Overview
ISO 561:1989 - Coal preparation plant - Graphical symbols defines a basic, internationally consistent set of graphical symbols for use on flowsheets and process diagrams for coal preparation plants. The standard selects symbols according to clear principles: they should represent widely used plant items, be easy to draw, be readily distinguishable from one another, indicate the principle of operation (not the exact appearance), and remain distinguishable from nationally standardized symbols when a single ISO symbol covers a group of related items.
Key topics and requirements
- Scope: Symbols are intended for flowsheets and other diagrams related to coal preparation plants (see ISO 924 for flowsheet conventions).
- Selection principles: Symbols must be commonly used, simple to draw, distinguishable, and represent functional principles rather than specific machine models.
- Drawing conventions:
- Plant symbols shown with thick lines; product flow shown with fine lines.
- Flowlines generally enter symbols from the top or left and leave downward or to the right.
- Multiple inlet/outlet streams are represented by varying numbers of entry/exit arrows.
- Symbol coverage: The standard provides basic symbols and an alphabetical index covering common coal-preparation equipment such as conveyors, crushers, screens, classifiers, cyclones, thickeners, flotation cells, filters, centrifuges, pumps, fans, feeders, stockpiles and reclaimers, magnetic separators, jigging and washing units, dryers and mixers.
- Interoperability: Where process control symbols are needed, ISO 561 refers to the ISO 3511 series for instrumentation and control symbolic representation.
Applications and who uses it
ISO 561:1989 is used to standardize visual communication in the coal-processing sector and is valuable for:
- Process engineers and plant designers preparing flowsheets and process diagrams
- Draftsmen and CAD technicians creating engineering drawings
- Equipment manufacturers and suppliers providing documentation and factory drawings
- Plant operators, maintenance teams and technical authors who rely on consistent diagrams for training, operation and troubleshooting
- Standards bodies and consultants ensuring compatibility across international projects
Using ISO 561:1989 improves clarity, reduces misinterpretation in design and handover, and streamlines cross-border collaboration on coal preparation plant projects.
Related standards
- ISO 924 - Coal preparation plant: Principles and conventions for flowsheets
- ISO 3511-1, ISO 3511-2, ISO 3511-3 - Process measurement, control functions and instrumentation: symbolic representation (basic and detailed symbols)
Keywords: ISO 561:1989, coal preparation plant, graphical symbols, flowsheets, process diagrams, conveyors, screens, cyclones, flotation, filters, ISO 924, ISO 3511.