Corrosion Mitigation of Hot Water Copper Pipes on Offshore Platforms and Possible Alternatives
Authors: Aoudi H. K. , Alabadi S. A. , Al-Shouly W. , Toubar A. , Al-Safetli K. , Saeed W. 
Published: November 2017

Although copper is principally resistant to waterside corrosion, conditions can change driving this noble metal to experience corrosion due to chemical composition of water that flows through it c. In some cases of corrosion, the deterioration process may be managed effectively and economically by a number of water treatment alternatives. This paper will explain how copper pipes were corroded at an existing offshore field, and propose ways to mitigate such failures on an offshore field in the future.

In one of the accommodation platforms for ADMA-OPCO, unwanted factors were discovered that led immune copper pipes to corrode heavily when used in water service. In order to predict the corrosivity of the transported potable water, a number of chemical and physical aspects where studied to determine whether potable water was a contributing factor in the corrosion of copper pipes. Potable water, from reverse osmosis on offshore field (a newly commissioned field), is heated in hot water heaters that are installed in the accommodation platform to around 60 °C prior to being distributed to various consumers via the piping network. After a period of one year, pinhole leaks were observed in various locations causing hazardous living conditions for site personnel. In order to investigate the cause of this incident, various lab tests were run to study the chemical composition of potable water before and after getting transported through the copper pipes at different times. Other factors were also studied; this includes the pH and temperature of the transported water.

Analytical report for potable water analysis was carried out measuring the electrical conductivity, such as pH and chloride content. In addition to that, a graphical correlation was represented to justify any relative corrosivity that may have initiated the corrosion process. On the contrary, all results showed that the quality of water being distributed was as per standard and is not related to the deterioration that took place in copper pipes. Finally, a sample of the copper pipe was cut and studied. It was observed that some chloride residues were found in the cut pipe. A thorough investigation was carried out on the quality of water used during the hydro test and that may explaine the reason of chloride residue existance in the pipes present. Therefore, it was tested again to find the chloride content in the sample water used for hydrotest was higher than standard which led to accumulation of chloride in the pipes which was then activated during transport of the tubes that led to the corrosion of highly water corrosion resistant copper pipes.

Since there is no universal water treatment to prevent all corrosion issues in potable waters, a new and more practical way to transport water for domestic use was suggested and currently a feasibility study is being conducted to study the effectiveness of substituting copper pipes with Chlorinated Polyvinyl Chloride (PVC) pipes on offshore platforms. Health aspects, durability and installation cost are being investigated along with the most vital feature which is its ability to operate at high temperatures internally and externally.