- By Vilas Desai, Steve Mustard
An automated, standards-based documentation process saves time and cost while increasing quality.
The production of design and engineering documents for automation projects is expensive and time consuming, and the output quality can vary considerably, because often the processes are mostly manual. However, many tools are available that can reduce time and cost, while increasing documentation quality. Engineering, procurement, and construction (EPC) contractors, instrumentation engineers, consultants, and others use these tools in projects, and educational institutions use them to train the next generation of users.
The centralization and automation of document production saves time and money and removes many manual, error-prone steps. Combining these tools with international standards makes the output more consistent across end user, EPC, sector, and country. Many instrumentation engineers are accustomed to manual methods for creating the complex engineering and design documents and drawings required for typical process industry projects. These manual methods are inefficient, expensive, and subject to human error.
A typical small process industry project with 1,000 input/output (I/O) tags may spend more than six months producing required documentation, incurring costs of around $150,000, assuming no errors. Medium and large projects will see proportional increases in these costs and timescales. Problems identified and corrected later in the project may significantly contribute to project cost overruns.
Changes are common to any automation project, whether to correct errors or to address new functional requirements. Change management is a major challenge to project cost and timescale. Managing changes through manual processes is prone to error and consumes a major portion of project implementation time.
Project documentation requirements
At a minimum, a typical process industry instrumentation project needs the following engineering and design documents:
- Instrument index: A database for all devices documented in process flow diagrams (PFDs) and piping and instrumentation diagrams (P&IDs) (figure 1).
- Junction box schedules: Information about specifications and quantity of junction boxes, the number of terminals of different sizes, the dimension of the junction box, along with construction, glands, and ingress protection of cables used in the project.
- Cable schedule: Details regarding types of cables used, number of cores, size, and length of various cable types.
- Wiring diagrams: Indication of how to wire instruments into junction boxes, marshalling racks, control panels, and I/O channels of the programmable logic controllers (PLCs) or distributed control systems (DCSs).
- Terminal diagrams: Details of the connection of wires to terminal numbers inside the junction box, marshalling rack, and control panel.
- Device specification forms: Specification of details of all devices used in the project, such as project, client information, general parameters, process conditions and parameters, construction, standards, process connections, communications, and purchase details.
- PLC/DCS I/O listing: A list in tabular form of inputs and outputs required for the PLC and DCS.
- Loop diagrams: Engineers and technicians use these diagrams to ensure all the equipment wiring is in accordance with the design documents (cable schedule, wiring diagrams, and terminal diagrams).
- Hookup drawings: Details of the mounting and connection of field devices to the process.
Currently, instrument engineers use several tools to produce project documentation, with Microsoft Excel and AutoCAD being the most widely used. Excel is well-suited to produce information lists, and there are many functions, such as filtering and searching, that can aid users when accessing the information. Excel works well for projects with small I/O counts and can potentially produce many of the list documents described above, such as instrument index, schedules, and I/O listings.
Excel has limited drawing capabilities. Tools such as AutoCAD are more suitable for producing loop diagrams, hookup drawings, PFDs, and P&IDs. AutoCAD is a computer-aided design (CAD) tool used across multiple sectors to produce engineering drawings. Table 1 lists the limitations of current tools related to scalability, lack of centralization, and required skills.
|Scalability||Lack of centralization||Skill requirements|
|There are limits in many commercial tools. There is a limit of 65,536 rows in older versions of Excel. Newer versions support 220 rows, but at this size, the performance of the application is unacceptable on most desktop computers.||It is often necessary to use multiple tools because one alone cannot produce all the documents required. Using multiple tools can create discrepancies in output from the different tools.||AutoCAD requires substantial user experience to produce the typical project drawings described. Creating the project documents needed in Excel requires user knowledge of macros, Visual Basic, and other Microsoft automation tools.|
Standards are fundamental
ISA is a standards development organization (SDO) accredited by the American National Standards Institute (ANSI). ISA produces standards for the automation profession, including standards governing symbols and nomenclature, safety, and communications. ISA has been creating standards for more than 75 years and has produced several publications to ensure automation professionals have the technical resources they need to be successful. Engineering and automation professionals use ISA standards in their day-to-day work designing PFDs, P&IDs (figure 2), instrument indexes, specification forms/data sheets, logic diagrams, and loop diagrams.
Instrumentation documentation must follow all applicable company, sector, and country standards. The use of ISA standards ensures a consistent approach across company, sector, and country. The ISA website has a complete list of all ISA standards, and ISA members have read-only access to all ISA standards. Some standards that ISA produces relating to instrumentation documentation include:
- ISA-5.1-2009, Instrumentation Symbols and Identification: Establishes a uniform means of depicting and identifying instruments or devices and their inherent functions, instrumentation systems and functions, and application software functions used for measurement, monitoring, and control, by presenting a designation system that includes identification schemes and graphic symbols.
- ISA-5.4-1991, Instrument Loop Diagrams: Establishes minimum required information and identifies additional optional information for a loop diagram for an individual instrumentation loop. This loop is typically part of a process depicted on the class of engineering drawings referred to as piping and instrument drawings. This standard gives guidelines for the preparation and use of instrument loop diagrams in the design, construction, startup, operation, maintenance, and modification of instrumentation systems.
- ISA-20-1981, Specification Forms for Process Measurement and Control Instruments, Primary Elements, and Control Valves: Provides forms (checklist) to promote uniformity in instrument specification—both in content and form—by listing and providing space for principal descriptive options. These forms facilitate quoting, purchasing, receiving, accounting, and ordering procedures.
With standards-driven processes and workflows comes the assurance of following the best industry practices during the definition, design, development, integration, documentation, and support of automation projects. This ensures the execution of projects with precision and standardization. Benefits to a project include:
- assisting in preparation of a complete specification by listing all principal descriptive options
- promoting uniform terminology
- facilitating procedures for quoting, purchasing, receiving, accounting, and ordering by uniform display of information
- improving efficiency from the initial concept to the final installation.
Automating the documentation process
Considering the limitations of existing methods, an automated solution should:
- be scalable to allow the documentation of the largest process industry projects
- centralize all data, so there is less scope for the introduction of discrepancies
- be sufficiently intuitive and reduce the dependency on specialist knowledge
- embed key standards to help users produce compliant documentation more easily.
Figure 3 shows an example of an output from such an automated solution. The data in the diagram comes from a central database, and its placement is automatic. The user specifies certain basic parameters and can also change these parameters and obtain updated documents immediately.
Considering the example cited above of a small project with about 1,000 I/O, below is a comparison of the approximate time taken to produce design and engineering documents by an automated tool instead of methods using Excel, AutoCAD, and other conventional tools. With the automated solution, there is an upfront investment to define the project properties and parameters, specify the tag formats, create user roles and permissions, and create detailed records for all devices in the project.
In a well-designed automated solution, this is a one-time activity. Thereafter, generating any of the required project documents is instantaneous. Because of the centralization of data, there is far less work validating information across documents produced from the same centralized source of information.
In comparison, users applying conventional methods spend significant amounts of time generating and regenerating project documents as changes arise, as well as validating the information across these documents.
A well-designed automation solution can execute a project with 1,000 I/O with 60 percent less effort compared to using conventional methods. This saving grows as the I/O scope increases due to efficiencies in the automated process. Considering the potential to save time and cost while increasing quality, there is a strong case for using a standards-based automated solution to generate documentation in automation projects.
ReferencesISA-5.1-2009, Instrumentation Symbols and Identification
ISA-5.4-1991, Instrument Loop Diagrams
ISA-20-1981, Specification Forms for Process Measurement and Control Instruments, Primary Elements, and Control Valves
Commercially available tools
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