xii DAFTAR GAMBAR Gambar 2.1 Ketel pipa api....................................................................................10 Gambar 2.2 Ketel pipa air.....................................................................................11 Gambar 2.3 Kerangka pikir penelitian..................................................................28 Gambar 3.1 Pohon masalah...................................................................................37 Gambar 3.2 Pohon sasaran.....................................................................................40 Gambar 3.3 Pohon alternatif..................................................................................42 Gambar 3.4 Matriks kerja......................................................................................43 Gambar 4.1 Korosi water tube...............................................................................53 Gambar 4.2 Sight glass..........................................................................................55 Gambar 4.3 Doubling water tube...........................................................................66 Gambar 4.4 Siklus perawatan................................................................................67