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Inspectioneering Journal

New Technology Allows Access to Coils with Common Headers in the Process Industry

By Richard D. Roberts at Quest Integrity Group. This article appears in the November/December 2012 issue of Inspectioneering Journal

Introduction

Various fired heater designs in refineries and chemical plants contain common headers (e.g. Arbor coil configurations, CCRs, etc.) as part of their overall serpentine coil design. Accessing the interior of individual coils through the common header is challenging; however, advanced engineering firms and mechanical decoking companies have developed unique common header snorkel delivery systems. These systems are temporarily inserted into the common header while the unit is offline, guiding both mechanical decoking pigs and intelligent pigs into the individual heater coils. 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.

Common headers come in a broad range of diameters, lengths and shapes which were taken into consideration during the development of these delivery units. The delivery systems have enabled plant engineers and inspectors to take advantage of mechanical decoking to clean the coils and intelligent pigging technology to inspect coils which were previously inaccessible.

Common Header Challenges

Prior to the development of header delivery systems, plant owners and operators had to physically cut each individual coil near the common header and weld on temporary flanges if they wanted to utilize mechanical cleaning and intelligent inspection pigs. The time and cost to make these modifications was prohibitive, resulting in the majority of plants electing not to carry out mechanical decoking or intelligent pigging. With the recent development and availability of header delivery technology, engineers are now reviewing and prioritizing heaters containing common headers for cleaning and inspection during upcoming turnarounds.

In order for a plant to take advantage of the common header delivery systems, engineers must first thoroughly review each heater’s common header design to determine access. Some common header systems already contain blind flanges at one end allowing access to the interior, however others do not. For those designs which do not contain a blind flange, it is common for a bonnet to be welded in its place. This bonnet must be removed to access the header’s interior. Once the cleaning and inspection efforts are complete, the bonnet can be replaced with a blind flange, making future access for cleaning and inspection less challenging.

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