RA330® Flare Tips
Leading flare tip manufacturer Kaldair, recently turned to RA330 following an increasing number of failures among larger versions of its Indair flare design. The Indair flare, designed with a tulip-shaped body with an alloy cone joined by circumferential butt weld, had been operating reliably for over a decade using alloy 800H, until a number of tips were found to be failing around the weld joint.
It was concluded that the problem was a mixture of strain age cracking and thermal fatigue, which linked to the differences between alloy 800H and the dual certified 800/800HT alloy which succeeded it in the 1980s along with the ways the flares were operated.
Requirements to restrict greenhouse gas emissions to meet environmental regulations affected the way these flares were operated. The flow rate of gas into the flares had been dramatically reduced.
Cracking occurred in 800HT Alloys
Metal temperatures of the flare reach between 600-750°C during low flow conditions, which is quite mild for heat resisting alloys. Therefore in this instance it wasn’t the heat that caused the alloy failure. Instead it was the fast cycling to lower temperatures during sudden surges in gas flow that resulted in cracking of the 800HT alloys.
Designed for high creep-rupture strength at high temperatures, the 800HT alloy has higher combined levels of aluminium and titanium than the original 800H alloy. Therefore 800HT can cause high levels of gamma prime phase to cause strain age cracking. Gamma prime is caused most during operation within 649°C, which is the regular operating conditions for the Indair flare design.
RA330 Considered for the Application
After a lengthy period of testing RA330 was considered for the application! It met all the identified requirements. The alloy needed to be a finer grain size than 800HT for thermal fatigue resistance, resist corrosion in the harsh conditions which the flare operates and resistant to the effects of strain aging just to name a few. RA330 is an alloy with excellent resistance to thermal fatigue and doesn’t age or embrittle. It is capable of withstanding lengthy exposure to temperatures up to 1149°C.
RA330 has been used for the Indair flare design for over 5 years and it continues to surpass all expectations.