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ASME Y15.3M-1979 — Process Charts
📈 ASME Y15.3M-1979 (approved as American National Standard ANSI Y15.3M-1979) defines process charts, the charting procedure, and the principles and practices for their construction. It is the successor to ANSI Y15.3-1974 (ASME Standard 101-1972), “Operation and Flow Process Charts,” produced by the ASME Special Committee on the Standardization of Therbligs, Process Charts, and Their Symbols. That body of work is rooted in the concepts originated and developed by Dr. Frank B. and Dr. Lillian M. Gilbreth — including the definition, scope, and symbols of pure motions and their corresponding charting and analysis forms. In 1978 the ASME committee was reorganized and redesignated Subcommittee 3, Process Charts, of the American National Standards Committee Y15; this revision was approved by ANSI on December 17, 1979. In preparing it, the Committee avoided fundamental definitional and conceptual changes contrary to actual industrial practice and dropped only obsolete material while adding new charts and drawings.
💡 Process charts provide a systematic description of a process or work cycle involving the activities of humans, agents, or objects. Because a common medium of expression is used, a single process chart serves the needs of many people either performing, managing, or analyzing the work — analysis, methods improvement, job instructions, and training are the most frequent uses.
1. Scope: What a Process Chart Is 📌
Chapter 1 defines a process chart as a schematic or tabular representation of the sequence of all relevant actions or events — operations, transportations, inspections, delays, storages, and the like — occurring during a process or procedure, including information desirable for analysis such as time required and distance moved. Two types are used:
- Material type: presents the process in terms of the events that occur to the material(s) being processed.
- Person type: presents the process in terms of the activities of the person(s) performing the steps of the process.
For analytical purposes and to aid in detecting and eliminating inefficiencies, the Standard classifies the actions occurring during a given process into five activities — operations, transportations, inspections, delays, and storages — each with a standard symbol. The symbols and forms illustrated in the Standard represent current definitions and concepts drawn from industry, so the chart speaks a common language.
2. The Five Activities and Their Standard Symbols 🔤
| Activity | Symbol | Definition | Typical Examples |
|---|---|---|---|
| Operation | Circle ◯ | An object is intentionally changed in any physical or chemical characteristic, assembled or disassembled, or arranged/prepared for a following step; also when information is given or received or when planning or calculating takes place | Drilling, heat treat, assembly, keying, computing |
| Transportation | Arrow → | An object is moved or a person moves from one location to another, except movement that is part of an operation or caused by the operator at the work station | Trucking, conveyor, walking |
| Inspection | Square □ | An object is examined for identification or verified for quality or quantity in any of its characteristics | Visual check, gauging, counting, lab test |
| Delay | Letter D | An object or person waits for the next planned action | Waiting in queue, paperwork awaiting approval |
| Storage | Inverted triangle ▽ | An object is kept and protected against unauthorized removal | Warehouse, finished-goods storage |
⚠️ A note on Gilbreth vs. this Standard: the Gilbreths used a small circle for transportation (which violates clarity criteria 2 and 5) and a double triangle, one inside the other, for temporary storage. The Standard adopts an arrow and a single inverted triangle instead, so always follow the symbol set of this Standard to avoid ambiguity.
3. Combined and Modified Symbols ✏️
Progress in diagramming office work, data processing, materials handling, and warehouse operations created situations where it is desirable to vary or combine the basic symbols. The Standard gives two documented examples:
- Encircled circle: a modified Operation symbol indicating the creation of a record or a set of papers in paperwork applications.
- Shaded circle: a modified Operation symbol indicating the addition of information to an existing record or set of papers.
These modified symbols keep the conceptual framework of the five basic activities intact while making clerical actions precise — a standardized extension of the process chart from the shop floor into the office and data-processing domains.
4. Construction Principles and Chart Forms 🛠️
Chapter 2 sets out the principles and practices for constructing process charts (identification in 2.1; major conventions for schematic charts on plain paper in 2.2; other schematic conventions in 2.3; major conventions for tabular charts on prepared forms in 2.4; the summary form in 2.5; conclusion in 2.6–2.7), supported by worked figures:
- Schematic charts (plain paper): a typical operation process chart; a material-type flow process chart showing how several components are processed and brought together; a planned material flow (a chart form without conventional symbols); and a chart from raw material to finished product.
- Tabular charts (prepared forms): person-type flow process charts using preprinted symbols and analysis-action columns for both the present and the proposed method, plus a chart showing present and proposed methods side by side with a summary of cost savings.
- Summary form: aggregates the counts, times, and distances of the five activities so present-vs-proposed comparisons quantify the savings, giving decisions a firm factual base.
✅ A good process chart is symbolically consistent, complete in sequence, and rich in time and distance data, and it serves performers, managers, and analysts alike. After drawing, self-check that all five activity classes are covered and that no waiting or movement step was skipped.
5. Engineering Practice Essentials 🏭
- 🔍 Choose the chart type first: material type suits multi-component assembly and warehousing analysis; person type suits office procedures and operator-activity studies.
- 📐 Record quantitative data: annotate each step with time required and distance moved — the raw material for spotting bottlenecks and eliminating waste such as excess transportation and long delays.
- 🔄 Present method → proposed method: chart the current method honestly, then chart the proposed method, and compare activity counts, times, and distances in the summary form to document real savings.
- 🏷️ Complete the identification: fill in title, subject, method, date, and preparer per para. 2.1 so the chart remains traceable and reusable.
- 📚 Deploy for instruction: process charts double as job instructions and training aids; symbol consistency directly governs how well they are understood and followed.
6. Frequently Asked Questions ❓
❓ Q: How do I draw the line between operation, inspection, and transportation?
A: Ask what happens to the object: an intentional change in its physical or chemical characteristics, an assembly/disassembly, or preparation for a following step is an operation; verifying quality or quantity is an inspection; a change of location is a transportation (unless it is part of the operation).
A: Ask what happens to the object: an intentional change in its physical or chemical characteristics, an assembly/disassembly, or preparation for a following step is an operation; verifying quality or quantity is an inspection; a change of location is a transportation (unless it is part of the operation).
❓ Q: Can material-type and person-type charts be mixed?
A: The Standard defines them as two distinct types — one follows the events occurring to the material, the other the activities of the people performing the steps. Choose the type that matches the object of study and avoid mixing the two threads in one chart.
A: The Standard defines them as two distinct types — one follows the events occurring to the material, the other the activities of the people performing the steps. Choose the type that matches the object of study and avoid mixing the two threads in one chart.
❓ Q: Why did the Standard change the Gilbreth symbols for transportation and delay?
A: The Gilbreths’ small circle for transportation is easily confused with the operation circle, and the double triangle for temporary storage is cumbersome. The Standard adopts an arrow and a single inverted triangle, keeping the five-activity concept intact while satisfying symbol-clarity criteria.
A: The Gilbreths’ small circle for transportation is easily confused with the operation circle, and the double triangle for temporary storage is cumbersome. The Standard adopts an arrow and a single inverted triangle, keeping the five-activity concept intact while satisfying symbol-clarity criteria.
🔍 Q: What is the summary form used for?
A: It concentrates the count, time, and distance of each of the five activities and presents the present-method vs. proposed-method comparison with the cost savings — a standardized vehicle for reporting methods-improvement results to management and supporting decisions, as recommended in para. 2.5.
A: It concentrates the count, time, and distance of each of the five activities and presents the present-method vs. proposed-method comparison with the cost savings — a standardized vehicle for reporting methods-improvement results to management and supporting decisions, as recommended in para. 2.5.
