Five steps to get ready for that upcoming in-line inspection tool run
- Your first step in ILI assessment is to understand the integrity threats associated with the pipeline.
- One of the main drivers for ILI tool runs is to meet regulatory requirements.
- Choosing the right vendor can be a difficult task due to the sheer number of ILI vendors in the industry.
- Your integrity assessment schedule should set priorities according to the reinspection interval and risk factors for each segment along the line.
While with a previous employer in the Houston area, I worked on an inline inspection tool run through a five-mile, eight-inch ethylene line – a run that could have gone seriously sideways.
In preparing for the run, we noted in the “lessons learned” from the previous deformation tool run in 2015, five years before, that there had been an unusually high number of starts and stops. This made us look at the line more closely, and we found that the line, built in the 1970s, had several wall-thickness transitions between 0.277” and 0.500”.
One of the recommendations in the “lessons learned” was to increase the flow rate during the next tool run, to avoid those starts and stops. It would also reduce the risk that one of those stops might turn out to be more permanent than we wanted — a stuck tool. Given that most of the pipeline runs under the Houston Ship Channel, in a High Consequence Area (HCA), risking a stuck tool is not acceptable, as the result would lead to a multi-million-dollar loss.
The lessons learned from the 2015 run suggested doubling the flowrate, as the 2015 MFL run did not indicate any issues at higher flowrates.
So we increased the flow rate to near double its usual rate. We placed our pig trackers along the line, launched our tool, and moved our crew to the receiving end. The run was expected to take about 90 minutes. Eventually, we heard something come into the receiving trap … but the pig trackers didn’t get a reading from the tool’s transmitter. We were thinking, “That’s not good.” About 30 minutes later, we heard a second “whoosh” sound from the trap.
We decommissioned the trap, unbolted it … and pulled out the tool, in two pieces.
Then we got to work figuring what went wrong, and how to do it better.
After receiving the inspection completion report from the tool vendor, we were able to see on the velocity-time plot that the tool stopped and lurched several times throughout the inspection. Overlaying these starts and stops with the wall-thickness transitions, we determined that the tool stopped and lurched at almost all transitions.
We determined that at one of the wall thickness transitions, the front drive cups of the tool popped off from the rest. The front part went on ahead, while the back part came along more slowly. We were lucky to get the whole tool back, rather than have part of it stuck along the way.
As part of our analysis, we looked at what was different on this run, compared to the previous run five years ago. The big difference was in the near doubling of the flow rate. The forces that resulted at the wall-thickness transitions were too much for the tool.
We decided that increasing the flow rate was still a good idea, to deal with the starts and stops that occurred before. But we didn’t need to put it so high. So, to do a second tool run that would provide useful data, we increased the flow rate to about 120% rather than 200%. This run was perfect. No starts or stops, good data – and the tool stayed in one piece.
What can go wrong without preparation
While many in-line tool runs go off without a hitch, they can have severe consequences when they go wrong.
ILI inspections are essential for meeting regulatory guidelines, and are also essential for an operator to be able to understand threats that may have been previously unknown. For example, if documentation is scarce for a specific pipeline, then an operator may be lacking important data on the segment that would help them fully understand the fleet of ILI technologies they should run in order to obtain that missing data. So, it is important to run a variety of tools, even if not regulation mandated.
Here are five ways preparation can help you achieve a successful inline inspection tool program.
- Understand the purpose and kinds of inline inspection
Your first step in ILI assessment is to understand the integrity threats associated with the pipeline. To get this information, consult with your Pipeline Integrity Engineer or Pipeline Integrity SME. Identifying applicable threats will help you decide which tools to run. At a minimum, it is required to run both deformation and corrosion tools. However, there may be engineering justification to run more. For example, a pipeline with pre-1958 ERW pipe may be subject to crack-like features associated with the long seam. If that is the case, regulatory agencies require the operator to use a tool capable of detecting crack-like anomalies.
Once you’ve understood the threats, it’s time to determine which kinds of ILI tool runs will get you the information you need. Three of the factors that determine success are:
- Your knowledge of the pipeline’s integrity history
- Being current on regulatory requirements
- Forming a team capable of fulfilling the necessary requirements
- Meet regulatory standards
One of the main drivers for ILI tool runs is to meet regulatory requirements. These differ between lines for gases and liquids – and this post focuses on liquid pipelines.
One of the requirements to bear in mind is that pipeline operators must have in place an Integrity Management Program that is adequate for recognizing, understanding and mitigating pipeline integrity threats.
Sometimes, a line isn’t piggable – perhaps the pipeline’s geometry is not suitable for a pig to traverse. In such cases, regulatory agencies require that an operator assess their pipeline’s integrity in another form such as hydrostatic pressure testing or External Corrosion Direct Assessment (ECDA).
- Choosing the right vendor
In our experience, choosing the right vendor can be a difficult task due to the sheer number of ILI vendors in the industry. It is important to choose a vendor based on your specific needs, but it is also important to look outside of whoever provides the lowest bid. While investigating vendors, be sure to include in your assessment the responsiveness of the vendor, tool anomaly detection capabilities, quality of reports, Data Analyst qualifications, general reputation, and pricing.
Your due diligence should include making sure the tools the vendor can provide will be able to navigate your pipeline. Factors may include minimum bend radius, non-piggable valves, stopples, minimum bore, etc. In addition, it is important to understand the length of each tool, as other projects to extend or modify traps may need to be budgeted, to allow the tool to be launched and/or received.
- Plan your inspections
Your integrity assessment schedule should set priorities according to the reinspection interval and risk factors for each segment along the line.
In planning each run, you should meet with the project stakeholders — operations personnel, staff in the Operations Control Center, Engineering, and contractors (which might include tool tracking, vac truck, flaring, and tool vendor).
You may have heard someone say that an MFL tool is best cleaning pig out there – and also the most expensive! Avoid bad runs by ensuring the line is clean prior to inspection. Some lines require extensive cleaning pig runs before ILI tools can perform effectively, others stay clean enough that a gauge pig will do the trick. Know which type your line is before putting the technology in.
Remember that the pig trackers may need access to private property, and this should be discussed with the landowner prior to the tool run.
Also, remember to discuss with stakeholders, and incorporate into procedures, how to bypass stations that may be fed off the mainline. For example, pump stations may need to be bypassed to ensure the tool does not nose into the suction piping.
- Engage with a reputable third-party engineering firm
Ways third-party engineering firms can help you include:
- They have specialized know-how regarding integrity inspections, and the ability to relate to the tool vendor and other contractors
- They can help you keep track of the work required to meet PHMSA requirements, so you’re not rushing to meet a PHMSA inspection deadline
- They’re able to handle the whole project, so the operator can focus on business as usual
- They have experience in generating repair plans and recommendations that can dovetail into your operations and maintenance work planning
To learn more about how you can prepare for ILI tool runs that are problem-free and get you the results you want, please reach out to us.
Credit: Photo includes a ROSEN ILI tool.