地下輸氣管線之破損原因調查及改善

Inspections and Improvements of Underground Gas Pipeline

新竹地區一條12吋天然氣管線，發生瓦斯洩漏造成很大的損失。管線開挖後發現一處如拇指大小，表面平滑光亮的蝕孔。本管線雖然有防蝕包覆及陰極防蝕保護，但仍發生管線腐蝕洩漏；因此確定目前的管線安全維護上仍有一些盲點。因此業主委託進行破損原因調查，並針對本管線進行全面的管線緊密電位量測及防蝕系統分析，以找出其他可能腐蝕區域及迷失電流干擾區進行維修。本研究報告主要分成三部份：第一部份破損原因分析：經分析結果確定管線遭電蝕干擾。第二部份防蝕現況調查：發現原有防蝕系統有些缺失，並且有幾處雜散電流干擾。第三部份為改善規劃及改善前後比較：依據調查結果提出對策進行改善，改善後防蝕效果明顯提昇。

Leakage occurred from a 12-inch gas pipeline in Hsinchu Region. A thumb size of localized corrosion was found after inspections. The outlook of the corrosion position is smooth and shining. According to original designs, the pipeline has coating wrap and cathodic protection system. However, leakage from corrosion still took place. Hence, some blind spots or unknown reasons exist during maintenance stage. To understand the damaged reasons, close internal survey, coating wrap inspections, and cathodic protection system evaluation were performed to investigate stray current interference. The present paper includes ( 1 ) analyses of damaged reasons, ( 2 ) improvements of anti-corrosion system, and ( 3 ) a comparison before and after improvements.