Part 2: Summary of Practice thru Procedures
Some days it seems like an annoying little toddler lives in my head chanting “How, why, why, why, why, how?????” Charles Steinmetz a mathematician, engineer and inventor who made the expansion of alternating current possible in the United States is quoted as saying “No man really becomes a fool until he stops asking questions.” Today, I have questions and lots of them.
When new industry news comes out, my mind instantly starts dissecting how this news might impact project construction and field services. As I read through the GRI-GM32, questions came fast and hard amidst few answers. One of my deep concerns is that this Standard Practice has the potential to generate exorbitant additional cost depending on how some of the following questions are clarified. It is vitally important to understand the full purposed processes and procedures surrounding this Standard. If indeed the purposed practice does open up substantial cost liabilities, then the industry will have to define who is responsible for these liabilities.
With all the questions and concerns voiced in part 1&2 of this blog it may seem that I am against “data acquisition welding devices”. Actually, I am very excited to see them put into use; however, I want to see a clear plan and standardized practice that can be practically implemented in the field. Asking the right questions is a part of creating a solid plan.
So, as you read through the blog, keep asking yourself questions – we all need to work together from our various viewpoints to bring healthy successful change.
4. Summary of Practice: “…Thus, by observation of the continuous signal output of each variable the operator can make periodic and timely adjustments. In doing so, it is expected that the seaming process stays within the material specific and site-specific acceptable seaming bubble or seaming window. Such recordings also show continuity of seams without gaps or other anomalies.”
Data acquisition welding devices significantly assist the intuition of the operator by giving visual data of the three variables on a continuous basis. Response to changes in any or all of the outputs can be gradual or sudden, and is generally accomplished by varying the device’s speed or stopping the process entirely until the situation is remedied.”
- To what standard/baseline are the values being compared to? Without a standard or calibration, these are simply numbers – there needs to be some correlation that these numbers are accurate in order to successfully plot them in a window.
- At what interval is the data being obtained? Is it truly continuous as suggested in this text?
- For the operator to make adjustments, the operator needs to be present, manning the machine during the welding process. It is not uncommon to see operators ten or more feet away, sometimes cleaning/preparing the seams, or to even be fully absent taking a restroom break.
- How is it verified that adjusting the welding machine actually keeps the seaming process within the seaming bubble as “expected”? Wouldn’t it seem the best way to meet this expectation is to take the human component out of this by using the closed-loop system?
5. Significance and Use: “The goal of such data acquisition welders, as just described, is to document the seaming parameter data and identify deficiencies or lack thereof (as typically assessed by nondestructive or destructive seam tests). This is done by using data to verify positive seam quality and/or deficiencies.”
- Ideally, “deficiencies” would be identified prior to seam completion and not after the completion of an entire seam if an attentive operator and QA are present.
- How are we to use the data to “verify positive seam quality and/or deficiencies”? This seems an unlikely result given we have no training requirements, no equipment requirements for accuracy of welding or data recording, and no formal welding “bubble”. Looking at a graph with all of these variables missing may look good on paper but be totally suspect in reality.
- Who is verifying and on what timeline? Engineer, QA, Welder, Regulatory Agent?
- If verified after the seam is completed, then how long afterwards? Will material already be covered? Will the crew still be on-site?
- Does this data need to be included in certification reports? Can this data be used to force site owners to re-open covered membrane for additional inspection because the data presented questions? What are the cost implications of delayed and/or post construction verification? This thought may seem far-fetched, but it is a reality, especially if there is no formal training on reading the data output. If the regulatory agency comes up with a different interpretation than the installer and CQA firm, there will be questions!
- If QA’s are reviewing the data during seaming, will additional QA technicians be required to provide adequate cover for all welders and other job activities?
6a. Procedure with Conventional Welding Devices: “The issue with such conventional welding devices is that an operator never precisely knows where the outputs are within the window or bubble.”
- I agree with this statement. Without any standard/calibration, there is absolutely no way to know if the machine is operating within the window even though the settings may indicate that, without tolerances there are no guarantees. I believe this same problem persists with the data acquisition devices if there is no calibration.
- Assume an operator performs a passing trial weld per the recommendation in this section of the document but does not realize the speed is on the fast side of the acceptable window, going down a slope could push the actual welding parameters outside the acceptable window (open-loop system) without the operator (or anyone else for that matter) ever realizing there is an issue.
6b Calibration: “Note 10: Critical in the proper functioning of such welding devices is to have initial and ongoing ‘machine calibration’ practices. The device manufacturer’s instructions must be rigorously followed.”
- Where are the requirements for calibration of the equipment? Note 10 in section 6b of the document contains a blurb (above text) about following device manufacturer’s instructions, but I have never seen this requirement to date in my 30 years in the industry. Sure, the readout may say the machine is operating at x temperature, y speed and z pressure, but how is that confirmed, and to what standard is it being compared? I’ve seen two or more fusion machines (open-loop) set on a certain speed (each set on same speed) and they obviously move at different rates on the same setting – and they seemingly move at different rates depending on the condition (upslope travel versus downslope travel versus flat surfaces). Without some point of reference such as a calibration, the data is somewhat meaningless unless the point is just to show there are no variations in the data throughout the weld – but if that is the case, it still does not mean it was welded within the “bubble”.
- Along the theme of calibration, what accuracy or tolerances do these machines have to maintain?
- Additionally, what are the requirements for the tolerances of the recording devices? It would seem fairly useless to record data if the recording device accuracy is not held to some type of standard.
7. Summary: “Rates of seam failures have been reduced over time from quite high percentages (10% or more) down to approximately 2% based on laboratory testing of destructive seam samples (recent IFAI data).”
- I tend to find this statement totally absurd based on CQAS experiences this year alone. On a recent project where we performed QA, the fusion failure rate was 13.3% and an extrusion failure rate of 22.2% on just original samples. A well-known installation firm performed the project with a seasoned foreman.
- Destructive failure rates are subject to considerable manipulation on how the data is presented and obtained (sampling strategies), and if field failures are not included, as would be suspected based on the term “laboratory”, the failure rate number is already skewed.
- My biggest concern here is that people see numbers presented and make decisions based on them, without a true understanding of what is truly behind the numbers. An in-depth look at destructive sample failure rates will be the topic of an upcoming blog.
Overall, I believe some kinks need to be worked out for us to move forward and have a workable plan for data recording that actually ensures the quality is there (some of which applies to current machines without data acquisition technology) and the current version of GM-32 is not the solution – but at least it is a foundation from which to build. Ultimately, I believe the data recording technology is another huge advance for obtaining the long-term quality owners are looking for in their geosynthetics installation. My speculation is that data recording will ultimately drive quality as manufacturers are forced to hold tighter thickness tolerances as a result of the data being obtained by these devices.
As always, I welcome your feedback and comments!
Link to GRI-GM32: https://geosynthetic-institute.org/grispecs/gm32.pdf
