Flare tips are essential for safety. Maintenance is difficult and costly. Flare tips are subjected to high combustion temperatures, thermal cycling, oxidation and marine corrosion. Following a number of flare tip failures an in depth study by Imperial College was carried out into the failure of a flare tip from a UK platform, looking for service life improvement. Materials selection and design solutions were considered. The study considered alternative materials and concluded that materials selection was the smaller part of the answer; design changes can double service life. This study used failure investigation, high temperature experimental and thermo-mechanical modelling analysis.
The modelling process simulated two common flaring conditions and correctly predicted the observed failure of initiation and crack propagation from holes used to bolt on flame stabilizing plates to the top of the flare. The calculated thermal stress and strains enabled the low cycle fatigue life and minimum creep life to be predicted. It was concluded that service life could be improved by replacing Incoloy alloy 800HT (UNS N08800) with Inconel alloy 625 (UNS N06625), an alloy with attractive mechanical properties and improved high temperature corrosion resistance. Repositioning or eliminating bolt holes can double service life.