was successfully added to your cart.

Cart

GRI-GM32: No Pathway to Practical Implementation

By October 23, 2019 Uncategorized

Part 1: Scope & Terminology

Let me start by stating that I appreciate the GRI and the work they do within the industry – I’ve met both Dr. George Koerner and Dr. Bob Koerner and greatly respect them both.  

I often enjoy watching both George and Bob engage in much needed industry debate as I firmly believe we have the same goals of pushing our industry to a better place.  As I offer feedback today on the GRI-GM32, it is done with the sincere belief that this information is critical to moving our industry forward.

The purpose of a standard practice is to provide accurate and specific guidance to the user for the “typical/usual” way something should be done in a prescribed situation.  As I read through the recently released GRI-GM32 (found here), this standard practice not only falls significantly short of providing accurate guidance, it misses some key concepts, and has me asking more questions than I found answers to!

I am sharing some of these questions and concerns with you in parts 1 & 2 of this blog.  For ease of reference I refer to the numerical section and include an italicized quote from the GRI-GM32 ahead of most comments/questions.

Some of the eye-popping, thought-provoking questions I come up with when reading through this document are:

1.2 Scope: “This particular standard, leading to a data acquisition hot wedge welding device, allows for the continuous monitoring and recording of these three variables. Thus, the operator can make adjustments based on the appropriate recorded values for seaming with that specific device.”

There are several questions here:

  1. What does appropriate recorded values mean? Who determines what is appropriate? When are these values evaluated and when do the settings get changed?
  2. Even with this new method it seems the operator is still responsible for the “ongoing adjustments” unless there is some kind of specific formula for changes?
  3. The installer is providing the guidance for welding variables that are acceptable? To me, this data potentially should come from some sort of formal testing and recommendations by the Manufacturer and/or Engineer and should be based on information other than acceptable seam destructive tests.  While a “seaming bubble” is presented later in the document, there is no information given on what constitutes a good seam.  There are plenty of seams that pass destructive testing, but are compromising the long-term viability of the seam by overheating and thinning the seam/adjacent areas that increases the risk of stress-cracking. (We will talk about who holds the liability for these compromised seams in another blog.)
  4. What are the experience, education, and/or training requirements for this technician who is now allowed to adjust the machine during welding, potentially without additional trial welds?
  5. What are the experience/training requirements for the QA/QC technicians, engineers, project managers, regulatory agents etc. who are supposed to be reviewing this data?
    • Scope: “This standard practice does not address closed loop control technology leading to device feedback and automatic adjustment of the three mentioned hot wedge variables.”
  6. This is a biggie! Similar to what is stated within this portion of the guidance document, my understanding of a “closed loop control system” is that the system monitors the electrical current reaching the motor (speed control) and heating elements (heat control) and automatically adjusts them to keep them within the preset (by user/operator) tolerances thus keeping the machine operating fairly uniformly along the entire length of the seam.  User interface thus allows the speed and heat welding parameters to be set and maintained by the machine through constant monitoring.
  7. However, if we are leaving these types of machines out of the “practice”, what are we supposed to do for them? Is a separate “standard” coming out?  And, wouldn’t these types of machines solve the issue presented in Section 4 of the standard (discussed later).
    • Scope: “This practice is field oriented focused on both construction quality control (CQC) personnel performing the actual welding and construction quality assurance (CQA) personnel inspecting the final seam product.”
  8. If the practice is field oriented for CQA, is the practice a part of the permitted plans and/or specifications? Is this practice something that will be included in bidding packages?
  9. CQA technicians need to be inspecting much more than just the final seam product. Especially if the QA is to be evaluating the acquired data from the welding machines.
  10. How and when would a QA know if the welder made changes, if the changes were good or bad, and how would they know the seam quality outside of the standard non-destructive/destructive testing currently used.

2.2 Reference: GM6 Practice for Pressurized Air Channel Test for Dual Seamed Geomembranes.

  1. One of the issues with this reference is that it is difficult to obtain – my understanding is that it is for GRI members only.
  2. It is also my understanding that GM6 differs somewhat from ASTM D5820, so in that case, which standard applies?
    1. My suggestion is that if any guidance within this document follows GM6, then a note should be made to allow the reader to know that the presented data comes from GM6; if not, remove GM6 from the list of reference documents.

2.2-3 Data Acquisition Welding Devices: “A hot wedge (or hot air) welding device equipped with data acquisition which then transfers wedge temperature, speed and pressure to a smart phone, tablet or computer so as to automatically adjust the welding device to the original or other designated values.”

  1. There should be data monitoring and recording requirements for the devices. By “monitoring”, I am referring to the interval at which data is coming into the machine where variances will alarm.  For “recording”, I am referring to how often that data is transferred from the machine to the data logger.  Both of these are extremely important.
    1. At what interval is the data monitored? It seems that there should be a requirement for continuous monitoring, regardless of what interval the data logger is recording at, so that alarms happen in real-time.
      1. How is the data monitoring interval actually confirmed? It would seem that there would be a required calibration for this.
      2. Assuming a calibration confirmation of continuous monitoring is required, how often is this calibration required?
    2. At what interval is the data recorded – every foot, every five feet, fifty-feet? The larger the interval, the more chance that unseen fluctuations could occur and go unnoticed, limiting the usefulness of the data.
      1. Again, it would seem prudent that a calibration is in order to ensure the recording interval is accurate, otherwise “anomalies” in the data won’t correspond to the same location on that seam when measured in the field and people may blindly repair the wrong location!
    3. What happens to the data that is supplied, and how is it interpreted? Where is the education on interpreting the data, from both an installer standpoint as well as CQA?  This is critical to avoiding kneejerk reactions among the different parties!
      1. Assuming that an anomaly is found, how is it handled? What is the guidance on what defines an anomaly as well as what follow-up is needed?  As mentioned above, first and foremost after a defined anomaly is seen in the data, confirmation needs to happen in the field to find the exact location, and by confirm, there needs to be a definition of how to confirm this.  Simply wheeling off “x” feet and doing a repair is not good enough!  Measuring wheels vary in distance, distance will vary based on the presence of wrinkles, and distance will vary based on true travel distance vs recorded travel distance if there is no calibration standard (if you don’t believe me, put some oversized tires on your vehicle and check the distance between mile-markers on a freeway – my Bronco II was off nearly 0.1 mile per mile!)
    4. There is no mention that other commonly recorded data still needs to be obtained and recorded in addition to that provided by the logger on the machine – sheet temperature, ambient temperature, weather conditions, material interface type for each weld, operator identification and machine number.
    5. Do the machines provide a way to see the data in real-time? And if so, how? If real time data transfer to a handheld device is required for utilization of the bubble and this practice what happens when real-time data is unavailable?  Is there a fall back protocol that is to be put into practice?  Installation cannot be stopped due to technical difficulties in data acquisition.

3.2.5 The Bubble: “The bubble or the window is defined by the geomembrane installer for the specific material, the specific welding machine and the site-specific conditions. Trial seams are tested to prove/confirm these details and are under the CQA inspector’s control.”

  1. A window or “bubble” is presented where the combination of proper heat, speed, and pressure result in a sound weld. Who really should develop this window?
  2. If installers are responsible for establishing the bubble, will they bid jobs with this practice? What kinds of liability are added to the installer if they set welding parameters? Will this cause warranty issues outside the current scope of warranty practices?
  3. Refer to comments on 1.2. In addition to these comments, I do not believe trial seams are the proper confirmation of whether these conditions are being met.  This is something that should be determined by the Manufacturer and/or Engineer in my opinion, or if not them, additional laboratory testing that goes beyond peel and shear and determines if the material has been overheated and excessively degraded (which may ultimately lead to long-term failure).
  4. Will a regulator be comfortable signing off on a material specific, site specific and machine specific bubble created by an installer with unknown background and unknown experience level?
  5. How far in advance is this bubble created?
  6. What if there are multiple types of welding machines on site? What if equipment needs to be changed out or repaired, is the bubble recreated, reapproved?  How does site testing change?
  7. Does this bubble take into account the fact that different machines slow their speed at different rates when they are working up slope? And what if there are multiple slope factors on a single site – is there a bubble for each grade?
  8. Does Ambient temperate effect the bubble? What about sheet temperature?  Does cloud cover combined with temperature effect the bubble?
  9. Where is the basis for creating a standardized formula that will work for all sites? There should be a baseline for bubble creators to start with to help ensure that their bubble is going to be accurate.
  10. What happens if a bad bubble is created? How is that determined?  How is the situation rectified if a bad bubble is determined mid-project?  Who is responsible for the cost of welding under a bad bubble?
  11. Regarding trial welds, what protocols are required for QA/QC personnel to review/confirm. For instance, if the trial weld is 10 feet long, should the QA be inspecting the data for that whole 10-foot length and selecting samples for trial seam testing based on those results?

There are a lot of questions and realistically any new practice will generate questions.  Some questions certainly need to be addressed before a standardized practice is finalized and some will be worked out over time should the practice be implemented by the industry.  A good CQA Plan will need to adopt and address a good portion of these questions.  But given the serious implications of the work we do as an industry and potential financial ramifications, we need to thoroughly examine this practice in detail before we can accept it as an industry.  There are simply way too many unknowns for practice adoption.  Part 2 of this blog will discuss the second half of the GRI-GM32 Standardized Practice: Practice thru Procedures.

Leave a Reply