Dalam era modern, listrik menjadi komponen krusial bagi berbagai aktivitas manusia. Pembangkit Listrik Tenaga Gas Uap (PLTGU) merupakan salah satu solusi efisien dengan memanfaatkan perpaduan turbin gas dan uap. Namun, efektivitas sistem pendinginan tertutup Closed Cooling Water (CCW) pada PLTGU Priok sering kali terhambat oleh fouling dan penurunan kinerja akibat akumulasi kotoran pada heat exchanger. Penelitian ini dilakukan dengan menggunakan metode pengumpulan data berupa pengamatan langsung, wawancara, serta studi literatur. Analisis data dilakukan secara kuantitatif untuk membandingkan efektivitas sistem Closed Cooling Water (CCW) sebelum dan sesudah pemeliharaan di PLTGU Priok Blok 1. Penelitian ini bertujuan menganalisis perbandingan efektivitas CCW sebelum dan sesudah perawatan. Hasil penelitian menunjukkan peningkatan efektivitas dari 38,32% sebelum perawatan menjadi 46,29% setelah perawatan, meskipun masih di bawah angka commissioning sebesar 53,75%. Perawatan yang dilakukan terbukti efektif dalam meningkatkan kinerja sistem, namun perbaikan lebih lanjut masih diperlukan. Faktor utama yang mempengaruhi efektivitas meliputi fouling dan LMTD (Log Mean Temperature Difference). Saran yang diberikan mencakup pentingnya pemeliharaan rutin dan penggunaan bahan berkualitas untuk meningkatkan performa CCW.

In the modern era, electricity has become a crucial component of various human activities. A Gas and Steam Power Plant (PLTGU) is one efficient solution that leverages the combination of gas and steam turbines. However, the effectiveness of the Closed Cooling Water (CCW) system at the Priok PLTGU is often hindered by fouling and performance degradation due to the accumulation of dirt in the heat exchanger. This research was conducted using data collection methods such as direct observation, interviews, and literature studies. Data analysis was performed quantitatively to compare the effectiveness of the Closed Cooling Water (CCW) system before and after maintenance at the Priok PLTGU Block 1. The research aims to analyze the comparison of CCW effectiveness before and after maintenance. The results showed an increase in effectiveness from 38.32% before maintenance to 46.29% after maintenance, although still below the commissioning figure of 53.75%. The maintenance carried out proved effective in improving the system's performance, but further improvements are still needed. The main factors affecting effectiveness include fouling and LMTD (Log Mean Temperature Difference). The suggestions provided emphasize the importance of routine maintenance and the use of high-quality materials to enhance CCW performance.