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Protecting pipelines from corrosion under insulation

World Pipelines,

Corrosion under insulation (CUI) consumes a significant percentage of petrochemical industry maintenance budgets. Most of this money is spent on expensive items such as external piping inspection, insulation removal and reinstallation, painting and pipe replacements.

Coating with thermal sprayed aluminium (TSA) is one method that a number of operators in the petrochemical industry have adopted in the prevention of corrosion under insulation in pipeline systems.

Case study

One of Metallisation’s customers has an ongoing programme for applying TSA at a petrochemical plant.

The contractor on this specific jobsite is using two Metallisation MK73 flamespray systems in different spray locations. Blasting and inspection is completed in the morning lasting approximately four hours. TSA is applied in the early afternoon for approximately three hours and the final sealant application at the end of the day.

During the application of the TSA the operators checked the coating thickness periodically using a DFT gauge and made appropriate corrections along the way. The QA/QC inspector for the project also checked and recorded the coating thickness throughout the process. TO support the OA/QC process the spray operators produced witness plates on a daily basis, which were then tested for adhesion to ensure that it met the minimum 1000 psi – 6.9PMa coating thickness. Audit bond strength testing was also carried out periodically on the actual sprayed pipe sections.

Advantages of Metallisation MK73 flamespray

An advantage of the Metallisation equipment and process is the flexibility and long supplies, which provide a safe working environment and ease of use for operators. The sprayer and wireman can move freely around the worksite in the most efficient manner to suit the specific area.

The MK73 is perfect for difficult to access areas commonly found at petrochemical sites and has been designed specifically for this application area. It comes in three lengths, 150 mm, 300 mm, and 450 mm. The extension unit can spray directly forward or at a deflected angle up to 90° by varying the deflector air pressure. The deflection nozzle can also be rotated through 180° to allow spraying in a 360° arc around the pistol. The long supplies system provides flexible working conditions, particularly useful when spraying the underside of pipes.

Adapted from a press release by Emma McAleavey.

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