How to Prepare a Process Design Basis Take care not to overlook anything when preparing this document, which is vital for spelling out a well-planned chemical-process project. The checklists and tables in this article can serve as remind Anthony Pavone SRI Consulting
Intelligent — and thorough — preparation of a process-design-basis document can make the difference between a high-quality design for a chemical-process project and a poor one. The processdesign-basis document represents the owner’s instructions to the design engineering organization about what the owner wants designed and how the owner wants the process design to be done. !ote that these instructions to the process design engineering effort are different from what the owner would pro"ide to the basic design#mechanical engineering organization or the design-construct organization. !ote also the distinction between a process-design-basis document and a scope-of-work document. The scope of work is an integral part of the design basis but the design basis also contains much more. The scope of work defines what is to be done and what are the limits of that acti"ity. The design basis also pro"ides the who the how the why and the when. $urthermore the scope of work rarely addresses the design philosophy the design standards the e%ecution plan the format of deli"erables or the commercial terms.
Don’ t leave anything out & fundamenta fundamentall attribute of a good process-desig process-design-basis n-basis document document is that nothing nothing important important be omitted. The owner’s engineer who is charged with producing such a document accordingly must gi"e at least initial if not detailed attention to all of an e%tensi"e list of project aspects'
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The o"erall plant objecti"e
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The products that the plant will produce
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The process technology to be used
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(rocess control philosophy
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The management of the project
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The project contract
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The process design deli"erables and their format
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)ow information will flow between the parties during the project
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(referred "endors if any
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*onduct of the process design engineers
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The nature of the plantsit &ny unusual economic criteria
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The offsite facilities and the infrastructure requirements
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+rownfield-site compatibility
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,n"ironmental safety and "essel- and structural-design standards permits and requirements
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(lant operation and maintenance philosophy
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wner’s wishes regarding working capital
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The communication system for the completed plant
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The security of the project and of the completed plant
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(roject e%ecution e%pectations
Objectives, products, control, management ome projects are financed with in"estment adequate to encourage a long plant operating-life ma%imum run-time between turnarounds minimal labor intensity easy switches between product grades and minimal bottlenecks during operation. &t the other e%treme the owner’s objecti"e is instead to build the lowest-capital-cost plant that can meet capacity and product specifications. It is important for the process design organization to know the owner’s intentions o"er this capital-outlay spectrum. &lso of primary importance is the product slate that the finished plant is to produce. )ow much of each product is to be made /in tons#year bottles#day or other units01 2hat specifications must the product satisfy1 &re there different product grades to be made3 if so what are the specifications and how much of each grade is to be made1 )ow are the final products to be stored packaged and then transported to customers1 If a particular process technology is to be used say so in the document. n the one hand this might be a particular licensed commercial technology3 on the other hand the specifics of the process might not be known at this early stage. The standards to be used for the process design are set by the owner not the design organization. These standards include the following'
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4oad bearing standards /piling spread footings0
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tructural support standards
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tructural integrity standards
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(ressure-"essel design standards /&5,0
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$ire protection standards /!$( 640
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,quipment standards /&(I 7I! &!I other0
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Testing standards /e.g. &T50
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,lectrical standards /I,,, !,* 640
The process control philosophy to be used in the finished plant as well as the type of system to be considered for super"isory control and data acquisition /*&7&0 system should be specified in terms of either performance or specific selection by the owner. The le"el of data communication between the process control function the onsite engineering and the maintenance facilities is also to be defined. In many cases an operating company will standardize on one particular process-control "endor in order to a"oid the need for staff cross-training. If a "endor has been designated by the owner this should of course be specified in the design basis document. 2ith respect to the management of the project the process-design-basis document should identify the owner’s authorized person for appro"ing all design acti"ities. The management chains of command on both the owner’s side and the engineering organization’s side should likewise be spelled out. &ppro"al mechanisms /embodied in for instance change orders0 for all acti"ities /changes inside scope and changes outside scope0 that would incur additional cost for the project are defined. The nature and format of the design deli"erables are to be defined /these two topic are each discussed in more detail below0. The frequency of progress reports and how they are to be presented must be spelled out. The project schedule must be defined. &nd for most projects the document should insist on prior appro"al in writing before any commitments are made to outside "endors that could incur future costs or liabilities to the project. The legal contract between the owner and the process design engineer must incorporate all the relationship requirements for a successful outcome. In addition to ones specified in the preceding paragraph these in"ol"e details concerning the periodic and end-of-job payments as well as con"ersely the interim and final process engineering deli"erables to justify those payments. e"eral elements that should be addressed in a good contract include those listed in Table 8.
Deliverables: content, format The specifics and the format of the process design deli"erables need to be e%plicitly stated in the design basis document. 9ey elements include those shown in Table :. &s noted in Table : one of the items among the deli"erables should be an input#output diagram that defines the major inputs to this plant /what feedstocks and their specifications what utilities and other production inputs such as additi"es and catalysts0 as well as the major outputs. In most cases the quantification of all of these materials is not yet known at this stage but the nature of the inputs and outputs should be defined to the process design organization. ormat: wners are entitled to conformance with specific formats for engineering deli"erables in order to satisfy companywide and industrially recognized standards. The format generally addresses such aspects as the following criteria and guidelines'
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6nits of measure to be used /metric ,nglish0
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tandardized engineering-drawing symbols
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,quipment numbering and tagging nomenclature
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Instrumentation and control symbols
6nits of identification for bulks and non-,’s /bulk equipment represents simple hardware bought in large amounts without specific equipment numbers. These items often include block "al"es sample and drain "al"es piping switches illumination walkways and railings cable and its housing. !on-,’s or non-equipment represent other materials required to be purchased and consumed on a job such as concrete asphalt structural and reinforcing steel insulation coatings and welding rod0 •
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tandardized piping line lists and tie-in lists
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5aterial balance formats
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,quipment and piping one-page process spec sheets
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(ressure "essel and tank drawings
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,lectrical one-line drawings
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*ontrol loop drawings
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The size paper to be used for reports
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The size paper to be used for drawings
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Type-font and letter size
;equirement and format for "endor cuts /paper drawings pictures descripti"e material dimensions and specifications of specific equipment pro"ided by a specific "endor0 •
wners are also entitled to demand the use of industry-wide non-proprietary computer software for generating engineering deli"erables. ne reason for this standardization is to allow computerized translation from one software package to another. This entitlement pertains to the software used for planning and scheduling cost estimating process design piping network analysis process simulation computer-aided :7 and <7 design and the preparation of written reports.
Project communication The process design basis document should include a contract communication specification /**0. It defines how information will flow and be shared during project e%ecution.
The ** is designed to minimize communication misunderstandings and misinterpretations and to assure that all members of the project organization are continuously working off the most current set of design documents. The ** is also intended to optimize the amount of time and effort e%pended for communication between client and engineer between members of the design engineering organization and with third parties that are in"ol"ed in the process design. These third parties typically include go"ernmental regulators subcontractors client employees not directly in"ol"ed in the project financial institutions "endors and suppliers. 9ey elements of the ** include those shown in Table <. /*ommunication in"ol"ing the plant operating personnel after the plant is up and running is a separate issue also to be addressed in the process design basis document as discussed below.0 !endors and engineers wners are entitled to pro"ide to the design engineering organization a list of preferred or appro"ed "endors pro"ided that these "endors operate where the plant is to be built and that their products conform to internationally recognized engineering standards /&(I 7I! ,6 for instance0. The engineering organization is required to de"elop its design in a manner consistent with the use of such preferred "endors3 con"ersely the owner is required to pro"ide at least three preferred "endors for each major kind of equipment to a"oid issues in"ol"ing monopoly pricing or proprietary equipment designs. 5eanwhile the design basis document should also address any issues regarding the conduct that is e%pected of the design organization’s personnel. 9ey elements to be addressed include the following'
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&uthorizations to "isit plantsite
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&uthorizations to "isit owner’s headquarters site
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uitable attire for "isits to plant and owner’s site
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(ersonnel protecti"e equipment for plantsite "isits
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Issues in"ol"ing any cultural sensiti"ities3 non-discrimination standards
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wner’s policy on ethics
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7esign-team company’s policy on ethics
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7rugs and alcohol policy and standards
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*ontrolled-substance policy and standards
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(olicy and reporting requirements for bribery /+usiness ;oundtable standards0
Plantsite, offsites, infrastructure The site chosen for the production facility is to be defined e%actly. 2here is it1 2hy was it chosen1 2hat are the particular characteristics of this site that ha"e led the owner’s management team to select it1 Is the site a greenfield one or a brownfield one1 Issues related to brownfield sites are discussed separately in detail below.
ite-specific and unusual characteristics of the plantsite need to be communicated to the project organization. 9ey characteristics of the site that need to be spelled out include those in Table =. "nusual economic criteria: 5ost engineering-design criteria implicitly contain assumptions dealing with pre"ailing economic conditions. These assumptions are rarely documented. If a particular plantsite in"ol"es unusually high cost elements these should be identified such that the design organization can modify its design criteria accordingly. ome common economic factors and the design criteria they affect are listed in Table >. Offsites: ffsites for utilities and accessory facilities are to be defined by the owner in terms of performance. The design engineering organization will con"ert this input into engineering design specifications. Typical offsite facilities include those in Table ?. #nfrastructure re$uirements% If facilities outside of the main process plant plus its offsite utility facilities are required these need to be specified to the design organization. These infrastructure requirements may well include outside docks#piers#siding facilities transshipment and other recei"ing facilities for feedstock and chemicals and facilities to ship product to the customer. If intermediate warehousing facilities are required away from the plant site this requirement needs to be defined. *ogeneration seawater-desalting or other facilities pro"iding utilities to the site are likewise to be spelled out. &ny sharing of facilities between industrial plants in a community /fire protection security utilities0 should also be defined and specified by the owner. Brownfield site compatibility: If the project is to be built at a site with e%isting facilities such that these e%isting facilities are e%pected to be used or a"ailable to the project the demonstrated — not design — capabilities of the e%isting facilities are to be documented so that the engineering organization can design the new plant to be consistent with e%isting facilities. & key component of the design basis document is a tie-in list that shows what facilities are a"ailable e%actly where they are a"ailable /location specific battery limits0 and their capabilities. ,%isting-facility a"ailability should include these items'
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pare infrastructure capacity
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pare utility capacity
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pare tankage capacity
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$irewater a"ailability and pressure
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(otable-water a"ailability pressure
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(rocess-water a"ailability pressure
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;aw-water and#or seawater a"ailability and pressure
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+oiler-feedwater a"ailability pressure composition /T7 conducti"ity0
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$lare and flare-header a"ailability and spare capacity
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&"ailable steam flowrates pressures and degrees of superheat
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&"ailable capacity and pressure of inert gas and instrument air
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$uel-gas and fuel-oil a"ailability and pressure
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,lectric system a"ailability /sub-station location capacity "oltage phase frequency0
&nvironment, safety The pre"ailing legal standards co"ering en"ironmental protection need to be indicated. These are likely to include some or all of the issues in Table @. The consequent plant-performance requirements and en"ironmental-permit requirements must also be spelled out by the owner . 4ikely major requirements to be addressed include some or all of those related to the list in Table A. 2ith respect to safety the design standards and the procedures to be utilized to assure inherently safe design construction and operation are to be specified by the owner. ,lements incorporated in many design basis documents include those in Table B. Operation, maintenance The owner is required to inform the engineering organization of the operation-and-maintenance /C50 philosophy to be reflected by the process design. *omponents of this philosophy include the following'
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,%pected run length between scheduled turnarounds
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,%pected equipment runtime between mean failure
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4e"el of automatic instrumentation to be pro"ided that is not needed for control
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;edundant online equipment
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;edundant offline equipment
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4e"el of equipment sparing that is inline
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4e"el of equipment sparing that is warehoused
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,quipment-dri"er selection and philosophy
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7ual dri"ers for critical process equipment
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$acilities to be pro"ided with un-interruptible power supplies /6(0
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,quipment-rebuild capabilities onsite
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,quipment rebuild capabilities to be shopped out
'urndown capability: The plant is designed for a nameplate capacity /in for instance metric tons per year0 at a particular ser"ice factor /operating hours per year di"ided by A@?D hours per year0. <hough the plant is designed for optimal operation at a particular throughput rate /stream-day flowrate0 business conditions may dictate that the plant run at substantially lower-than-design rate for an indefinite period of time. This turndown ratio should be specified by the owner. There may also be short-term periods /days not weeks0 in which the plant should be capable of running abo"e nameplate capacity in order to reco"er from outages or build in"entory in preparation for turnaround. This turnup ratio should also be specified.
(or)ing capital: The owner must pro"ide instructions to the engineering organization as to the design basis philosophy for the working capital to be maintained in the plant. uch working capital includes' the number of days storage for feedstock intermediate and final products3 the additi"es in"entory in-process and in-storage catalyst quantities and spare-catalyst charge requirements3 and the inline equipment spares warehoused equipment spares parts spares and construction#maintenance equipment. The owner should pro"ide instructions on the choice of purchased equipment "ersus leased equipment especially for fleet and construction "ehicles distributor held spares and ,5 held spares. *ommunication system: The owner should pro"ide guidance as to the preferred system for in-plant and e%-plant communication for the completed and operating facility including both fi%ed-line and mobile-line capability and capacity. If a system operator is required the owner should specify the reporting requirements for that operator /usually part of plant security0. ,%ternal communications capabilities with the owner’s headquarters and with local law enforcement en"ironmental regulators coast-guard and marine officials and go"ernmental officials should be specified in terms of who is to be contacted how by whom and under what circumstances. 7ocumentation needs for e%-plant communications are also to be specified. +ecurity% tandards to protect the plant from unauthorized destructi"e actions by either local malcontents or national or international terrorists need to be addressed. The primary issues affect the following'
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,quipment layout
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(lant access
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,mergency and countermeasure plans
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ecurity fencing
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ecurity people
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(ersonnel hiring#screening procedures
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ecurity communications network /e%-plant0
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*oordination with local law enforcement
Project eecution The focus of this article has been upon process design. +ut the process design organization is in many instances contracted to pro"ide to the owner a plan for e%ecuting the balance of the project including mechanical and structural design construction startup and commissioning. The owner’s e%pectations as to the le"el of detail required is to be specified to the engineer and guidance should be pro"ided for the planning components in Table 8D. ,dited by !icholas (. *hopey
