MAINTENANCE OF DOCK STEEL PILES
System for fixing HDPE jackets using plastic bolts.
The coatings most commonly used as corrosion protection systems in the splash and submerged zone of new carbon steel piles are epoxies When these coatings reach their service life, the piles must be subject to maintenance work. The most recommended coatings for this work are petrolatum tapes and HDPE liners. In practice, the preparation of surfaces that is commonly carried out in these cases is cleaning of marine life attached to the pile and a touch up in specific areas that show localized faults of paint or visible corrosion, keeping much of the original coating.
The main restriction of the petrolatum tape is the low adhesion to aged epoxy paints. On the contrary, on bare steel the adhesion of this tape is quite good, so the optimal protection and service life of the new coating will be achieved by completely removing the original paint. A great part of the coatings based on petrolatum tapes use stainless steel bands as an attachment system of the HDPE liners. They undergo premature and accelerated corrosion in the Chilean coast and are damaged and cut at an early stage, so they must be periodically replaced. The solution to this problem was achieved by including a design based on bolted joints, with high resistant plastic bolts, as a system to fix the HDPE liners. In addition to these bolted joints, the new design considers a rib that provides rigidity to the system in the area of longitudinal overlap of the liner, which reduces the potential bents between bolts and reduces the entry of marine flora and fauna to the interior of the coating.
To determine the optimum maintenance system to ensure a long service life of the piles, it is necessary to previously perform a thorough diagnosis of the situation. This diagnosis includes the degree and type of corrosion of the pile, the condition of the painting and the detailed evaluation of the cathodic protection system. The information gathered from this diagnosis will be the basis of the project maintenance engineering. This engineering should consider at least the following: design of technical solutions; products to be used; workplan; surface treatment; treatment of pittings and complex sectors; inspection plan; and the maintenance procedure of the new anticorrosive system, including coating and cathodic protection. As the variables to be assessed, in terms of the corrosion level, the state of the protection systems and the repair procedure for each dock are different, the diagnosis and survey to be performed is specific to each facility, where the result obtained from a dock should not be considered as the basis for another.
Coating based on petrolatum tapes for pile maintenance.