Prevention Measures Against External Corrosion of Plants

Since Niigata plant of Mitsubishi Gas Chemical Company locates in a coast and many carbon steel pipes are used at there, our longtime challenge item is the External Corrosion (EC).

To prevent plants from being damaged by EC, we had tried to implement various EC countermeasures, but they required much resource. And it was not easy to eliminate all leakage caused by undetectable EC. So we needed to enhance effectiveness of those measures.

Based on EC trouble records, we established the new standard to inspect EC with three steps last year. 1^st step is a visual inspection by plant operators from the ground. 2^nd step is an investigation by plant staff and the inspection team. 3^rd step is a Non Destructive Inspection by external experts. These three steps are carried out every year. Application of the new standard provided decrease of the troubles by EC. This time, we focus on 1^st step visual inspection －especially, Corrosion Under Insulation（CUI）－and report it. Skin of pipes under insulation cannot be looked directly, so it is known that the efficient management is difficult.

Staff at a plant collected data about CUI through their voluntary activities. The activity led them to acquire the knowledge about CUI, and they noticed that CUI could be categorized into certain types, almost 24 items by locations where corrosion tend to become severe. They discussed this finding with staff of our maintenance section and construction company. After that, our EC inspection standard was revised with the new knowledge, and we started to use the standard for our qualified EC inspector education program. It is really useful to detect EC point before being damaged.

In addition to the described activity, we promote an evaluation of the better insulation construction method. We shall continue improvement activities “KAIZEN” in future.