Now PC plastic guardrail tube waterproof is mainly sealed waterproof, the manufacturers surprise, sealing methods emerge in endlessly, factory after the test of flooding, but the use of water is still continuous, and even cracked pipe. To know after installation of guardrail tube always affected by temperature changes, tube pressure changing with temperature, high temperature expansion pipe shell, the cold extruded tube shell, wire entrance and end cover sealing glue with physical deformation, in the long run will appear crack, again meet temperature gas leakage, inspiratory when cooling, this time the moisture in the outside tube attached to swoop in. Typical process of water inlet: temperature change -- air pressure generation -- extruding outer tube -- seal failure -- negative air pressure water absorption temperature influence in addition to temperature change, solar radiation heating, greenhouse effect warming, internal circuit work heat, when the guardrail tube seal waterproof do well enough, if the tube does not leak, crack pipe will be increased accordingly; North has -25 degrees of low temperature, summer sunshine plus greenhouse effect guardrail tube has more than 60 degrees of high temperature, conventional sealing structure guardrail tube from temperature -25 degrees to +65 degrees will change 0.3 atmospheric pressure, the tube is not cracked can only be leakage, water is sooner or later. The traditional way to strengthen the sealing and waterproof, from the above analysis can be seen to be palliative, can be said to have entered a dead end.