Failure Analysis of Heat Exchanger Using Internal Rotary Inspection System (IRIS)

Abstract

Retubing of a heat exchanger always plays a critical role in oil and gas plants. Normally, many end-users prefer to do full retubing rather than partial retubing during maintenance or shutdown in order to achieve more efficiency. But in case of alloy steel tube-based heat exchanger, partial retubing is preferred because cost of alloy steel tubes is ten times higher than that of the carbon steel tubes. In this research, low-efficiency heat exchanger was selected since it requires full retubing (maintenance) due to severe in-service tube thickness loss and low efficiency as per end-user. Tube material was Inconel SB 163-800H, and the quantity of tubes was 286. Among numerous advanced NDT strategies used to minimize downtime arising from catastrophic failures induced by erosion/corrosion or mechanical loss sustained during the operating period, internal rotating inspection was chosen. This approach identifies a lack of wall thickness reduction arising from deterioration, wear, pitting (ID & OD) and corrosion. After IRIS inspection method was carried out, it was easy to categorize how many tubes are exactly defective and exchanger requires partial retubing or full retubing which finds huge savings and reduction in maintenance cost and time. IRIS inspection method also provides the distribution of tubes by wall thickness loss of total 286 tubes in the heat exchanger and retubing of heat exchanger will be further continued to achieve more efficiency.