New Technology Allows Access to Coils with Common Headers in the Process Industry
As seen in the Nov/Dec 2012 issue of Inspectioneering Journal.
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IntroductionVarious 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 ChallengesPrior 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.
Common Header Delivery System SolutionThe common header systems are designed to be modular, allowing heaters containing either short or long headers to be addressed. Designing the system in small compact sections that can be assembled as the unit is gradually inserted into the header addresses safety, installation flexibility, and ease of use concerns.
The systems contain very few touch points which actually come in contact with the header’s interior surface, ensuring the header is not damaged during the operation. Rounded surfaces on the support legs provide low friction rolling for easy maneuvering down the header from individual coil to coil. These legs support the system from the underside, while rubber seals are used to mate up with the individual heater passes.
As the header delivery system is inserted into the common header, cameras provide real-time feedback about physical positioning in relationship to the individual coil branching off the header (see Figure 2). Once the system nears the individual coil with which it intends to mate up, the camera allows the operator to precisely align the mating face directly with the individual coil. Once the alignment has taken place, the hydraulic legs then anchor the system in place to ensure a water-tight fit.
The upstream end of the snorkel system is connected via flexible hoses or hard-line piping to the mechanical decoking contractor’s launcher, receiver and pumps, allowing both mechanical decoking pigs and intelligent inspection pigs to be
delivered into the individual heater coils, much like standard heater coil configurations. See Figure 3.
Once the individual serpentine coils are cleaned and inspected, the system’s hydraulic arms retract, allowing the rubber seal to detach from the individual coil which branches off the common header. The system is then inserted further into the header until it reaches the next coil, repositioning itself again as previously described. The delivery system continues in this manner until the cleaning and inspection has been completed for all of the heater coils.
SummaryPlant operators who have heaters containing common headers now have the same cleaning and inspection options that
were previously only available for those heaters which did not contain common headers. Considering the limited access to
the external surface of heater coils, this is a significant advancement in the industry. The common header delivery systems reduce risk of heater failure due to individual coil failure caused by damage mechanisms such as corrosion, erosion and creep strain.
About the AuthorRichard Roberts, Vice President and General Manager, Quest Integrity Group
Rich Roberts began his career in the oilfields of Alaska at Arco Petroleum in 1985, where he was involved in a massive corrosion monitoring and prevention program encompassing critical assets such as pipelines, pressure vessels, tanks and well heads. After departing Alaska in 1992, Mr. Roberts helped implement specialized NDE/T division start-ups for various engineering and service companies within North America, such as ABB/Amdata, Combustion Engineering and CTI/Tuboscope. In 1995, Quest Integrated recruited Mr. Roberts to establish a Field Services Division charged with developing and applying its proprietary NDE platforms, LOTIS® and FTIS™. When Quest Integrated’s Field Service Division and TruTec Services merged to create Quest TruTec in 2004, Mr. Roberts assumed leadership for Quest TruTec’s Condition Assessment Division. Today at Quest Integrity, Mr. Roberts leads both operations and engineering activities for the Inspection Division and coordinates Refining industry-targeted strategic initiatives. Mr. Roberts received his A.S. in NDE from the University of Alaska and his B.S. in Welding Technology from Ohio State University.