Inspection technology addresses corrosion under insulation

In the current business climate, oil and gas operators are striving to extend the life of their assets and associated plants. Finding solutions to asset integrity issues that avoid lengthy downtimes is a fundamental element of any maintenance schedule.

Further complexities are added as offshore operators begin to work at greater depths and increased pressures, which will put additional strain on assets and create a greater number of challenges to overcome when testing their integrity.

Various methods of non-destructive examination are now commonplace in the inspection of process system pipework.
Traditionally, to carry out such an inspection, sample areas would have to be identified within the piping circuit where insulation had to be removed and inspections carried out, which can be time-consuming, costly, and ineffective. Potential defects are not always identified, and disturbing sound insulation can compromise integrity.

New X-ray technology has resulted in a safer and more efficient pipe scanner than with traditional systems. (Images courtesy of RBG)

RBG has identified the issues operators are facing. To address the issues, the company has introduced its real-time digital imaging system to detect corrosion under insulation (CUI), a system which recently was used on a platform process piping system for a major deepwater Gulf of Mexico (GoM) operator.

The advanced technology, which has been added to the company’s non-destructive examination service, uses low-energy X-rays and is a non-intrusive method of checking insulated pipework and associated equipment for corrosion.

In a more versatile process, the real-time digital imaging system allows technicians to scan much larger areas of piping circuits quickly and identify problem sections without shutting down production. Upon detection, they can be addressed effectively and efficiently with a targeted maintenance plan. In turn, this helps to maintain long-term asset integrity by avoiding issues associated with selective testing, such as water ingress.

System methodology
The lightweight system uses low-energy X-rays to identify corroded areas. Due to the low radiation levels, only a reduced area of operation has to be cordoned off to carry out the procedure compared with conventional radiography techniques, which often are used for this type of work. Operations can continue with minimal disruption to ongoing adjacent activity.

Unlike previous X-ray systems, this system projects real-time digital video images onto a handheld LCD and head-mounted display at 30 frames/second. The image is continuously presented, allowing rapid in-motion scanning of pipes through a range of material densities. These include carbon/stainless steel, cast iron products, aluminum, plastics, and composite materials.

A new highly sensitive imager, which minimizes the required levels of X-ray energy, combined with the tight beam collimation and shielding, gives the system a reduced controlled area. This ensures it is both safe to hand-hold and use in areas of continued operation with far less evacuation of personnel and minimal disruption to other activities, following the principles of ALARP.

Technicians use RBG’s real-time digital imaging system to detect corrosion under insulation.

A third party can view these displays live using complimentary metal-oxide-semiconductor (CMOS) technology, which offers dramatic improvements over the more commonly used charge-coupled device (CCD) digital systems now prevalent throughout the non-destructive examination industry. CMOS differs from current digital systems for several reasons. First, the pixels that constitute the detection panels have a larger detection surface compared to a CCD pixel. Secondly, the area to be hit by photons is greater because of the way the CMOS pixels are wired.

Each pixel on the CMOS thin film detector has its own amplifier, whereas CCD panels have amplifiers connected to multiple pixels in series, meaning that the resolution and clarity with CMOS arrays now exceed traditional film radiography. The system also offers safety benefits by eliminating processing chemicals and waste manifestation. The sensitivity of the panels means the radiation exposure levels are considerably reduced, and the unit is further enhanced by a failsafe X-ray on/off trigger and removable lockout key.

Due to the portable nature of the system, it can be combined with RBG’s rope access capability, allowing for easy access to elevated pipework systems and connections on offshore platforms as well as petrochemical plants without scaffolding.

RBG was contracted to undertake inspection of a carbon steel piping system in the GoM to determine the location of internal and external corrosion or water ingress. Using the advanced radiation technique allowed the operator to identify the defects and prepare a maintenance plan without the associated cost of removing sample sections of insulation. Working in tandem with rope access resulted in completion of the project four weeks ahead of schedule.

The system has proven successful in North America due to its fit with operator maintenance schedules, its efficiency when compared to existing techniques, and increased safety measures. By completing the work in half the time of more traditional methods, operators will avoid lengthy downtimes or work in specific sections, which would involve regular shut-down periods. Increased cost savings also are achieved due to the shorter duration and because it only requires a two-person team.