PROSES

RANCANG BANGUN PROTOTYPE MESIN PENGERING JAGUNG SISTEM KONVEYOR KAPASITAS 32 KG/PROSES

LAPORAN TUGAS AKHIR Diajukan Untuk Memenuhi Sebagian Persyaratan Dalam Menyelesaikan Program Pendidikan Diploma III

SPESIALISASI MESIN PRODUKSI PROGRAM STUDI TEKNIK MESIN

Oleh: DANIEL DYONESIUS MALAU

NIM: 1005011026

MENARA HUTAGAOL

NIM: 1005011064

RONI MALAU

NIM: 1005011086

ROWILMAN SIHALOHO

NIM: 1005011088

SEPTIANSYAH

NIM: 1005011093

JURUSAN TEKNIK MESIN POLITEKNIK NEGERI MEDAN MEDAN 2013

INTISARI Para petani Indonesia umumnya masih menangani hasil panen pertaniannya dengan cara tradisional. Ciri utama dari cara tradisional ini adalah perlakuannya tergantung pada alam. Pengeringan hasil pertanian jagung merupakan salah satu bentuk penanganan setelah panen yang cukup banyak sehingga menarik perhatian kami sebagai perancang. Untuk mengatasi masalah ini kami merancang dan membuat prototype mesin pengering biji jagung dengan sistem konveyor. Prototype mesin pengering biji jagung sistem konveyor ini dapat menurunkan kadar air dari sekitar 19% menjadi 14% dengan lama pengeringan 2 jam dan ketebalan jagung 1cm. Mesin ini menggunakan motor ½ HP dan memiliki suhu maksimal 70oC. Dalam proses pengeringan ini udara panas yang dihasilkan oleh hot gun dihembuskan berlawanan arah dengan arah gerak biji jagung, dan kemudian keluarannya adalah biji jagung yang telah kering (kadar air 14%). Dari percobaan yang dilakukan, setelah dilakukan pengujian maka dapat disimpulkan bahwa mesin secara keseluruhan dapat bekerja secara efektif karena prototype mesin tersebut dapat mencapai kapasitas dan kadar air yang kami inginkan. Kata kunci: biji jagung, hot gun, pengering, kadar air.

ABSTRACT Indonesian farmers in generally still handle their harvest with the traditional system. The main characteristic of this traditional system is depends on nature. Drying corn crops is one of many form of treatment after harvest so that it can be attract our attention as planner. To solve this problem we make the prototype corn kernels drying machine with conveyor system. From our experiment this prototype corn kernels drying machine with conveyor system can be reduce the water content from around 19 % to 14% with drying time two hours and thickness 1 cm. This machine uses ½ HP motors and has a maximum temperature until 70oC. In this drying process, the hot air which generated by hot gun flows opposite direction to the moving of corn kernel as sample, and then the product is the dry corn kernels. Of experiment were carried out, after testing it can be concluded that the overall machine can achieve the capacity and water content what we want. Keywords: corn kernels, hot gun, dryer, water content.

DAFTAR ISI

SPESIFIKASI TUGAS AKHIR ...................................................................... ii LEMBAR PERSETUJUAN ............................................................................iii LEMBAR PENGESAHAN ............................................................................. iv INTISARI .......................................................................................................... v ABSTRACT ...................................................................................................... vi KATA PENGANTAR ..................................................................................... vii DAFTAR ISI ..................................................................................................... ix DAFTAR GAMBAR ...................................................................................... xvi DAFTAR TABEL ......................................................................................... xvii DAFTAR LAMPIRAN ................................................................................xviii

BAB I

PENDAHULUAN ............................................................................ 1 A. Latar Belakang ............................................................................ 1 B. Perumusan Masalah .................................................................... 2 C. Tujuan ......................................................................................... 2 D. Manfaat ....................................................................................... 3 E. Teknik Pengumpulan Data .......................................................... 3

BAB II

LANDASAN TEORI....................................................................... 4 A. Sejarah Jagung ............................................................................ 4 1. Kadar Air jagung ................................................................... 6 2. Kegunaan Tanaman Jagung .................................................. 6 3. Nilai Ekonomis Jagung Hasil Pengeringan ........................... 7 4. Pengelolaan Jagung Hasil Pengeringan ................................ 7 5. Standar Mutu Jagung ............................................................ 8 B. Pengeringan ................................................................................. 9 C. Proses Pengeringan ................................................................... 12 1. Pengeringan Thermal (Thermal Drying) ............................. 14 2. Pengeringan Osmosis (Osmosis Dehydration) ................... 14

3. Pengeringan Mekanik (Mechanical Dewatering)................ 14 D. Metode Perpindahan Panas ....................................................... 15 1. Konveksi ............................................................................. 15 2. Konduksi ............................................................................. 16 3. Radiasi ................................................................................. 16 E. Perpindahan Kalor Sensibel dan Kalor laten ............................ 17 1. Pemanasan Sensibel ............................................................ 17 2. Beban kalor Laten ............................................................... 17 3. Kalor Total .......................................................................... 17 4. Campuran Udara dan Uap Air............................................. 18 F. Istilah-Istilah Suhu .................................................................... 18 1. Suhu Bola kering ................................................................. 18 2. Suhu Bola Biasa .................................................................. 18 3. Proses Kelembaban Udara .................................................. 19 G. Parameter Pengeringan.............................................................. 20 1. Suhu Udara Pengering......................................................... 20 2. Kelembaban Relatif (RH) Udara Pengering ....................... 20 3. Kecepatan Aliran Udara Pengering..................................... 20 4. Kadar Air Bahan ................................................................. 21 5. Aliran Udara Pengering....................................................... 22 6. Karakteristik Pengeringan Jagung....................................... 23 7. Sorpsi Isotermi .................................................................... 24 8. Aktivasi Air ......................................................................... 24 H. Perhitungan Teknis Kinerja pengeringan .................................. 25 1. Analisa Kadar Air ............................................................... 25 2. Analisa Kebutuhan Energi Selama Proses Pengeringan ......................................................................... 26 a. Kebutuhan Energi Untuk Pengeringan Jagung (Qd), Kkal ............................................................................... 26 b. Energi Yang Hilang Dari Dinding Penutup (Qlt), kkal ................................................................................ 26

c. Total Energi yang Dibutuhkan Untuk Mengeringkan Jagung Per Siklus (Qt), kkal.................. 27 3. Laju Pengeringan ................................................................ 27 a. Periode Laju Konstan .................................................... 28 b. Periode Laju Jatuh ......................................................... 28 c. Persamaan Laju Pengeringan ........................................ 29 I. Perhitungan Teknis Komponen-Komponen Mesin ................... 30 1. Perhitungan Tebal Pengeringan .......................................... 30 2. Perhitungan Kecepatan Conveyor ....................................... 30 3. Mencari Putaran Poros ........................................................ 31 4. Mencari Putaran Motor ....................................................... 31 5. Perhitungan Kapasitas Pengangkutan Belt Conveyor ......... 31 6. Menghitung Tegangan Pada Belt ........................................ 32 a. Perhitungan Teganan Tegang dan Tegangan Kendur ........................................................................... 32 b. Perhitungan Untuk Tegangan Maksimum Pada Belt Conveyor ....................................................................... 33 c. Perhitungan Diameter Poros Conveyor/ Pully Idler ...................................................................... 33 7. Bantalan............................................................................... 33 a. Perhitungan Beban dan Umur bantalan......................... 33 1) Perhitungan Beban Ekuivalen ................................. 33 2) Perhitungan Umur Nominal .................................... 34 8. Sabuk dan Puli .................................................................... 35 a. Perbandingan Putaran dan Diameter Puli ..................... 36 b. Panjang Sabuk ............................................................... 36 c. Kecepatan Linier Sabuk ................................................ 36 d. Jarak Antara Sumbu Poros Puli (C) .............................. 36 e. Tegangan Sabuk ............................................................ 37 f. Sudut Kontak Antara Sabuk Dengan Puli Penggerak ...................................................................... 37

g. Daya Yang Dapat Ditransmisikan Oleh Sabuk ............. 37 h. Besar Sudut ................................................................... 37

BAB III

PEMBAHASAN ............................................................................ 38 A. Komponen-komponen Utama Mesin ........................................ 38 1. Rangka Mesin ..................................................................... 38 2. Belt Conveyor ..................................................................... 38 3. Roller (Pully Idler) .............................................................. 39 4. Poros Pully Idler .................................................................. 39 5. Bantalan............................................................................... 40 6. Frame Penutup .................................................................... 40 7. Baut Setelan ........................................................................ 40 8. Kopling................................................................................ 41 9. Gear Box ............................................................................. 41 10. Motor Listrik ....................................................................... 42 11. Sensor Suhu......................................................................... 42 12. Hot Gun ............................................................................... 43 B. Prinsip Kerja Mesin .................................................................. 43 C. Perhitungan Teknis Proses Pengeringan ................................... 44 1. Perhitungan kadar Air ......................................................... 44 2. Berat Jagung Awal (Wi), kg ................................................ 44 3. Total Energi yang Dibutuhkan ............................................ 45 4. Kebutuhan Energi Untuk Pengeringan Jagung (Qd) ........... 46 5. Energi yang Hilang Dari Pelat Dinding Pengering ............. 47 6. Total Energi yang Dibutuhkan Untuk Mengeringkan Jagung Per Siklus (Qt) ......................................................... 49 7. Laju Pengeringan ................................................................ 49 D. Perhitungan Teknis Komponen Mesin ...................................... 49 1. Mencari Tebal Pengeringan ............................................... 49 2. Mencari Kecepatan Belt Conveyor ..................................... 51 3. Mencari Putaran Poros ........................................................ 51

4. Mencari Putaran Motor ....................................................... 51 5. Mencari Daya Rencana Motor ............................................ 52 a. Daya Untuk Menggerakkan Sabuk ............................... 52 b. Daya Rencana Untuk Motor.......................................... 52 c. Daya Untuk Menggerakkan Poros ................................ 53 1) Cari Berat Poros Pully Idler .................................... 53 2) Cari Berat Puli ......................................................... 53 3) Cari Berat Penutup Lubang Puli ............................. 54 4) Cari Berat Total Roller Conveyor ........................... 54 5) Tegangan-Tegangan Pada Belt ............................... 55 a) Tegangan Tegang dan Tegangan Kendur ......... 55 b) Tegangan Maksimum Pada belt ........................ 56 d. Mencari Diameter Poros Roller Conveyor/ Pully Idler ...................................................................... 56 1) Beban Poros Dari Belt Conveyor ............................ 56 2) Beban Dari Puli ....................................................... 56 3) Beban Poros dari Penutup Pully.............................. 56 4) Diagram Gaya ......................................................... 57 5) Tegangan Normal Maksimum pada Poros .............. 57 e. Umur Bantalan .............................................................. 58 E. Perhitungan Data Percobaan (Sampel)...................................... 59 F. Penggunaan Mesin .................................................................... 60

BAB IV

PROSES PEMBUATAN DAN ANALISA BIAYA .................... 61 A. Pemilihan Bahan Untuk Komponen Mesin............................... 61 1. Rangka Mesin ..................................................................... 61 2. Roller ................................................................................... 61 3. Frame Penutup, Hopper, dan Outlet .................................... 61 4. Belt Konveyor ..................................................................... 62 5. Kopling Flens ...................................................................... 62 B. Proses Pembuatan Mesin .......................................................... 62

1. Rangka Mesin ..................................................................... 62 2. Roller ................................................................................... 63 a. Pully Idler ...................................................................... 63 b. Poros Idler ..................................................................... 63 c. Penutup Lubang Pully Idler .......................................... 63 3. Frame Penutup .................................................................... 64 4. Belt Conveyor ..................................................................... 64 5. Kopling Flens ...................................................................... 65 C. Perhitungan Waktu Pengerjaan ................................................. 65 1. Perhitungan Waktu Kerja Mesin Bubut Untuk Pembubutan Idler Roller .......................................................................... 65 a. Teori Perhitungan Waktu Pembubutan ......................... 65 b. Analisa Perhitungan Waktu Pengerjaan Poros Idler ..... 66 2. Perhitungan Total Waktu yang Dibutuhkan Untuk Pembuatan Mesin ................................................................ 67 D. Analisa Biaya ............................................................................ 68 1. Biaya Bahan ........................................................................ 68 2. Biaya Alat............................................................................ 69 3. Biaya Jasa ............................................................................ 69 4. Biaya Listrik ........................................................................ 69 5. Biaya Pembuatan ................................................................. 70 a. Biaya Pembuatan Rangka Mesin .................................. 70 b. Biaya Pembuatan dan Perakitan Mikrokontroller ......... 71 6. Total Biaya Pembuatan Mesin ............................................ 71 7. Harga Jual Model Pengering Jagung................................... 72 8. Analisis Titik Impas ............................................................ 72 a. Biaya Tetap (B.T).......................................................... 72 b. Harga Jual (H.J) ............................................................ 72 c. Biaya Variabel (B.V) .................................................... 73

BAB V

PERAWATAN DAN PERBAIKAN ............................................ 75 A. Perawatan dan Perbaikan .......................................................... 75 1. Pengertian Perawatan dan Perbaikan .................................. 75 2. Tujuan Perawatan dan Perbaikan ........................................ 75 B. Perawatan dan Perbaikan Pada Prototype Mesin Pengering Jagung Sistem Konveyor .......................................................... 75 1. Perawatan Prediktif ............................................................. 76 2. Perawatan Preventif ............................................................ 76 C. Perawatan dan Perbaikan Komponen-Komponen Utama Mesin ............................................................................. 76 1. Perawatan Pada Bantalan .................................................... 76 2. Perawatan Pada Puli ............................................................ 77 3. Perawatan Pada Sabuk ........................................................ 77 4. Perawatan Pada Belt Conveyor ........................................... 77 5. Perawatan Pada Kopling Tetap ........................................... 78 6. Perawatan Pada Gear Box ................................................... 78 7. Perawatan Pada Motor ........................................................ 78 8. Perawatan Pada Rangkaian Mikrokontroller ...................... 78 9. Perawatan Pada Hot Gun .................................................... 78

BAB VI

KESIMPULAN DAN SARAN ..................................................... 79 A. Kesimpulan ............................................................................... 79 B. Saran .......................................................................................... 79

DAFTAR PUSTAKA

LAMPIRAN

DAFTAR GAMBAR Gambar 1. Jagung.................................................................................................. 5 Gambar 2. Pemanenan Pengeringan Jadi Biji Jagung......................................... 11 Gambar 3. Proses Pengeringan Pada Kurva Psicometric .................................... 12 Gambar 4. Konstruksi Sabuk V .......................................................................... 35 Gambar 5. Ukuran Penampang Sabuk V ............................................................ 35 Gambar 6. Mesin Pengering Biji Jagung ............................................................ 38 Gambar 7. Belt Conveyor ............................................................................. .... 39 Gambar 8. Pully Idler dan Penutup Pully Idler Untuk Tumpuan Poros.............. 39 Gambar 9. Poros Pully Idler ................................................................................ 39 Gambar 10. Bantalan Gelinding G206 ................................................................ 40 Gambar 11. Frame Penutup................................................................................. 40 Gambar 12. Baut Setelan..................................................................................... 41 Gambar 13. Kopling Flens .................................................................................. 41 Gambar 14. Gear Box Dengan Ratio 1 : 30 ........................................................ 42 Gambar 15. Motor AC 0,5 Hp ........................................................................... 42 Gambar 16. Hot Gun Sebagai Sumber Panas...................................................... 43

DAFTAR TABEL Tabel 1. Komposisi kimia dan Zat Gizi Jagung Kuning Pipilan............... 8 Tabel 2. Standar Mutu Jagung .................................................................. 9 Tabel 3. Tebal Pengeringan Untuk Kapasitas Berbeda ...................... ...... 50 Tabel 4. Data Laboratorium Hasil Percobaan ........................................... 60 Tabel 5. Lama Pengerjaan Untuk Pembuatan Mesin ................................ 67 Tabel 6. Nama Bahan dan Biaya Bahan.................................................... 68 Tabel 7. Nama Alat dan Harga Alat .......................................................... 69 Tabel 8. Biaya Jasa .................................................................................... 69 Tabel 9. Biaya Penggunaan Listrik ........................................................... 70

DAFTAR LAMPIRAN

Lampiran 1. Diagram Pemilihan Sabuk-V Lampiran 2. Sabuk-V Standar Lampiran 3. Faktor- Faktor Koreksi Daya Yang Akan Ditranmisikan , fc Lampiran 4. Ukuran Puli-V Lampiran 5. Koefisien Gesek Lampiran 6. Panjang Sabuk-V Standar Lampiran 7. Bantalan Lampiran 8. Konduktivitas Termal Berbagai Bahan Lampiran 9. Panas Jenis Bahan Atau Material Lampiran 10. Berat Belt Standart ,W1 Lampiran 11. Diagram Psikometrik Lampiran 12. Emisivitas Total Normal Berbagai Permukaan Lampiran 13. Emisivitas Total Normal Berbagai Permukaan (Lanjutan) Lampiran 14. Faktor Konversi Lampiran 15. Konversi Satuan Lampiran 16. Hasil Analisa Kadar Air Jagung