01 Pengantar Disain

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Pengantar Disain

Abdul Wahid Surhim 2012Pengantar Disain

Rujukan Towler, G. and Sinnott, R. 2008. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. Elsevier Chapter 1 INTRODUCTION TO DESIGN

Kerangka PembelajaranBatasan DisainProses DisainAnatomi Proses KimiaStruktur Proyek Rekayasa KimiaDokumentasi ProyekKode dan StandarFaktor DisainSistem SatuanOptimisasi

Batasan Disain

Design is an inexact artDesign is a creative activity

External ConstraintsThe constraints that are outside the designers influence can be termed the external constraintsSome constraints will be fixed and invariable, such as those that arise from physical laws, government regulations, and standards. Others will be less rigid and can be relaxed by the designer as part of the general strategy for seeking the best design.Economic considerations are obviously a major constraint on any engineering design: plants must make a profit

Internal Constraints Within this boundary there will be a number of plausible designs bounded by the other constraints, the internal constraints, over which the designer has some control, such as choice of processchoice of process conditions, materials, and equipmentTime will also be a constraint. The time available for completion of a design will usually limit the number of alternative designs that can be considered

Disain Proses

The Design Objective (The Need)All design starts with a perceived need. In the design of a chemical process, THE NEED is the public need for the product, creating a commercial opportunity, as foreseen by the sales and marketing organization. Within this overall objective, the designer will recognize sub objectives, the requirements of the various units that make up the overall processIt is important to distinguish between the needs that are must haves and those that are should haves. The should haves are those parts of the initial specification that may be thought desirable, but that can be relaxed if required as the design developsIt is important to make sure that all of the designs that are considered are fit for the service, i.e., meet the customers must have requirements

The Need: Supply-Demand AnalysisUntuk melihat KEBUTUHAN dapat dilakukan dengan SUPPLY-DEMAND ANALYSISDemand >> Supply Perlu PRODUKSI yang lebih besar lagiCara menentukan permintaan:Time-series AnalysisRegressionEconometrics

Setting the Design BasisThe design basis is a more precise statement of the problem that is to be solved. It will normally include the production rate and purity specifications of the main product, together with information on constraints that will influence the design, such asThe system of units to be used.The national, local or company design codes that must be followed.Details of raw materials that are available.Information on potential sites where the plant might be located, including climate data, seismic conditions, and infrastructure availability. Information on the conditions, availability, and price of utility services such as fuel (gas), steam, cooling water, process air, process water, and electricity, that will be needed to run the process

Generation of Possible Design ConceptsThe creative part of the design process is the generation of possible solutions to the problem for analysis, evaluation, and selection. In this activity, most designers largely rely on previous experiencetheir own and that of others. It is doubtful if any design is entirely novel. The antecedents of most designs can usually be easily traced

Generation of Possible Design ConceptsChemical engineering projects can be divided into three types, depending on the novelty involved:Modifications, and additions, to existing plant; usually carried out by the plant design group.New production capacity to meet growing sales demand and the sale of established processes by contractorsNew processes, developed from laboratory research, through pilot plant, to a commercial process

Fitness TestingWhen design alternatives are suggested, they must be tested for fitness of purpose. In other words, the design engineer must determine how well each design concept meets the identified need. In the field of chemical engineering, it is usually prohibitively expensive to build several designs to find out which one works best (a practice known as proto-typing, which is common in other engineering disciplines). Instead, the design engineer builds a mathematical model of the process, usually in the form of computer simulations of the process, reactors, and other key equipment

Economic Evaluation, Optimization, and SelectionOnce the designer has identified a few candidate designs that meet the customer objective, then the process of design selection can begin. The primary criterion for design selection is usually economic performance, although factors such as safety and environmental impact may also play a strong roleThe economic analysis of the product or process can also be used to optimize the design

Detailed Design and Equipment SelectionAfter the process or product concept has been selected, the project moves on to detailed design.Here the detailed specifications of equipment such as vessels, exchangers, pumps, and instruments are determined. The design engineer may work with other engineering disciplines, such as civil engineers for site preparation, mechanical engineers for design of vessels and structures, and electrical engineers for instrumentation and controlMany companies engage specialist Engineering, Procurement, and Construction (EPC) companies, commonly known as contractors, at the detailed design stage

Procurement, Construction, and OperationWhen the details of the design have been finalized, the equipment can be purchased and the plant can be built. Procurement and construction are usually carried out by an EPC firm unless the project is very smallFinally, once the plant is built and readied for startup, it can begin operation. The design engineer will often then be called upon to help resolve any startup issues and teething problems with the new plant.

Anatomi Proses Kimia

Struktur Proyek Rekayasa Kimia

Struktur Proyek Rekayasa Kimia

Dokumentasi ProyekGeneral correspondence within the design group and withGovernment departmentsEquipment vendorsSite personnelThe clientCalculation sheetsDesign calculationsCost estimatesMaterial and energy balancesDrawingsFlowsheetsPiping and instrumentation diagramsLayout diagramsPlot/site plansEquipment detailsPiping diagrams (isometrics)Architectural drawingsDesign sketchesSpecication sheetsThe design basisFeed and product specicationsAn equipment listSheets for equipment, such as heat exchangers, pumps, heaters, etc.Health, Safety and Environmental information:Materials safety data sheets (MSDS forms)HAZOP or HAZAN documentation (see Chapter 9)Emissions assessments and permitsPurchase ordersQuotationsInvoices

Kode dan StandarStandar pertama diperkenalkan oleh Whitworth pada tahun 1841Tujuannya adalah untuk memberikan ukuran interchangeability antar manufaktur yang berbedaStandar modern mencakupMaterials, properties, and compositions.Testing procedures for performance, compositions, and quality.Preferred sizes; for example, tubes, plates, sections, etc.Methods for design, inspection, and fabrication.Codes of practice for plant operation and safety

Kode dan StandarIstilah Standar dan Kode digunakan secara bertukaran, meskiKODE seharusnya digunakan untuk kode praktis yang mencakup, katakanlah, disain yang direkomendasikan atau prosedur operasiSTANDAR untuk ukuran (sizes), komposisi, dll yang disukaiSNI (Standar Nasional Indonesia)American National Standards Institute (ANSI)American Petroleum Institute (API)American Society for Testing Materials (ASTM)American Society of Mechanical Engineers (ASME) (pressure vessels and pipes)National Fire Protection Association (NFPA; safety)Instrumentation, Systems and Automation Society (ISA; process control)International Organization for Standardization (ISO)

Kode dan StandarTUGASCari contoh kode atau standar untuk peralatanKirimkan filenya ke: ahad767@gmail.com Tugas kelompok (maks 3 orang)Diserahkan PEKAN DEPAN

Faktor Disain (Marjin Disain)Kesalahan dan ketidakpastian muncul dari ketidakpastian ketersediaan data disain, dankeperluan pendekatan dalam perhitungan disainPerancang yang berpengalaman memasukkan tingkat kelebihan disain yang disebut design factor, design margin, atau safety factor, untuk memastikan bahwa disain yang dibangun sesuai dengan spesifikasi produk dan beroperasi secara aman

Sistem Satuan

Optimisasi Obyektif disainBatasan dan derajat kebebasanTitik temu (trade-offs)Dekomposisi masalahOptimisasi variabel disain tunggalMetode pencarianOptimisasi dua variabel disain atau lebihLinear programmingNonlinear programmingMixed Integer ProgrammingOptimisasi dalam praktek industri