An Investigation on the Causes of Failure in A210 Carbon Steel Boiler Tubes in an Oil Refinery
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CASE HISTORY—PEER-REVIEWED
An Investigation on the Causes of Failure in A210 Carbon Steel Boiler Tubes in an Oil Refinery Hamed Hoseiny . Mohammad Shayegani Akmal
Submitted: 16 January 2018 / in revised form: 17 April 2018 / Published online: 31 May 2018 ASM International 2018
Abstract As boilers are subjected to corrosive streams and harsh operating conditions, their tubes are susceptible to corrosion and failure by different damage mechanisms. In the current study, the causes of cracking and failure of connection tubes of a boiler header are studied. These tubes were connected between the primary and secondary headers of the boiler and according to the design information were constructed of ASTM A210-A1 carbon steel. There were two cracked tubes wherein one of them had a crack in a weld HAZ region and another had a crack in the base material. To investigate the failure, different microscopical and analytical techniques such as SEM and mechanical tests were used. The results of analysis showed that the material of construction was in accordance with the design specification. Considering the cracks dagger-shaped appearance, it was concluded that thermal fatigue due to the operation conditions and utilization of water spray cooling technique was the main cause of the failure. Keywords Failure analysis High-temperature corrosion Thermal fatigue Carbon steel Boiler
Introduction Boilers or steam generation equipment is one of the most fundamental systems of a refinery or power plant. Failure
H. Hoseiny M. Shayegani Akmal (&) Corrosion Research Group, Research Institute of Petroleum Industry (RIPI), Tehran, Iran e-mail: [email protected]
due to corrosion in steam generation equipment is a major threat to the integrity of pressurized equipment, particularly in the oil and gas industries [1, 2]. The chemistry of the water, alloy composition and operational conditions have a significant influence on the rate and mechanism of corrosion of alloys used in construction of steam generators. The corrosion morphology can also vary from general to localized corrosion, i.e. pitting or cracking, depending on the design and operating conditions [3, 4]. Ferritic steels are typically used in heat exchanger tubes in different industries such as power plants and refineries due to their sufficient strength and excellent resistance to high temperature, pressurized water or steam [5]. However, due to susceptibility of the weldments in these alloys to corrosion, most of the failures take place in the weld and heat-affected zone (HAZ) regions [6, 7]. In addition, corrosion rate can significantly be higher on the fireside of tubes due to high temperatures and erosion corrosion attack [8]. Mechanically assisted damage such as thermal fatigue at the waterside or fireside is another failure mechanism observed in tubes subjected to cyclic stress during operation [4, 9]. Corrosion fatigue normally occurs in wall tubes, reheater tubes, superheater tubes, economizer tubes, deaerators, and the end of the membrane on water wall tubing
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