An overhead system is one of the most vulnerable parts of a crude oil distillation unit because of the complexity of damage mechanisms. And even though the problems are well-understood by plant engineers and inspectors, the inspection process is almost as bad as an unplanned outage.
Typically, overhead units must be shut-down to allow inspectors to have rope-access to the piping for manual or Automatic Ultrasonic Testing (AUT) inspection. It is not unusual for a unit to be offline for up to two weeks while inspection is performed.
Additionally, the sheer number of onsite personnel required for either manual, or AUT inspection, presents safety and health challenges in today's pandemic environment.
That's why one refinery decided to see how the Rapid Ultrasonic Gridding (RUG) method could save time and money while delivering robust inspection data.
For this particular oil refinery in southern Louisiana, the inspection surface of fractionator piping was 240°F. Too hot for inspectors to work around, so shutting down the unit was previously the only option.
Gecko's TOKA 3 HotBot platform is specifically designed for high surface temperature inspections - up to 250°F, in fact. So, the Gecko Robotics Inspection Team (GRIT) was able to complete their inspection while the unit was still online.
Three piping sections of the fractionator overhead line were inspected - around 300 linear feet in total. Piping had OD measurements of 54" and 48". The GRIT team were made up of three Level II NDT certified inspectors. They completed the inspection in just three days, working 12-hour shifts; original scope by the plant had budgeted for four days to do the work. Gecko completed the work a day ahead of schedule.
Data. Data. Data.
In the course of the inspection, almost 500,000 data points (thickness measurements) were collected. Gecko's TOKA 3 HotBot collects multiple A-scan readings of a single point of an asset to verify accuracy and completes coverage at a speed that blows away single transducer, or AUT, inspections.
The TOKA 3 has a localization encoder which geolocates the position of the robot on the asset being inspected. RUG makes it easy to identify areas where the mechanical integrity of the asset requires immediate maintenance to remediate the problem. What's more, future inspections can be performed with confidence that the reference points will be maintained by plant elevations.
Turning Data Into Insight
Gecko Robotics' software platform uses robots as tools to capture data that enables top-notch reliability planning by providing interactive views through a digital portal. This Louisiana client was able to access and manipulate data views in 2D and 3D perspectives, online, on any device. Grids are intuitively color-coded to enable them to easily recognize relative thin areas in the assets wall thickness.
As always, Gecko delivered a summarized inspection report, post-inspection. What was interesting about this inspection was the positive report about the state of the piping assets. The client saw that immediate remediation measure were not necessary for the customer.
This gave the client two operational benefits - Confidence to continue to operate without requiring asset maintenance, and a data report to compare against future inspections for the calculation of asset-wide wear rates that differ at various locations.
Valuable insight, indeed.
How Success is Measured
The client's goal was to determine whether Gecko's RUG inspection technology could save time and money over previous inspection methods.
- 70% reduction in execution time
- 66% reduction in cost (over proposed cost of AUT/rope access inspection)
All while keeping the unit operating online.
The ability of Gecko to inspect the overhead lines at high temperatures opens up more opportunities for online refinery inspections, eliminating the need for additional or extended plant shutdowns.