... layer. Trial: Trial in dry places and buried in the concrete pipe, such as decoration ceiling, fire, lighting, instrumentation, engineering of ... . 2. double corrosion. Long service life. 3. Inner layer of insulation, safe and reliable. 4. Seismic shielding effect. 5 ... basic accessory tube. 2. Flame retardant anti-corrosion insulation layer non-toxic, harmless, environmental protection and so on. ...