Analisis Peletakan dan Kebutuhan Proteksi Katodik Pada Mooring Buoy di Pertamina Fuel Terminal Luwuk

Korosi adalah salah satu penyebab kerusakan yang umum terjadi pada mooring buoy akibat adanya oksidasi pada permukaan pelat baja. Tujuan dari penelitian ini adalah untuk mengetahui kebutuhan dan peletakan proteksi katodik serta biaya yang dibutuhkan dalam pengadaan proteksi katodik pada mooring buoy dengan menggunakan aturan BKI (Biro Klasifikasi Indonesia) dan DNV (Det Norske Veritas Industry Norway). Dalam sistem proteksi katodik terdapat dua metode proteksi katodik yaitu Sacrificial Anode Cathodic Protection (Anoda Korban) dan Impressed Current Cathodic Protection (ICCP). Pada penelitian ini digunakan metode anoda korban karena instalasi lebih sederhana sehingga tidak memerlukan keahlian khusus dan penghubung anoda telah terlindungi secara katodik. Mooring buoy dengan tinggi 2,380 m, berdiameter 3,200 meter dengan umur desain proteksi katodik yaitu 5 tahun. Anoda yang digunakan pada penelitian ini adalah anoda dengan tipe Longated flush-mounted Z9.0H1 (Welded Type) dengan dimensi 355 x 85 x 45 mm. Dari hasil penelitian ini didapatkan total massa anoda yang dibutuhkan untuk memproteksi mooring buoy adalah 48 kg dengan jarak pemasangan antar anoda pada pelat lambung topside adalah 2,000 m dan pada pelat bottom swim lambung adalah 3,000 m serta estimasi biaya yang dibutuhkan dalam pengadaan proteksi katodik mooring buoy adalah Rp. 7.487.075.

Cathodic Protection Design Consideration for an Offshore Flexible Riser Connected to an Impressed Current System

Flexible risers are regularly used to produce oil and gas in subsea production systems and by nature interconnect the subsea production system to the floating or fixed host facilities. Unbonded flexible pipes are made of a combination of metallic and non-metallic layers, each layer being individually terminated at each extremity by complex end fittings. Mostly submerged in seawater, the metallic parts require careful material selection and cathodic protection (CP) to survive the expected service life. Design engineers must determine whether the flexible pipe risers should be electrically connected to the host in order to receive cathodic protection current or be electrically isolated. If the host structure is equipped with a sacrificial anode system, then electrical continuity between the riser and the host structure is generally preferred. The exception is often when the riser and host structure are operated by separate organizations, in which case electrical isolation may be preferred simply to provide delineation of ownership between the two CP systems. The paper discusses these interface issues between hull and subsea where the hull is equipped with an impressed current cathodic protection (ICCP) system, and provides guidance for addressing them during flexible pipe CP design, operation, and monitoring. Specifically, CP design philosophies for flexible risers will be addressed with respect to manufacturing, installation and interface with the host structure’s Impressed Current Cathodic Protection (ICCP) system. The discussion will emphasize the importance of early coordination between the host structure ICCP system designers and the subsea SACP system designers, and will include recommendations for CP system computer modeling, CP system design operation and CP system monitoring. One of the challenges is to understand what to consider for the exposed surfaces in the flexible pipes and its multiple layers, and also the evaluation of the linear resistance of each riser segment. The linear resistance of the riser is a major determinant with respect to potential attenuation, which in turn largely determines the extent of current drain between the subsea sacrificial anode system and the hull ICCP system. To model the flexible riser CP system behavior for self-protection, linear resistance may be maximized, however the use of a realistic linear resistance is recommended for evaluation of the interaction between the host structure and subsea system. Realistic flexible linear resistance would also reduce conservatism in the CP design, potentially save time during the offshore campaign by reducing anode quantities, and also providing correct evaluation of drain current and stray currents.