This manual is designed for engineers and technicians from a wide range of abilities and backgrounds and will provide an excellent introduction to mastering plant documentation and diagrams. It covers the flow of documentation from design through manufacture to maintenance and operations.
The manual looks at the applications of each diagram type detailing where and when the document should be used. During the life span of any plant, a multitude of different vendors will supply plant modifications and equipment as the plant is continuously enhanced. The quality of the documentation produced will vary enormously with each new supplier. This manual will give you the skills to apply a standardized internationally acceptable set of standards to your plant documentation.
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An Overview - Best Practice in Process, Electrical & Instrumentation Drawings and Documentation
The objective of this course is to familiarize the participants with the various standards that apply to the production of plant drawings, diagrams and documentation. The topics contained in the course are of interest and relevance to all users of documentation whether they are designers of electrical installations, erection engineers or personnel responsible for operation and maintenance of the installations
Although many organizations have developed, over time, a range of “in-house” standards they all have a level of traceability to a set of international standards in order to facilitate clear communication of the requirements and operation of a particular plant design.
In this manual we will make direct reference to a range of commonly used standards which are either recognized internationally or are national standards with traceability to an international standard.
1.2 An overview of the contents of the manual
This manual commences with a broad overview of the role of a range of standards and their associated organizations and using these standards builds progressively a complete project documentation dossier of drawings, diagrams, lists, schedules etc. covering the Process, Instrumentation, Electrical and Electro-Pneumatic / Hydraulic needs of a plant. The manual concludes with a short section covering vendor interaction as all projects require, to a greater or lesser degree a level of documentation from equipment vendors.
It should be recognized that this dossier is by no means complete in the sense that specific projects will often require additional special documents but often these can be adapted from one of the templates contained in this manual.
1.3 What are standards and why are they necessary?
Standards are documented agreements containing technical specifications or other precise criteria to be used consistently as rules, guidelines, or definitions of characteristics, to ensure that materials, products, processes and services are fit for their purpose.
For example, the format of the credit cards, phone cards, and "smart" cards that have become commonplace is derived from an ISO International Standard. Adhering to the standard, which defines such features as an optimal thickness (0.76 mm), means that the cards can be used worldwide.
International Standards thus contribute to making life simpler, and to increasing the reliability and effectiveness of the goods and services, we use.
Standards for documentation, equipment, appliances, and devices of an installation are necessary for the following reasons.
1.3.1 So who sets the standards?
ISO – International Standards Organization
What is ISO?
The International Organization for Standardization (ISO) is a worldwide federation of national standards bodies from more than 140 countries, one from each country.
ISO is a non-governmental organization established in 1947. The mission of ISO is to promote the development of standardization and related activities in the world with a view to facilitating the international exchange of goods and services, and to developing cooperation in the spheres of intellectual, scientific, technological and economic activity.
ISO's work results in international agreements, which are published as International Standards.
Many people will have noticed a seeming lack of correspondence between the official title when used in full, International Organization for Standardization, and the short form, ISO. Shouldn't the acronym be "IOS"? Yes, if it were an acronym – which it is not.
In fact, "ISO" is a word, derived from the Greek isos, meaning "equal", which is the root of the prefix "iso-" that occurs in a host of terms, such as "isometric" (of equal measure or dimensions) and "isonomy" (equality of laws, or of people before the law).
From "equal" to "standard", the line of thinking that led to the choice of "ISO" as the name of the organization is easy to follow. In addition, the name ISO is used around the world to denote the organization, thus avoiding the plethora of acronyms resulting from the translation of "International Organization for Standardization" into the different national languages of members, e.g. IOS in English, OIN in French (from Organization internationale de Normalization). Whatever the country, the short form of the Organization's name is always ISO.
How it all started
International standardization began in the electrotechnical field: the International Electrotechnical Commission (IEC) was created in 1906. Pioneering work in other fields was carried out by the International Federation of the National Standardizing Associations (ISA), which was set up in 1926. The emphasis within ISA was laid heavily on mechanical engineering.
ISA's activities ceased in 1942, because of the Second World War. Following a meeting in London in 1946, delegates from 25 countries decided to create a new international organization "the object of which would be to facilitate the international coordination and unification of industrial standards". The new organization, ISO, began to function officially on 23 February 1947.
The first ISO standard was published in 1951 with the title, "Standard reference temperature for industrial length measurement".
SI – System International
The creation of the decimal Metric System at the time of the French Revolution and the subsequent deposition of two standards representing the meter and the kilogram, on 22 June 1799, in the Archives de la République in Paris can be seen as the first step in the development of the present International System of Units.
IEC – International Electrotechnical Commission
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes international standards for all electrical, electronic and related technologies. These serve as a basis for national standardization and as references when drafting international tenders and contracts.
Through its member, the IEC promotes international cooperation on all questions of electrotechnical standardization and related matters, such as the assessment of conformity to standards, in the fields of electricity, electronics and related technologies.
The IEC charter embraces all electrotechnologies including electronics, magnetics and electromagnetics, electroacoustics, multimedia, telecommunication, and energy production and distribution, as well as associated general disciplines such as terminology and symbols, electromagnetic compatibility, measurement and performance, dependability, design and development, safety and the environment.
The Commission's objectives are to:
IEC's international standards facilitate world trade by removing technical barriers to trade, leading to new markets and economic growth. Put simply, a component or system manufactured to IEC standards and manufactured in country A can be sold and used in countries B through to Z.
IEC's standards are vital since they also represent the core of the World Trade Organization's Agreement on Technical Barriers to Trade (TBT), whose 100-plus central government members explicitly recognize that international standards play a critical role in improving industrial efficiency and developing world trade. The number of standardization bodies which have accepted the Code of Good Practice for the Preparation, Adoption and Application of Standards presented in Annex 3 to the WTO's TBT Agreement underlines the global importance and reach of this accord.
IEC standards provide industry and users with the framework for economies of design, greater product and service quality, more inter-operability, and better production and delivery efficiency.
At the same time, IEC's standards also encourage an improved quality of life by contributing to safety, human health and the protection of the environment.
The IEC's multilateral conformity assessment schemes, based on its international standards, are truly global in concept and practice, reducing trade barriers caused by different certification criteria in various countries and helping industry to open up new markets. Removing the significant delays and costs of multiple testing and approval allows industry to be faster and cheaper to market with its products.
As technology becomes more complex, users and consumers are becoming more aware of their dependence on products whose design and construction they may not understand. In this situation, reassurance is needed that the product is reliable and will meet expectations in terms of performance, safety, durability and other criteria.
How can the industrial user and the final consumer be sure that the product they buy conforms to the criteria of an IEC standard? The IEC's conformity assessment and product certification schemes exist to provide just this reassurance, and the regulatory nature of some products now also sees recognition of the CA schemes amongst some government regulators.
On 15 September 1904, delegates to the International Electrical Congress, being held in St. Louis, USA, adopted a report that included the following words:
"…steps should be taken to secure the co-operation of the technical societies of the world, by the appointment of a representative Commission to consider the question of the standardization of the nomenclature and ratings of electrical apparatus and machinery."
As a result, the IEC was officially founded in June 1906, in London, England, where its Central Office was set up.
By 1914, the IEC had formed four technical committees to deal with Nomenclature, Symbols, Rating of Electrical Machinery, and Prime Movers. The Commission had also issued a first list of terms and definitions covering electrical machinery and apparatus, a list of international letter symbols for quantities and signs for names of units, an international standard for resistance for copper, a list of definitions in connection with hydraulic turbines, and a number of definitions and recommendations relating to rotating machines and transformers.
The First World War interrupted IEC work, which resumed in 1919 and by 1923 the number of technical committees had increased to 10. IEC Council decided to create the Committee of Action "to assist in giving effect to the decisions of the Council, to second the efforts of the Central Office and to co-ordinate the work of the National Committees and of the Advisory Committees."
In 1930, the IEC established the following electrical units:
It was decided to extend the existing series of practical units into a comprehensive system of physical units, which became the "Giorgi system", named after Giovanni Giorgi (1871-1950) - an Italian scientist and engineer. This system has been elaborated further and is now commonly known as the "Système international", or SI for short.
Between the First and the Second World Wars, a number of new international organizations came into being and the IEC recognized the need for co-operation to avoid overlapping efforts. In some cases, joint technical committees were formed, such as the International Special Committee on Radio Interference (CISPR).
In 1938 the IEC produced the first edition of the International Eletrotechnical Vocabulary (IEV). The unification of electrotechnical terminology was one of the principal tasks allocated to the IEC by the St. Louis congress. In the early days, the Nomenclature Committee was engaged in pioneer work, as no comparable international technical vocabulary had yet been published and few national electrotechnical vocabularies existed. With its 2000 terms in French, English German, Italian, Spanish and Esperanto, and its definitions in French and English, the IEV could rightly be considered as an outstanding achievement. It aroused wide interest among international technical organizations outside the electrotechnical field.
In September 1939, the IEC's activity came to a standstill because of the Second World War and did not resume for another six years.
In 1948, the IEC Central Office moved from London to Geneva, Switzerland. Subsequently, the IEC expanded its efforts in the light current field, which had constituted only a small part of the activity of the Commission before 1939. Standards covering measurements, safety requirements and the testing and specification of components for radio receivers and televisions began to appear. At the same time, work on electroacoustics started, while CISPR developed standards on permissible limits for various frequency ranges used for radio broadcasting and measurement methods for interference.
From 1948 to 1980, the number of technical committees grew from 34 to 80 and began to include such new technologies as capacitors and resistors, semiconductor devices, electrical equipment in medical practice and maritime navigation and radio communication systems and equipment.
ISA – Instrument Society of America
History of ISA – the instrumentation, systems, and automation society
Industrial instruments, which became widely used during World War II, continued to play an ever-greater role in the expansion of technology after the war. Individuals like Rimbach and others involved in industry saw a need for the sharing of information about instruments on a national basis, as well as for standards and uniformity. The Instrument Society of America addressed that need with more than 39,000 members from more than 110 countries.
Recognizing ISA’s international reach and the fact that its technical scope had grown beyond instruments, in the fall of 2000, the ISA Council of Society Delegates approved a legal name change to ISA–The Instrumentation, Systems, and Automation Society.
The founders’ mission
The object of the Society shall be to advance the arts and sciences connected with the theory, design, manufacture, and use of instruments in the various sciences and technologies.
The mission of ISA as the global society for instrumentation, systems, and automation is to:
ASME – American Society of Mechanical Engineers
As with many other standards, the dominance of a particular institution or society, and the broad international acceptance of its publications often lead to a de facto recognition of certain publications as an international standard. As with ISA above ASME produces a wide range of standards relevant to best drawing practices and these publications (ASA’s) are referenced later in this manual.
1.4 Drawing office operating standards
1.4.1 Drawing office operating manual
In any given plant therefore the drawing office must establish what standards it is going to employ and what processes it will utilize to control the quality, workflow and ultimately the archiving of its output. As many drawing offices may use contract staff to undertake significant projects it is important that a clear and uniform set of rules be documented to cover all activities. The Drawing Office operating manual satisfies this need and a typical manual should address the following elements.
1.4.2 Drawing office organizational structure
The drawing office is a subset of the design office and as such the overall authority resides with the Resident Engineer or the Project Manager. His requirements and decisions are passed to the drawing office staff via the Chief Draughtsman and/or discipline specific Engineers.
1.4.3 Office discipline
Administration personnel involved
Time keeping and office discipline is the responsibility of the Chief Draughtsman.
Time books showing a log of all hours need to be maintained by the Chief Draughtsman. All staff shall submit a weekly timesheet to the Chief Draughtsman for approval before it is passed to accounts for payment and/or client billing purposes.
Quality and quantity of the work produced by the drawing office shall be monitored by the Chief Draughtsman.
Should any contentious points arise concerning either discipline or personal problems which cannot be solved between the relevant personnel they may be brought to the attention of the Chief Draughtsman and ultimately the Resident Engineer.
1.4.4 Methods of work initiation, control and reporting
No work should commence without a work request carrying the requisite information and signatures.
The following information should be completed before commencement of work:
Should the work request refer to an existing structure, i.e. in the case of an extension or require a new structure based on a previous job, it is imperative that site investigations be carried out before work is commenced as modifications may have been made on site.
On completion of the job the original work request should be filed with the project documentation package and kept as a permanent record.
Program progress reports
The Chief Draughtsman is responsible for scheduling and allocating work in an endeavor to meet the Project time schedule consistent with available manpower.
1.4.5 Draughting procedures
The function of the Design Office is to provide and communicate information to the end user in drawing form. Clear, easy to read and understandable drawings that transmit the necessary information are therefore the prime objectives.
The intent of the following section is to provide uniform information and typical details that serve as a guide and help in our work.
When making a Drawing
Standards and specifications
Functional draughting is not a set of hard and fast rules. They are principles that are to be followed in making drawings. Particulars and their application in specific cases will be left to the draughtsman’s judgment and good sense backed by their experience and knowledge of a given project’s requirements.
Plan your drawing
A drawing must be simple yet clear and sufficient. A drawing should not just grow, it must be planned. Think through the drawing before you lay it out. Have a clear idea what has to be communicated and then decide on the best way to communicate the idea. A good clear drawing should be produced from left to right and from top to bottom and not be just a random distribution of details and views fitted in wherever there happens to be space for them.
A drawing is not a picture; it is a diagrammatic representation of the object. Any unnecessary line is a waste of time: Eliminate unnecessary elaboration that adds nothing to the message. Shading, etc. falls into this category with few exceptions.
Repetition of typical details
Once a typical detail has been identified -stop. If ten off are required -draw the one detail only and indicate by a note or instruction that there are ten off required. If this typical detail is required on other drawings for the project then all that is needed is a reference to the original key drawing with the typical detail - do not redraw the detail.
It is important to establish the existence of an obvious pattern. Once sufficient draughting is done to establish this pattern clearly, stop delineating and give a note or instruction.
Eliminate unnecessary views
Always question the necessity of a projected view. A description, a note or a reference may be all that is required. Guard against re-drawing an entire item in another projection just for the sake of showing a minor divergent detail, or a secondary view which does not show anything but a diameter or a thickness.
Pretty much all of us live in a metric world. All drawings should be scaled to standard metric size sheets (in CAD software) or prepared on standard metric plastic drawing sheets.
All sheets should use pre-configured templates with title blocks, borders, etc. (for CAD software) or pre-printed equivalents when using plastic drawing sheets.
Where possible a constant set of scales shall be used on one set of drawings. This can help considerably in checking out obstructions between disciplines by a simple overlay. In addition, the eye becomes accustomed to viewing the drawing in perspective.
Avoid using “odd” scales, e.g. 1:25, 1:30, 1:175, etc. as in future someone else may work on these drawings. Try to use only common scales e.g. 1:200, 1:100’ 1:50, 1:20, 1:10, 1:5.
For hard drawings, plastic leads or ink may be used. For CAD based drawings layering should be used with all detail in black.
Lettering sizes and styles for different sheets sizes should be defined.
Titles of drawings
In general the drawing title will be presented in a three-sequence format after the initial box-designating client name:
1.4.6 General information on drawings
Cross-reference and information traceability
It is of utmost importance that the information shown on a drawing be cross-referenced such that the source is fully traceable and other project drawings that are directly affected by this information are identified. It is therefore critical that each drawing used as a source of information in the preparation of your current drawing be noted as a reference drawing in the current drawing reference block provided.
There are three main cases where the use of a key plan is necessary:
First angle / Third angle projections
Projection is a means to represent a three dimensional attribute of an object on one or more planes. A company standard convention should be defined such that all projection drawings are either 1st Angle (European) or 3rd Angle (American). The projection type must always be shown on the drawing.
The location and utilizing of existing information is critical in the production of drawings. Do not re-invent the wheel.
Catalogued reference system
A comprehensive catalogued reference system should be maintained in the Drawing Office Filing Section. This system references and correlates all drawings to projects, types of plant, structures, buildings and related manufacturer’s items. This system should be available to all personnel.
The reference system may consist of:
Manufacturers provide a vast source of catalogued information which is readily available on request. A good library is an invaluable resource in ensuring that the draughtsmen utilize readily available materials rather than custom manufactured items in so far as possible. Maintaining this library and keeping it up to date with a formalized system of review is an inherent part of the overall operation of a drawing office.
Alternative source of information
If having exhausted the Drawing Registers, catalogues, etc, the draughtsman still lacks information ASK. There is often available (to all draughtsmen) a senior person with specialized knowledge and many years experience and this should be utilized to the full.
Information - responsibility and accuracy
The Engineer is responsible for the aesthetic, schematic and detailed design of any plant, equipment or structure. He will be involved in the conceptual layout of any given scheme to ensure suitability for duty, safety of operation and code compliance. He must also sign the Approval Drawing.
The Chief Draughtsman and Draughtsman are responsible for the accurate representation of all information on the drawings.
Drawing distribution procedures
A formalized system of drawing approvals must be implemented in any drawing office to define the stage / status of a drawing – the following gives some suggestions as to how this process can be accommodated.
1.4.7 Issued for approval
Approval drawings are required mainly for layouts but may be used for any drawing where specific items are required to be drawn to the Engineer’s attention. An approval drawing need not be complete or fully dimensioned, but must clearly define the concept.
The approval drawing is a scheme, which requires approval from the Engineer. These drawings are not to be issued for Tender, Construction or to any Consultant or Contractor to use as final drawings.
After approval of a drawing with all appropriate signatures the drawings need not be re-issued for final approval unless specifically requested on the approval form.
1.4.8 Issued for final approval
On completion of final drawings and prior to issue, a print shall be made and this shall be handed over to the Project Engineer for his signature and to record that final drawings have been issued to his approval, all previous comments having been acted on to his satisfaction. This shall not be used for further modifications.
1.4.9 Issued for information only
There are a number of situations where a drawing may be issued for information only, i.e. these drawings may be worked to for manufacture or construction.
1.4.10 Issued for tender
1.4.11 Issued for manufacture or construction
1.4.12 As built
Checking procedures fall directly under the control of the Chief Draughtsman.
The Checking activity is the “last line of defense” in the system to ensure that a drawing represents as closely as possible the functional requirements of the job. As such, the checker needs to critically analyze and question any proposal put forward.
The Checker has the right and may challenge, without prejudice, any idea, concept or formulation that has been committed to paper.
The Checker shall not subscribe to any suggestion until the Checker is totally convinced of its usefulness and fitness for purpose.
No drawing shall be issued for manufacture unless it is authorized by a Checker.
The checking procedure entails a methodical step-by-step study of all phases of the design of a given item in relation to the function it performs. The philosophy underlying this approach is not concerned with appraisal of any given part per se. Rather the appraisal focuses on the function, which the part, or the larger assembly containing the part, performs. This approach is designed to lead the analyst away from a traditional perspective which views a part as having certain accepted characteristics and configurations. Indeed, it encourages the analyst to adopt a broader point of view and to consider whether the part will perform the required function as efficiently and as inexpensively as possible.
1.4.14 The checklist
It is useful to develop a checklist to systemize the checking activity. The following is a general checklist, which should be supplemented by more specific items from the checkers.
Determine the function of the item then establish:
1.4.15 Dimensional accuracy
This is of crucial importance. Dimensions must be checked on a local and overall basis. Particular attention must be given to mating parts, e.g. base plates, foundations, etc.
The orientation of each element must be checked in relation to the total unit. In this respect, an orientation diagram must be included on the drawing showing the relevant position of the item in question.
1.4.16 Checking procedures
A suggested color code for checking
1.4.17 Printing and filing
Printing and filing activities need to be defined in a drawing office to ensure the highest level of efficiency together with the best utilization of available printing equipment.
Printing of all drawings
Printing requirements normally fall into three categories:
Registering of drawings
Filing of all drawings
Records of all expenses on office supplies
It is the responsibility of the Chief Draughtsman to keep accurate records of all stationery ordered.
Issuing and dispatching of drawings
All drawings issued through the Drawing Office / Printing Section must be formally requested. This may be done by way of an official issue slip or drawings being for tender or construction. All drawings issued should be accompanied by a document transmittal form which should be signed and returned and filed by the originator for record purposes.
Binding of documents
Where required the parties responsible for printing the documents may be called upon to make up a package of documents required for tender purposes. Again, explicit instructions shall be given as to the number required and the content therein.
1.5 General drawing standards
Although we acknowledge that a large number of mature organizations have adapted a range of standards to suit their particular needs it is appropriate in this manual to provide recommendations with direct traceability to an international set of rules. The following recommendations are therefore taken from AS 1100.101-1992 Technical Drawing –General Principles – the Australian Standard for Technical Drawing.
This standard is in agreement with the following International Standards.
ISO 128 Technical Drawings – General Principles of Presentation
ISO 129 Technical Drawings – Dimensioning
ISO 406 Technical Drawings – Tolerancing of linear and angular dimensions
ISO 1101 Technical Drawings – Geometrical Tolerancing
ISO 1660 Technical Drawings – Profile Dimensioning
ISO 3040 Technical Drawings – Cone Dimensioning
ISO 3098/1 Technical Drawings – Lettering
ISO 5455 Technical Drawings – Scales
ISO 5459 Technical Drawings – Datum Systems for Geometric Tolerancing
ISO 6410 Technical Drawings - Representation of Threaded Parts
1.5.2 Size of drawing sheets
The preferred size of drawing sheets is taken from the ISO-A series which is listed in the table below.
Trimmed size (mm)
Width of border (mm)
841 × 1189
594 × 841
420 × 594
297 × 420
210 × 297
Non-preferred sizes and roll drawings
Under certain circumstances the use of other drawing sheet sizes may be necessary and the ISO-B series sheets may be used. Roll drawings when required should have standard widths of either 860mm or 610mm.
1.5.3 Thickness of format lines
Recommended line thicknesses in mm for format lines are per the table below.
A2, 3, 4 Sheet
Title Block Lines
Other Format Lines
1.5.4 Thickness of drawing lines
The thickness of drawing lines is covered in detail in the standards and is based on line group types which may be 1.0, 0.7 & 0.5 mm (line group 1.0 mm typically used on A0 sheet sizes) through to 0.35, 0.25 & 0.18 mm (line group 0.35 mm which may be more appropriate for A4 sheets). The standard specifically states that the minimum line thickness on a drawing after reproduction (including reduction) should not be less than 0.18 mm.
1.5.5 Text types and character heights
The following text types are provided for in the drawing standards.
The height of the characters should be one of the following (in mm) with minimum character line thickness not less than 10% of the height
The height of the characters should not be less than 1.7 mm on a reduced drawing reproduction.
1.5.6 Ratio of text size to corresponding line thickness
The ration of line thickness to text size is generally 1:10 and one of the following sets of standard text sizes and corresponding line thickness’ is often used. Note that although Set 2 does not strictly meet the Australian Drawing Standard it is often referenced in other standards – the attached tables reference to the South Africa standard (SABS 0111 1990).
1.5.7 Title block
Title block layouts are normally laid out as standard templates with unique logos pertaining to the individual company. The standards cover a variety of designs with dimensions for different sheet sizes but specific layout is not dictated. As a general rule however the title block should be located in the bottom right hand corner of the drawing sheet or when this restricts the drawing layout the top right hand corner may be used.
As a minimum however the Title block contains the following:-
Other information of relevance may include:
1.5.8 Reference drawings
1.5.9 Recommended sheet sizes versus drawing types
As stated previously many companies have established in-house standards regarding a variety of drawing areas not covered by ISO standards. A typical recommendation of drawing sheet size versus drawing type is as per below. Bear in mind the reduction of drawing size when reproducing large drawings must not allow the line thicknesses or character heights to fall below the values stated in the standards for legibility. Reductions of more than 2 drawing sizes will in nearly all cases make portion of a drawing illegible.
Documentation type Drawing size
Piping & Instrumentation Diagrams A1
Process Flow Diagrams A1
Metering & Instrumentation
Instrument Schedules A4
Instrument Data Sheets A4
Instrument Hookup Diagrams A4
Loop Drawings A4
Panel Wiring Diagrams A1/A4
Cable Schedules A1/A4
Cable Block Diagrams A1
Cable Interconnection Diagrams A1
Plant I/O Schedules A4
Flow Charts A4
Software Listings A4
Single Line Diagrams A1/A4
Electrical Schematic & Wiring Diagrams A1
Cable Schedules A1/A4
Cable Block Diagrams A1
Cable Interconnection Diagrams A1