Inspecting fired heaters with plug headers: obtaining complete data to maximise life

Published by Angharad Lock, Digital Assistant Editor
Hydrocarbon Engineering, Friday, 20 November 2015 09:30

Introduction

The practice of employing ultrasonic-based intelligent pig technology to inspect serpentine coils in fired heaters is commonly implemented by refinery operators industry-wide. This method of inspection has proven invaluable in providing precise and comprehensive inspection results, enabling plant operators to avoid costly plant shutdowns or unanticipated failures. In years past, the presence of plug headers (mule ears) within heater coils has limited the inspection capabilities of ultrasonic-based intelligent pigs. However, recent advances in this technology have allowed for the inspection of fired heater coils that include plug headers, without requiring coil modifications such as radial or deflector inserts.

Market demand and technology advancements

Conventional NDT inspection services cannot inspect the full piping coil and are frequently unable to access coils located in a convection section of the heater. In response to the industry need for high quality fired heater inspection capability, Quest Integrity’s Furnace Tube Inspection System, or FTIS™, was developed, and has recently extended the benefits of ultrasonic intelligent pigging to heater coils containing plug headers – without the need for time consuming or expensive coil modifications such as radial or deflector inserts. This significant advancement in technology further ensures the inspection of up to 100% of the entire piping coil, while providing excellent data quality and accuracy.

The technology

The ultrasonic-based intelligent pig technology addresses the damage mechanisms associated with corrosion, pitting, erosion, fretting (mechanical damage), interior and exterior wall thinning, deformations (e.g. creep, swelling, ovality, denting and bulging), axial and circumferential flaws, and coke or scale build-up. Unlike typical NDT inspection methods, the UT-based pigging technology provides a comprehensive assessment of both the internal and external condition of a piping coil.

During a standard FTIS inspection, the UT-based pigging tool travels the interior of the serpentine coil through a liquid medium, and yields coverage of both the convection and radiant sections of coil, providing up to 100% circumferential and axial coverage of coil components, utilizing 48 to 168 ultrasonic sensors. The data gathered during the inspection can then be used to perform remaining life assessments and fitness-for-service to assess overall coil condition, allowing plant operations to determine remnant life and avoid costly delays.

Inspection data display

Data collected during the inspection run is analysed in Quest Integrity’s proprietary software, LifeQuest™ Heater. The software imaging allows for the display of both 2D and 3D views of the piping, ensuring full visibility of flaws throughout the entire piping system. The viewing optimisation of LifeQuest Heater also provides exceptional graphical visibility of coil flaws (see Figures 1 and 2, respectively).

LifeQuest Heater provides a complete analysis and assessment of a heater coil, utilising API 579 industry standards. In addition to assessing current internal piping conditions, the software maintains the ability to manually or automatically import past operating conditions, inspection histories, and materials information, providing the industry’s most comprehensive analysis of coil life.

Figure 1. Wall Thickness Data

Figure 2. Remaining Life Data

Inspection of fired heaters with plug headers

Fired heaters, such as coker heaters, may contain plug headers (see Figure 3) in order to allow access to the serpentine coil interior without cutting off a return bend. This access is sometimes necessary in order to achieve recirculation in the event that flow through the coil becomes blocked, and circulation is not achievable at the optimal flow rate. Historically, the presence of plug headers has posed a major challenge to the inspection process due to difficulty in navigating the fittings. In past years, plant operators have needed to install specially shaped radial inserts in order for an inspection tool to navigate through a heater with plug headers.

Advances in Quest Integrity’s technology have increased the capabilities of the tool and extended the benefits of ultrasonic intelligent pigging to heater coils containing plug headers – without the need for radial inserts. This technology advancement opens up critical heaters in fouling services, such as cokers. Now, creep and metal loss damage mechanisms commonly seen in these services can be more accurately quantified, allowing for fitness-for-service and tube retirement planning.

Conclusion

The use of ultrasonic-based pigging technology in the inspection of serpentine coils is vitally important for the life of a fired heater. With the advancement of Quest Integrity’s FTIS technology, operations managers can be certain that the comprehensive inspection of their fired heaters provides up to 100% analysis of all damage mechanisms within coils.

FTIS is an industry-proven technology that, to date, has been used to inspect thousands of heaters globally. The new FTIS capability has undergone extensive testing in both operator-owned and designed facilities, ensuring the continued accuracy, confidence and overall value of the intelligent pigging service. With the additional advancements of the pigging tool to accurately and completely inspect heater coils with plug headers, without the need for radial inserts, operators can be confident in the ease and accuracy of intelligent pig inspections.

Figure 3. Plug Header