale flow-loop tests.

The objective was to develop a methodology to detect, evaluate, and to control local brittle zones (LBZ) in the construction verification of offshore platforms. LBZ's are regions of brittle microstructure within the heat-affected zones of steel weldments that can initiate brittle fracture. They can also cause a fatigue failure to platforms subject to wind and wave loadings. The major objective was to review the test methods that are currently used to detect, assess, and control LBZ's and to make recommendations for new test methods for fracture control.

The objective was to characterize the fatigue properties of several high strength steels (yield stress in the range 60-130 ksi) which are being proposed for deep ocean oil and gas facilities. These materials were to be tested under conditions which are applicable to the service status of offshore structures. The materials were characterized according to the influence of environmental and load variables upon their engineering properties. This was a Joint Industry Project (JIP).

The objective was to assess the major components involved in offshore oil and gas pipeline corrosion. This study identified measurable items which contribute to internal corrosion problems. The project determined if the components identified in the initial stage are capable of being monitored and measured remotely with a minimum of human involvement. As the nation's offshore pipeline system grows older, the net effects of internal corrosion failure will become more acute and the need to remotely monitor internal conditions will increase.

The objective was to assess the possible use of tracer materials in welding consumables for detection of cracking in offshore structures. This trace material would be used only in certain interior beads of multi-pass weldments, thus would only be released into the surroundings if a crack or corrosion damage had progressed a sufficient distance into the material. Periodic scanning of the area adjacent to the defect would detect the presence of the trace material and signal the presence of a crack or corrosion of sufficient magnitude to be a problem.

To examine structural integrity questions arising from the proposed use of high-strength steels in tension leg platforms tension members. Environmental cracking (stress- corrosion cracking and corrosion-fatigue crack growth) will be the major focus of the project. The results will provide engineering criteria relating threshold conditions for the onset of environmental cracking in sea water to design stresses, defect sizes, and cathodic protection parameters for specific classes of high-strength steels.

This is a Joint Industry Project (JIP), sponsored by Minerals Management Service and the Research and Special Programs Administration. The project will study the application of fracture mechanics techniques to problems relating to the maintenance and safety of pipelines and pressure cylinders.

The objective was to study the potentially hazardous effects of Arctic (cold weather) operations on the integrity of steel weldments for Arctic structures. Fracture toughness of steel weldments are being investigated to determine requirements for verifying structural integrity.