Sujal Surendran - Reliance Industries Ltd.
Reliance has 9 Coker Heaters currently operating at Jamnagar, Gujarat. This paper describes the experience with Coker heater tubes at DTA Refinery which have been in service for the last 20 years and the replacement strategy adopted.
In DTA Coker furnaces, a gradual thickness loss from the inner wall has been observed in radiant section tubes of the heater. Scrapper pigging is being carried out periodically for removal of Coke deposits inside the coils. Inspection has revealed significant thickness loss in Alloy steel tubes over a period. The thickness loss was mainly attributed to removal of the protective Sulphide layer (due to high temperature Sulfidation) by scrapper pigging which exposed fresh metal surface to Sulfidation. Based on the experience, an in-house strategy has been developed to ensure reliability of heater tubes in DTA Coker Heaters. This paper lists out the causes of deterioration of Heater tube thickness, Inspection strategy for heater coils, systematic approach adopted for replacement of tubes considering available planned outages without compromising on integrity.
The paper also outlines the other parallel approaches like conventional API RP 530 calculations and Fitness for Service Assessment (FFS) that has been adopted to decide the retiring thickness criterion for Coker furnace coils.