... prevent condensation, a vapor resistance layer must be added. However, valves and some other special parts are hard to be treated ... the pipes with special adhesive before installing the pipelines. For valves, elbows, tee-junctions, etc. that are in complex shapes, you ... -to-small sequence, i.e., elbows, tee-junctions, pipes, valves and flanges.The glue should be applied in proper amount, and the ...