TPO and PVC Welding Guidelines
July 22, 2019
Cold welds are a major concern for any thermoplastic roofing installer. But following a few basic guidelines can go a long way toward ensuring good, long-lasting welds on TPO, PVC, and KEE HP membranes. In this post, we’ll discuss a few best practices that reduce the chances of cold welds and help ensure the watertight integrity of TPO, PVC, and KEE HP single-ply roof systems.

1. Appropriate Equipment
Use proper power sources or commercial-grade generators. Generators should be rated for 3,000 watts for two hand welders, or 6,500 watts for one auto-welder. Proper extension cords are critical. For auto-welders, use a 10-gauge wire with a maximum length of 100 feet; for hand welders, use a 12-gauge wire with a maximum length of 100 feet. Welders should be in good shape, with clean air screens and a clean nozzle.

2. Proper Temperatures
The following are starting guidelines for temperature, speed, and airflow. Settings may vary depending on membrane thickness (45-, 50-, 60-, or 80-mil).

Leister Varimat
Temp
Speed
Airflow
TPO
1004°F
12.5 ft/min
100%
PVC & KEE HP
1094°F
8.5 ft/min
100%

Leister V2   Temp  Speed Airflow
TPO
986°F 18 ft/min 90%
PVC & KEE HP
1094°F 10.4 ft/min 75%

BAK LarOn Temp Speed  Airflow 
TPO
1004°F 12.5 ft/min 100%
PVC & KEE HP 1094°F 8.5 ft/min 100%

3. Critical Welding Steps

Keep in mind that ambient temperatures will affect welding temperatures and speeds, as will welding in the sun versus welding in the shade. Certain substrates can hold heat in the membrane (polyiso insulation), while others can rob the heat from the membrane (concrete). When hand welding, immediately roll across the hot seam at a 45° angle with a 2” silicone roller. This helps to ensure the top membrane is adequately pressed into the bottom membrane. When welding across a step-off, be sure to crease the top membrane into the step-off with a 2” silicone roller immediately after welding. This will help prevent a water channel from forming in the weld. It’s important to perform test welds several times each day because of changing ambient and membrane temperatures. Simply cut a 1”-wide strip across the weld and peel to inspect the weld area. Remember to probe all seams at the end of each work day.

4. Cleaning and Maintenance

Always clean aged or dirty membrane before welding. On PVC or KEE HP, use PVC and KEE HP Membrane Cleaner; on TPO, use Weathered Membrane Cleaner. Clean all residue from the weld area and allow it to dry before welding. Maintain your equipment before, during, and after welding. Regularly inspect the silicone pressure wheels on your auto-welder and hand roller to make sure they’re not affecting the integrity of the membrane while welding or rolling. Clean the char off the heat gun nozzle using a brass wire brush and keep the intake free of debris to allow maximum airflow. On the auto-welder, adjust the nozzle to eliminate heel drag.
Following these helpful hints will ensure a better installation with fewer cold welds. If you have questions, check out Versico’s TPO and PVC Welding Guides or contact your Field Service Representative.

TPO Welding Guide
PVC Welding Guide 



    John Greko
    PVC Product Manager
    Product Marketing
    john.greko@carlisleccm.com

December 5, 2019
Seam Probing

Seam probing is an important final step in the hot air welding process because it is a good indicator to determine if proper fusion has occurred between the membrane layers. Whether the membrane is TPO or PVC, both products need to be probed – but with slightly different techniques. Probing must be done once hot air welds have thoroughly cooled (at least 20 minutes). Premature probing can damage warm seams. Hot air welded seams must be probed throughout the day to check seam quality and to make proper adjustments to hot air welding equipment. The repair of deficiencies must be done routinely throughout the day, but no later than the end of each workday. A blunt or dull cotter pin puller is an acceptable tool to perform the probing task. Versico offers a custom-designed Seam Probe that incorporates an ergonomic, threaded handle with a heat-treated, plated steel tip. With continued use these tools will wear down, creating a tip that is too sharp for probing. Blunting the tip is necessary when this occurs. When a substantial amount of probing is necessary, an extension pole can be threaded into the handle of the Versico probe. This allows the operator to stand up while probing long runs of field seams. Getting started Draw your probing tool tip along the edge of the heat welded seam. Apply firm pressure to probe the seam junction, but not into the bottom membrane sheet. The tool will not penetrate into the lap area of a properly welded seam. If the seam probing tool penetrates into the welded overlap area, use a water-soluble marker to mark the beginning and the end of voids or wrinkles in the seam edge. Repair seam deficiencies as soon as possible using the hand held welder. Versico recommends that repairs be made the same day deficiencies are discovered. Probe repaired seams after they have cooled completely. If the repair is acceptable, wipe off the water-soluble marker lines; if not acceptable, repair the seam using standard heat welded overlay procedures. Another reason all laps must be probed each day soon after they have cooled is to verify the welder set-up is effective. Particular attention must be given to all membrane intersections and heat welded seams at insulation joints. In addition, there should be periodic checks (including at the start of each day) to verify good peel strength. Considerations when probing TPO systems 1.) TPO does not "flow" like PVC. If you observe an area in which you see "flow" of the bottom ply, scorched areas of detail/flashing membrane, or scorched field membrane welds, these areas should be probed. If these areas are overheated to the point of membrane damage, an overlay repair will be required even if the weld probes successfully. 2.) A properly heated field membrane weld will typically have a visual "sheen" approximately 1/2" wide on the bottom sheet at the weld overlap. When walking seams, look for the sheen. If it is not present, probe to ensure weld quality.  3.) TPO seams require a minimum 1.5" weld. Welds less than 1.5" must be overlaid as stated in Versico’s specifications and details, even if probing does not produce deficiencies. Considerations when probing PVC systems 1.) Welds on PVC systems should produce "bleed out". Bleed out refers to the flow of the bottom ply (of the top sheet) outside of the weld. If you do not see bleed out at seam areas, this increases the probability the seam did not receive enough heat when it was welded. Be sure to probe these areas to ensure weld quality. 2.) PVC is a “softer” and more flexible membrane than TPO. As such, a different probe should be used than the one used on TPO roofing systems. The PVC probe should have a blunt/dull tip, or utilize a "hook" screwdriver with a flat head.  3.) PVC seams require a minimum 1.5" weld. If you observe welds which are less than 1.5", these should be overlaid following specifications and details, even if probing does not produce deficiencies. Remember, application of Cut Edge Sealant should not begin until all probing is completed. Please contact Jim Gage with questions.     Jim Gage     Senior Technical Specialist     Product Marketing     james.gage@carlisleccm.com

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November 21, 2019
Benefits of Using White P&S EPDM Accessories on TPO Systems

Versico Roofing Systems allows contractors to use several of its productivity-boosting VersiGard® EPDM Peel & Stick accessories on VersiWeld® TPO roofing systems with up to 20-year Total System Warranties. VersiGard White EPDM Peel & Stick (P&S) accessories can provide substantial labor savings on projects with hard-to-flash penetrations and are ideal when using a generator and hand welder isn't practical. Regardless of which roof system is being installed, experienced roofers understand there is always a good chance of encountering hard-to-flash roof penetrations, or simply a high volume of penetrations. Determining the best way to flash these items in a productive manner while ensuring a long-term watertight seal can be a serious challenge. This is where VersiGard White P&S accessories come into play. Keep in mind your alternative EPDM flashing options for TPO systems: Run into a hard-to-flash penetration? VersiGard White P&S Uncured Flashing is an option to consider. This material is highly malleable and adapts easily to odd shapes and surfaces, making it ideal for flashing pipes, scuppers, and other irregularly shaped penetrations. Overwhelmed by hundreds of roof curbs? Boost productivity by flashing curbs with VersiGard 20" White P&S Cured Flashing in conjunction with VersiGard White P&S 7" x 9" Inside/Outside Corners. This is the fastest way to flash roof curbs and can reduce application time by up to 70% when compared to non-P&S flashing options. White EPDM P&S accessories are also a great option for repairs on TPO roofs when access to power is difficult or it isn't practical to use a generator and hand welder. Transporting generators, power cords, and welders to difficult-to-reach roof sections can be cumbersome and labor-intensive. This additional labor can be avoided by white EPDM P&S accessories, since most of these materials will fit snugly into a backpack! If you're interested in receiving a free trial of VersiGard White EPDM Peel & Stick accessories, please submit a request using this form. Approved Products: VersiGard White EPDM P&S Pipe Seals VersiGard White EPDM P&S Pourable Sealer Pockets VersiGard White EPDM P&S Inside/Outside Corners and T-Joint Covers VersiGard White EPDM P&S T-Joint Covers VersiGard White EPDM P&S Uncured Flashing VersiGard White EPDM P&S 20" Cured Flashing     Ryan Ferguson     EPDM Product Specialist     Product Marketing     ryan.ferguson@carlisleccm.com

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October 10, 2019
Special Color TPO Accessories

As the demand for different colored roof membranes has grown, Versico introduced its TPO Color Palette with five new colors. In addition to standard white, gray, and tan, Versico’s TPO Color Palette now features Rock Brown, Slate Gray, Terra Cotta, Patina Green, and Medium Bronze. Projects that use special color membrane from the TPO Color Palette usually need flashings and accessories in the same color. Here, contractors have two choices, one of which is painting standard accessories to match the membrane. However, this is a great opportunity to use Versico’s custom TPO accessory program and avoid painting altogether. All of Versico’s custom accessories are available in the five TPO Color Palette colors, as well as white, tan, and gray. Whether it’s a simple split pipe seal or a complex prefabricated curb wrap, Versico can make it in all eight TPO colors and get it to the job quickly. In addition to being available in eight colors, here are some other great advantages to using custom flashings from Versico: • Save time vs. field fabrication: Trying to field-fabricate flashings can be time-consuming work, even for the most skilled and experienced roofers. Using prefabricated flashings saves time. • No need for paint: There’s no need to prime and paint the accessories to match the membrane; just install and go. • Speed: Custom accessories can be fabricated and shipped within days, not weeks. • Quality: All of Versico’s custom TPO accessories carry the Certified Fabricated Accessory (CFA) stamp of approval, indicating they are eligible for coverage as part of Versico’s Total System Warranty. Next time you have a project using Versico’s TPO Color Palette TPO, consider using custom accessories to make the job faster and easier to install. VersiWeld TPO Special Color Painting Guide  VersiWeld TPO Special Color Program Custom Accessory Quote Request Form      Adam Burzynski     TPO Product Manager     Product Marketing     adam.burzynski@carlisleccm.com

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