For such a short video, there were several things that I identified. I’ll post them in the order that I identified them.
- No rub sheet to set the extrusion welder on. It is fairly common practice anymore not to use rub sheets with the welding equipment – and rub sheets are often not even specified any more for small equipment/hand tools. Hence, avoidable damages still occur.
- Purging the extrudate from the extrusion gun. This needs to be done prior to resuming welding to remove the heat degraded extrudate from the barrel. However, I am not sure this purge was long enough to remove all the heat degraded extrudate. It seemed short to me. The extrusion rod should be fed such that the rod immediately above the feed is part of the purge to ensure the degraded material has been removed.
- Purged extrudate put on the welding machine. This is a good thing – it wasn’t thrown on the geomembrane which surprisingly still happens.
- Extrusion welding.
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- It appears the extrusion bead was applied without grinding which could be problematic since we don’t know how long the original extrusion weld had been sitting there. I commonly hear and/or see specifications requiring grinding to occur if the extrudate has cooled for 5 minutes, although I believe this requirement should be reduced based on environmental conditions.
- The operator runs the machine backwards which is problematic for several reasons: one, the Teflon shoe is shaped for forward progression; and two, the welding parameters of heat (no preheat) and pressure are changed.
I’ll try to get more definitive answers to #3 and #4a from the experts during the GEOTECHNICAL Frontiers panel discussion next week!
In these blog posts, Do You See What Glen Sees, I will present a photograph or short video related to earthwork or geosynthetics construction and have you identify the significance of what you’re seeing.
It could be things being done correctly or incorrectly. Primarily, these will be things that impact quality.
In addition to my blog, I’ll post this content on X and LinkedIn. You can post your response on one of those two.
I’ll give you my thoughts on each photo or video when I post the next installment.
Do you see what I see? Or did you find something I missed? I’m excited to find out!
