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Polywater Customer Service recently fielded a call about FST Foam Duct Sealant from a Distribution Linemen Superintendent at a large eastern utility. The inquiry included this most excellent question: "Hello, I have a question regarding use of the product on the top of a riser conduit on a pole. I see the use of the two foam wraps with the first wrap being pushed 5" into the conduit for a horizontal installation. Do you recommend the same installation method for vertically mounted riser conduits attached to poles; that is, a foam wrap, a void followed by a second foam wrap with sealant inserted in between? Or, on a vertical conduit, can we do one foam wrap followed by the sealant material alone, without the second foam wrap? All photos I see illustrate a horizontal conduit, none vertically. Thanks." If you picture the clear sample seal shown at left standing on its end, simulating a vertical conduit, you can visualize his question. Is the top damming wrap required, since gravity would tend to keep the expanding FST foam from going too far? The answer is, yes, the second foam damming wrap is required even in vertical installations. The presence of the top wrap restricts the foam expansion, creating critical compression that forces the foam laterally against the duct walls, increasing adhesion. This improves water and gas blocking and pull-out strength. The top damming wrap is needed for an optimal seal. Note that this recommendation applies equally to SolidSeal Duct Plug for communications conduits. Be ready for this question from the field. |
