Inspectioneering Journal

Reliability of Coke Drums

Part 1

By Eivind Johnsen at DNV Inc., Lynne Kaley, Director of Reliability Strategy at Pinnacle, and Andy Tallin at DNV Inc. This article appears in the November/December 1996 issue of Inspectioneering Journal.
This article is part one of a 2-part series on Coke Drum Reliability.
Part 1Part 2

Petroleum coke production is an important source of revenue for many refineries. While coking units were initially constructed to deal with a waste product, these units are now of significant economic value.

Worldwide, an estimated 3.8 million barrels of petroleum coke are produced per day. Figure 1 shows the distribution of coke production; nearly 50% of the production is concentrated in the US. Delayed coking is the most common coking process, accounting for as much 3.3 MMbpd.

Figure 1- Coking capacity worldwide
Figure 1. Coking capacity worldwide

Coke drums are an essential component in the delayed coking process. These drums are used to separate petroleum coke from lighter hydrocarbons. Many drums have reliability problems. Because the drums are central to the coking process, poor drum reliability can lead to frequent shutdowns and low productivity.

Coke drums are constructed of a vertical cylindrical shell with an elliptical top and a conical bottom. They range from 60' to 80' in height and 15' to 30' in diameter. Skirts, attached near the shell to cone weld area, are used to support the drums. Most coke drums are made of C-1/2 Mo or Cr-Mo steel and internally clad with stainless steel.


In delayed coking, coke drums are operated in pairs where only one drum is filled at a time. Coking cycles, from fill start to fill start, last between 24 and 48 hours.


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