ISO 1219 Fluid Power Symbols — Hydraulic & Pneumatic Schematic Editor
ISO 1219 — Fluid power systems and components — Graphical symbols and circuit diagrams
ISO 1219 is the international standard that defines the graphical symbols used on hydraulic and pneumatic circuit diagrams. Part 1 (ISO 1219-1) specifies the individual symbols — for pumps and motors, linear actuators (cylinders), directional control valves, pressure and flow-control valves, conditioning equipment, accumulators, reservoirs, and instrumentation — together with the three line-type conventions (working-pressure, pilot/control, and drain) that establish the circuit topology. Part 2 (ISO 1219-2) addresses the rules for assembling those symbols into complete circuit diagrams, including component identification codes, cross-referencing between sheets, and title-block content.
Because ISO 1219 is the language of fluid power documentation, any hydraulic or pneumatic circuit diagram produced for procurement, maintenance, commissioning, or regulatory review is expected to conform to it. The MechanixCalc Fluid Power Schematic editor implements ISO 1219-1 directly: every symbol in its library is drawn to the geometry the standard specifies, the three line types are pre-coded as working, pilot and drain, and the exported PDF engineering report carries the ISO 1219-1 reference in the title block.
Calculators that implement ISO 1219
- Fluid Power Schematic EditorBrowser-based drag-and-drop editor with the full ISO 1219-1:2012 symbol library, three coded line types, auto-tagging, multi-sheet support, BOM, and PDF export.
- Hydraulic Cylinders CalculatorSize and verify the hydraulic cylinders placed in the schematic — extension force, retraction force, rod buckling safety factor, and cushioning analysis (ISO 6020 / ISO 6022).
- Hydraulic Accumulator CalculatorSize the accumulator shown in the circuit — nitrogen precharge, required gas volume, isothermal or adiabatic gas law, and PED 2014/68/EU compliance check (EN 14359).
- Pneumatics CalculatorCalculate cylinder bore, advance and retract force, valve Cv/Kv and ISO 6358 sonic conductance for the pneumatic actuators and valves documented in the schematic.
What ISO 1219 covers
- Graphical symbols for energy conversion: fixed- and variable-displacement hydraulic and pneumatic pumps and motors, drawn as standardised circles with directional triangles indicating flow direction and displacement type (ISO 1219-1)
- Linear actuator symbols: single-acting and double-acting cylinders, with optional cushion and through-rod variants — the symbol geometry encodes the actuation logic unambiguously for any trained reader
- Directional control valve notation: the n/m shorthand (n ports / m positions) with valve-position boxes showing internal flow-path arrows, and standardised actuation symbols (spring, solenoid, pilot, manual lever, pedal) appended to each box end
- Pressure- and flow-control valve symbols: relief valves (normally-closed, spring-loaded, ported to tank), pressure-reducing valves, sequence valves, check valves, and pressure-compensated flow-control valves — each drawn with a distinctive ISO 1219-1 geometry
- Conditioning and storage equipment: filters, water separators, heat exchangers, accumulators (bladder, piston, diaphragm), reservoirs (vented and pressurised), and instrumentation symbols (pressure gauges, flow meters, temperature sensors)
- Circuit-diagram rules (ISO 1219-2): component identification codes (e.g. M1, P1, DV1), connection and crossing conventions, off-sheet cross-reference arrows, title-block requirements including sheet number, revision, date, and the governing ISO 1219 reference
Parts of the standard
- ISO 1219-1Graphical symbols and circuit diagrams — Part 1: Graphical symbols for conventional use and data-processing applications
- ISO 1219-2Graphical symbols and circuit diagrams — Part 2: Circuit diagrams
Frequently asked questions
What is ISO 1219 used for?
ISO 1219 defines the graphical symbols and circuit-diagram rules used on hydraulic and pneumatic engineering drawings. Part 1 specifies each individual symbol — pumps, motors, cylinders, directional control valves, pressure and flow-control valves, accumulators, filters, reservoirs, and instrumentation — together with the three line-type conventions (working-pressure, pilot/control, and drain/case-return). Part 2 defines how to assemble those symbols into a complete, traceable circuit diagram with component identification codes and title-block requirements. Any hydraulic or pneumatic system drawing intended for procurement, installation, maintenance, or regulatory review is expected to conform to ISO 1219.
What does the 'n/m' valve notation mean (e.g. 4/3 valve)?
The ISO 1219 shorthand n_ports / n_positions describes a directional control valve's function in two numbers. The first number is the count of fluid connections on the valve body (typically 2, 3, or 4 — the pressure port P, tank port T, and actuator ports A and B). The second number is the count of discrete spool positions (typically 2 or 3). A 4/3 valve, for example, has 4 fluid ports and 3 spool positions — common for a spring-centred directional valve with two working positions and a blocked or float centre. The actuation method (solenoid, spring, pilot, lever) is shown as a standardised appendage on each end of the valve symbol.
What are the three ISO 1219 line types and when is each used?
ISO 1219-1 specifies three distinct line styles for the three classes of fluid path. Working-pressure lines (solid heavy lines) carry the main pressurised fluid between the pump, valves, and actuators — the power backbone of the circuit. Pilot and control lines (dashed) carry low-flow signals that actuate valve spools or sequence logic; they trace the control path independently of the main power flow. Drain and case-return lines (fine dotted) carry leakage and case-return fluid at low pressure back to the reservoir; they must never be back-pressurised. Using the correct line type makes circuit intent immediately readable to any ISO-trained engineer or technician.
How does ISO 1219-2 define component identification?
ISO 1219-2 assigns each component on the diagram a unique identification code built from a letter prefix that indicates the component type (P for pumps, M for motors, CV for check valves, DV for directional valves, RV for relief valves, A for accumulators, and so on) followed by a sequential number. This tagging scheme links the circuit diagram to the bill of materials, the parts list, the maintenance schedule, and any cross-references between sheets. The MechanixCalc schematic editor auto-generates ISO 1219-2-style tags when you place each symbol and exposes them in the BOM and CSV export.
Is the fluid power schematic editor free?
You can use the editor during a free 30-minute preview with no sign-up required. A free 14-day account trial (no credit card) unlocks every tool at Pro level, including unlimited sheets and cloud save. The branded PDF engineering report with an ISO 1219-1 title block, saved schematics, and share links are part of a paid Pro plan.
Run a ISO 1219 calculation on your own numbers
Free 30-minute preview — no sign-up. A free 14-day account trial unlocks every tool and the branded PDF report.
Open the Fluid Power Schematic Editor