... warranty Solar thermal vacuum tube solar collecotr a. Module design, arbitrary combination, harmonize with the building perfectlyb. Intelligent control and ... ,Working pressure,4Mpa,welding pressure 4MpaDust Ring GasketSilicon Rubber Vacuum Tubetri-element tube,High boron and silicon content 3 ... ,Gradual change SS-AL-Nx/Cu selective absorption coating,Vacuum Degree,P<=5*10-4,Service Life,10 years ...