Subscribe to our newsletter to receive the latest news and events from TWI:

Subscribe >
Skip to content

Joint corrosion fatigue study

In the light of work indicating that seawater corrosion may be more harmful than expected to cathodically protected tubular joints, SINTEF in Norway and TWI joined forces to produce more data. The two organisations collaborated in a programme to establish fatigue results so that the guidance for tubular joints could be reviewed. Supported by the Department of Energy and a number of industry sponsors, the programme had a budget of over £0.5M.

The tubular geometry investigated consisted of a T joint, with a chord of 914mm diameter and 32mm wall thickness, subjected to in-plane bending. The tests were conducted in synthetic seawater with cathodic protection under constant amplitude loading and simulated broad band wave loading. Tests were also conducted in air for comparison.

The guidance for design of offshore structures in steel included a penalty of a factor of two on fatigue life to allow for seawater corrosion, but no penalty for cathodically protected structures. These provisions arose from fatigue tests on welded plate specimens conducted under the United Kingdom Offshore Steels Research Project (UKOSRP). The results were assumed to be applicable to tubular joints. However, later findings suggested that this comparison was not valid, and that seawater corrosion was more harmful in the case of tubular joints and that cathodic protection was less effective. Data provided by this test programme contributed to a revision of the fatigue design guidance produced by HSE in 1995.

For information about TWI’s capabilities please email contactus@twi.co.uk

}