Perencanaan Support Tower Pada Stack Reformer Unit 100 (010-S01) di Site Plant PT. Kaltim Methanol Industri Bontang

Fikri Dzakaria, Dr. Eng. Ir. Sito Ismanti, S.T., M. Eng., IPM.

2023 | Skripsi | TEKNIK SIPIL

Salah satu utilitas keluaran gas emisi pada pabrik PT. Kaltim Methanol Industri adalah stack reformer yang terletak di unit 100. Dalam upaya memastikan PT Kaltim Methanol Industri telah menekan emisi dan mendukung target Net Zero Emission pada tahun 2060, evaluasi terhadap keluaran sumber emisi yaitu stack reformer unit 100 harus dilakukan berkala. Walaupun demikian, bangunan pendukung untuk pengambilan sampel yang dilakukan pada ketinggian ± 30 meter di outlet stack reformer belum tersedia. Dinding stack reformer yang relatif tipis membuat perencanaan tangga monyet yang menempel pada dinding dinilai tidak cocok berdasarkan PT. Kaltim Methanol Industri. Oleh karena itu, perancanaan support tower sebagai sarana untuk pengambilan sampel sebagai alternatif harus dilakukan.

 

Desain awal struktur support tower dirancang dengan tipe special concentrically braced frame (SCBF) dengan bentuk geometri V terbalik (Inverted V-Bracing). Dimensi bersih menara memiliki tinggi 28,5 meter dan memiliki 7 lantai dengan lantai 2-7 memiliki bentang per-lantainya 4 meter dan lantai 1 memiliki bentang ke lantai berikutnya sebesar 4,5 meter. Desain awal fondasi support tower dirancang menggunakan tipe fondasi telapak (Isolated footing) dengan dimensi 2 x 2 x 0,6 meter yang dipasang di dasar masing-masing kolomnya. Analisis struktur atas dan fondasi masing-masing menggunakan aplikasi SAP2000 dan GS AFES 3.0. Rencana pembebanan dan parameter-parameter perancangan direncanakan berdasarkan panduan Requistion for engineering, procurement & construction stack (010-S01) platform dari PT. Kaltim Methanol Industri. Metode perancangan dilakukan dengan memastikan keamanan struktur atas terlebih dahulu kemudian dilanjutkan dengan perancangan fondasi. Keamanan struktur atas ditinjau  berdasarkan ketahanan terhadap pembebanan gempa dan kekuatn per-elemen-elemen struktur support tower. Keamanan fondasi ditinjau berdasarkan kapasitas dukung tanah, stabilitas (guling dan geser) dan kekuatan (penulangan fondasi). Acuan yang digunakan dalam perancangan berdasarkan SNI, Petros Oil-Gas Training (Desain struktur daerah kilang minyak), dan ACI 318. Setelah perencanaan struktur atas maupun fondasi telah memenuhi tingkat keamanan, juga dilakukan komparasi penggalian pemasangan fondasi dengan kedalaman alternatif 1 meter untuk mendapatkan gambaran efisiensi pekerjaan konstruksi.

 

Berdasarkan hasil perencanaan struktur atas dengan desain awal menggunakan profil kolom H 200 x 200 x 8 x 12, profil balok C 200 x 80 x 7,5 x 11 dan profil bresing C 150 x 75 x 6,5 x 10 tergolong aman terhadap beban gempa (Mode shape, periode struktur, metode kombinasi ragam, partisipasi mass, gaya geser dasar seismik dan simpangan antar tingkat) dan kekuatan per masing-masing elemen memiliki demand per capacity ratio kurang dari 1. Berdasarkan hasil perencanaan fondasi desain awal tergolong aman terhadap kapasitas dukung, nilai aman terhadap guling dan geser (lebih besar dari 2 untuk guling dan 1,5 untuk geser). kedalaman fondasi kedalaman 1 meter dapat memangkas Rp.1.1200.000 berdasarkan harga pekerjaan galian studi kasus tower crane. Harga pekerjaan galian studi kasus tower crane lebih murah dibanding harga Kota Samarinda 2017.

One of the emission-generating utilities at PT Kaltim Methanol Industri's plant is the stack reformer located in unit 100. In an effort to ensure that PT Kaltim Methanol Industri has reduced emissions and supports the Net Zero Emission target by 2060, evaluation of the output of the emission source, the stack reformer unit 100, must be carried out periodically. However, there is no supporting building for sampling at a height of ± 30 meters at the outlet of the reformer stack. The relatively thin wall of the stack reformer makes the planning of a monkey ladder attached to the wall unsuitable. Therefore, the design of the support tower as a means for sampling as an alternative must be done.

 

The initial design of the support tower structure was designed with a special concentrically braced frame (SCBF) type with an inverted V-bracing geometry. The net dimension of the tower is 28.5 meters high and has 7 floors with floors 2-7 having a per-floor span of 4 meters and floor 1 having a span to the next floor of 4,5 meters. The initial design of the support tower foundation is designed using a type of isolated footing with dimensions of 2 x 2 x 0,6 meters installed at the base of each column. The superstructure and foundation were analyzed using SAP2000 and GS AFES 3.0 applications, respectively. The loading plan and design parameters were planned based on the Requistion for engineering, procurement & construction stack (010-S01) of PT Kaltim Methanol Industri platform. The design method is carried out by ensuring the safety of the superstructure first and then proceeding with the foundation design. The safety of the superstructure is reviewed based on the resistance to earthquake loading and the strength of each element of the support tower structure. While the foundation safety is reviewed based on soil bearing capacity, stability (overturning and shearing) and strength (foundation reinforcement). The references used in the design are based on SNI, Petros Oil-Gas Training (Design of oil refinery area structures), and ACI 318. After the planning of the upper structure and foundation has met the safety level, a comparison of the excavation of the foundation installation with an alternative depth of 1 meter is also carried out to get an overview of the efficiency of construction work.

 

Based on the results of the upper structure planning with the initial design using column profiles H 200 x 200 x 8 x 12, beam profiles C 200 x 80 x 7,5 x 11 and bracing profiles C 150 x 75 x 6,5 x 10 classified as safe against earthquake loads (Mode shape, structural period, variety combination method, mass participation, seismic base shear force and deviation between levels) and strength per each element has a demand per capacity ratio of less than 1. Based on the results of the initial design foundation planning is classified as safe against bearing capacity, safe value against overturning and shear (greater than 2 for overturning and 1,5 for sliding). Foundation depth of 1 meter depth can cut Rp. 1.120.000,00 based on price of excavation work of the tower crane case study. The price of excavation work in the case study tower cranes is cheaper than the price of Samarinda City 2017.

 

Kata Kunci : support tower, special concentrically braced frame, fondasi telapak, Komparasi pekerjaan galian.