... 2.Anti-freezen & pressurized 3.10 years warranty Solar thermal vacuum tube solar collecotr a. Module design, arbitrary combination, harmonize ... red copper flow passage6) Glass tube: new trivalent element heat tube, borrosilicate glass 3.37) Solar working station8) With heat pipe: ... ,4Mpa,welding pressure 4MpaDust Ring GasketSilicon Rubber Vacuum Tubetri-element tube,High boron and silicon content 3.3, ...