In another post, we discussed how asset owners do not give sufficient weight to the probability of detection (POD) in their asset integrity management programs. Yet, the continued operation of critical assets and the prevention of failures depends on correctly identifying damage, modeling, and predicting corrosion rates.
This relies on the effectiveness of an inspection methodology for a given piece of equipment. Understanding maximum POD for an inspection method and understanding the max POD in a particular inspection is vital. The inspection plan is one critical area which impacts the POD.
Here is what a very simple “typical” inspection plan often looks like:
- The code “says,” or it comes time to inspect something and someone decides, “We need to inspect XYZ piece of equipment.”
- A work order is issued to an inspection contractor.
- They use whatever method they have used before, get a reading, issue their report, and move on to the next job.
There are identifiable and correctable limitations, as this approach:
- Assumes we are inspecting in the right place to begin with. In many cases CML locations have not been modified in 10+ years.
- Assumes that we know and understand which damage mechanism(s) we are looking for.
- Assumes that the technician understands and is able find said damage mechanism when present.
- Assumes the gauge or technology chosen is appropriate for the given task.
- Assumes that the method of reporting will provide what the inspector or engineer is looking for.
As you can see, a lot is assumed. However, quality inspection planning eliminates as many assumptions as possible. This yields a higher POD and therefore higher reliability of the plant and equipment.
Let’s go a little more in-depth with each of the factors of a quality program.
The inspection plan and the amount of real estate covered. Are we taking into consideration historical bad actors, the age of equipment, IOW excursions, change in materials?? What exact flaws are we looking for? How thorough can we get within the allocated budget? Are we using available screening technologies in combination with volumetric to maximize POD or are we doing it the way that it “has always been done?”
The technology and inspection equipment you are using, including calibration. Is the inspection equipment adequate and in good working order? What are the sensitivities and limitations of a particular piece of technology?
The process and procedures used to carry out the inspection and their consistency.Do we understand the damage mechanism? Has the technician demonstrated that they can find that type of damage? In most cases the answer is no. Technicians have been certified to ASNT level 2 or 3 but have rarely demonstrated their ability on ALL important and high consequence damage mechanisms.
The testing environment, including weather and other stressors such as working at height and/or extreme heat or cold. At the end of the day, human beings operate all of our modern equipment and are prone to performance variations given increasing stressors. Has this been factored in when considering the probability of detecting damage, especially when working on high-consequence-of-failure equipment? Are there any hazards in the environment which can skew results or prevent 100 percent coverage of what our inspection plan calls for? Are there any potential safety issues which need to be addressed first before techs can go in, so that that technician has the highest opportunity to be successful? Have all the stressors been reduced as much as possible and where not, has the reliability of the inspection results been appropriately discounted?
The training and ability of the technicians performing the tests, including physical condition, experience with a particular damage mechanism, mental state, etc. What kind of training and experience do the vendor’s technicians have? How thorough and reliable are they based on their history?
When you consider all of these factors together, it paints a picture of the quality of inspection. The probability of actually detecting damage mechanisms, and therefore controlling them and ensuring plant reliability and personnel safety, is a multiple of these. Effort spent in optimizing each of the factors therefore leads to a better end inspection.
The final piece of the puzzle is the clarity of the reports issued and whether they deliver actionable insights into the condition of components to the end user – which is the reason you are inspecting in the first place.
This is not an indictment of our industry inspection personnel. The vast majority are very conscientious and deeply committed to providing a quality product. The purpose of this post is to raise the awareness on how we can empower our people to produce accurate results, which will increase the reliability of our assets and facilities.
Please reach out with any questions or to talk to one of our inspection specialists.
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