Inspectioneering Journal

Inspection of Individual Serpentine Coils in Fired Heaters Connected to Common Headers

By Richard D. Roberts at Quest Integrity Group. This article appears in the May/June 2013 issue of Inspectioneering Journal.


Refineries and chemical plants own and operate numerous process heaters (e.g. gas reformers, CCRs, etc.) as part of the standard assets throughout the facilities. Many heater coil configuration designs are flanged at both ends; however, there are also coil designs which contain common headers, linking the individual coil passes together at the inlet, outlet, or even at both ends in some cases (see Figures 1 and 2). Plant inspectors are presented with a significant challenge to perform the necessary condition assessment inspections on serpentine coils, and common headers complicate this further by adding additional challenges for decoking and inspection processes. For more than a decade, the use of intelligent or smart pigs has become a standard practice when inspecting regular flanged coil configurations, which do not contain common headers. However, with new common header snorkel delivery systems, these particular heater designs are also able to be inspected using the same approach.

Figure 1. Heater coil configurations.
Figure 1. Heater coil configurations.

Figure 2. Heater coil configurations.
Figure 2. Heater coil configurations.

As described in a previous article in the November/December 2012 issue of Inspectioneering Journal (“New Technology Allows Access to Coils with Common Headers in the Process Industry”), advanced engineering firms and mechanical decoking companies have developed unique common header snorkel delivery systems enabling both cleaning and inspection of connected serpentine coils.1 Once access to the headers’ interior has been provided, by removing the blind flange or cutting off the bonnet, these systems are then temporarily inserted into the common header while the fired heater is off-line (see Figures 3 and 4), and guide mechanical decoking pigs and intelligent pigs into the heater’s individual coil passes. The delivery systems are modular by design, eliminating the challenges associated with accessing individual coils, and they can be attached to short or long common headers.

Figure 3. The snorkel system being inserted into a common header.
Figure 3. The snorkel system being inserted into a common header.

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Comments and Discussion

Posted by Tawfik Mohamed on January 23, 2016
Thank you Richard for the interesting article, i... Log in or register to read the rest of this comment.

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