Hydraulic Cylinder Symbol

Definition: The Hydraulic Cylinder symbol represents a linear actuator that converts hydraulic pressure into straight-line force and motion, drawn per ISO 1219-1 as a long rectangle (the barrel) containing a piston line with a rod extending through one end, with two ports — Cap End (blind/piston side) and Rod End (annulus side) — for a double-acting unit.

Also known as: hydraulic ram, double-acting cylinder, linear actuator (hydraulic), hydraulic jack cylinder, tie-rod cylinder, welded cylinder, actuating cylinder.

What the Hydraulic Cylinder symbol means

The Hydraulic Cylinder symbol denotes the most common hydraulic actuator: pressurising the Cap End port pushes the piston and extends the rod; pressurising the Rod End port retracts it. The symbol's two ports declare it double-acting — powered in both directions — as opposed to a single-acting cylinder (one port, returned by spring or load, the spring drawn inside the barrel). The geometry drawn in the symbol encodes the physics: the rod occupies part of the piston area on the rod side, so the annulus area is smaller than the full bore area.

That area difference is the key to reading any cylinder circuit. Extension delivers more force but moves slower for a given flow; retraction is faster but weaker. It also creates the differential-flow effect: while extending, the rod end discharges less fluid than the cap end receives, and while retracting the cap end discharges more than the rod end receives — which matters for valve sizing and enables regeneration circuits that route rod-end discharge back into the cap end for fast advance. Force is simply pressure times effective area (F = p × A), so a 100 mm bore at 210 bar develops about 165 kN (≈16.8 tonnes) extending.

How to identify the Hydraulic Cylinder symbol

The symbol is an elongated rectangle with a vertical line inside (the piston) and a rod line extending through one end cap; port stubs connect at each end — Cap End at the blind end, Rod End near the rod. ISO 1219-1 modifiers extend the base form: a spring inside marks single-acting spring-return; arrows or slanted lines at the piston mark cushioning (adjustable cushions carry a small diagonal arrow); a rod at both ends is a double-rod cylinder; nested rectangles indicate a telescopic cylinder.

The pneumatic cylinder symbol is drawn identically — the medium is established by the rest of the circuit (energy-triangle fill on the pump/compressor, ISO 1219 sheet conventions) rather than the cylinder itself. As with all fluid power symbols, there is no competing ANSI shape in modern use: legacy ANSI Y32.10 matched this grammar and current North American drawings follow ISO 1219-1. NFPA T3.6 / ISO 6020/6022 govern the physical mounting dimensions, not the symbol.

Live editor identity: Live-library identity: `hydraulic-cylinder`, 80 × 30 canvas units, 2 logical terminals. Match this exact SVG and terminal list when identifying the placeable editor symbol; do not identify a physical package from the schematic outline alone.

Function and usage boundary

Fluid from the directional control valve enters the Cap End; pressure acting on the full piston area generates force, the piston advances, and fluid on the rod side exits the Rod End port back through the valve to tank. Reversing the valve swaps supply and return, and the annulus area drives retraction. Seals on the piston separate the two volumes; rod seals and a wiper keep fluid in and contamination out. End cushions — tapered spears entering pockets near each end cap — decelerate the piston over the last few centimetres to prevent hammering at full stroke.

Circuit reading around the cylinder is mostly about controlling gravity and speed: counterbalance valves hold suspended loads against creep and hose failure, pilot-operated check valves lock a cylinder mid-stroke, flow controls (meter-in or meter-out) set speed, and pressure-reducing valves limit clamping force. Long, slender cylinders in compression are checked for rod buckling; oversized bores are avoided because force rises with area but so do fluid consumption and cost.

Usage boundary: Use the Hydraulic Cylinder abstraction only when the intended circuit can be expressed through these logical ports: `cap` (Cap End), `rod` (Rod End). Select a versioned physical profile and exact manufacturer datasheet before assigning package pins, ratings, or fabrication dimensions.

Standards: IEC vs ANSI

The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.

Variant availability

• Editor implementation (available): This is the exact SVG and terminal geometry placed by the CircuitDiagramMaker editor.
• IEC 60617 (reference only): IEC 60617 is the official international source. This page does not present the editor SVG as a licensed or certified IEC reproduction.
• ANSI/IEEE 315 (reference only): IEEE 315 is the North American reference listed by IEEE as inactive-reserved; use the edition required by the project.

Logical terminals

The live editor exposes `cap` (Cap End), `rod` (Rod End). These are stable logical terminal IDs for diagram connectivity, not a promise that they equal physical package pin numbers.

Polarity and direction

This editor symbol does not encode a universal positive/negative orientation. Do not infer physical polarity or package pin numbering from left/right placement alone.

Reference designator

Project-defined: No single reference letter is asserted for this broad symbol. Apply the project standard and equipment-classification rules consistently.

Where the Hydraulic Cylinder symbol is used

• Hydraulic presses — forming, stamping, moulding — where the main ram is a large-bore cap-end-driven cylinder
• Excavator, loader, and crane boom/arm/bucket actuation on mobile equipment
• Dump-truck and trailer tipping using multi-stage telescopic cylinders
• Agricultural implements: three-point hitch lift, plough reversal, header height control
• Steel mills and foundries — gate, ladle, and roll-adjustment cylinders in high-temperature service
• Machine tools and fixtures: clamping, indexing, and tool-changer cylinders with pressure-reducing valves setting clamp force

Key facts

• The ISO 1219-1 double-acting cylinder symbol — rectangle, piston line, single rod, two ports — encodes powered motion in both directions; a spring inside the barrel would mark it single-acting.
• Force = pressure × effective area: full bore area on extend (Cap End pressurised), bore-minus-rod annulus on retract — so extension is stronger and slower, retraction faster and weaker.
• Differential flow: extending, the rod end discharges less than the cap end receives; retracting, the cap end discharges more than the pump supplies through the rod end — size valves and return lines for the larger flow.
• A 100 mm bore at 210 bar develops ≈165 kN (about 16.8 t) extending; with a 56 mm rod it retracts at ≈113 kN.
• Cushions (drawn as marks at the piston ends, with an arrow if adjustable) decelerate the final 20–50 mm of stroke to prevent end-cap hammering.
• Suspended or overrunning loads require counterbalance or pilot-operated check valves — a bare cylinder symbol holding a hanging load on a schematic is a red flag.
• Regeneration circuits reuse rod-end discharge into the cap end for fast (but reduced-force) advance — recognisable by the rod-end line teeing into the cap-end line.
• Telescopic cylinders (nested-rectangle symbol) trade force consistency for long stroke from a short collapsed length — standard on dump bodies.

Common interpretation mistakes

• Treating the Hydraulic Cylinder drawing (80 × 30 canvas units) as a physical footprint. The schematic outline expresses electrical intent; package and panel dimensions come from the selected physical profile.
• Copying `cap`, `rod` directly to a wire marker or manufacturer package pin number. These are logical Hydraulic Cylinder port IDs and require an exact ordered-part terminal map.
• Assuming every unlabelled or generic Hydraulic Cylinder terminal has the same role across manufacturers and variants.

Frequently asked questions

What is the difference between the cap end and rod end of a cylinder?

The cap end (also blind or piston end) is the closed end without the rod: pressure there acts on the full piston area and extends the cylinder with maximum force. The rod end is where the rod exits: pressure there acts on the smaller annulus (bore area minus rod area) and retracts the cylinder — faster but weaker. The symbol's two port stubs correspond directly to these connections.

How do I calculate hydraulic cylinder force?

Force = pressure × effective area. Extend: F = p × π/4 × bore². Retract: F = p × π/4 × (bore² − rod²). In convenient units, F(kN) = p(bar) × A(cm²) ÷ 100. Example: 80 mm bore (50.3 cm²) at 200 bar extends with about 100 kN; with a 45 mm rod (15.9 cm² rod area) it retracts with about 69 kN.

How is a single-acting cylinder drawn differently from a double-acting one?

A single-acting cylinder has one functional port; the return is by spring (drawn as a zigzag inside the barrel on the rod side) or by the load/gravity, and the non-powered end is vented or drained. A double-acting cylinder — this symbol — shows two ports and no spring: fluid powers both extend and retract. ISO 1219-1 defines both variants plus double-rod and telescopic forms.

Why does my cylinder extend slower than it retracts?

Because of the area difference the symbol encodes. A given pump flow fills the large cap-side volume slowly (slow, strong extend) but the smaller rod-side annulus quickly (fast, weaker retract). Speed = flow ÷ area. If retraction is instead the slow direction, look for meter-out flow controls, a counterbalance valve, or an undersized rod-end line on the schematic.

What stops a hydraulic cylinder from drifting down under load?

Not the directional valve alone — spool valves leak internally. Load-holding is done by pilot-operated check valves (lock the cylinder until pilot pressure releases them) or counterbalance valves (meter an overrunning load down and hold it against creep and hose burst). If a schematic shows a cylinder holding a suspended load with neither device, drift and a hose-failure hazard are built in. Cylinder seals also bypass slightly with age, adding to drift.

What does cushioning mean on a cylinder symbol?

Cushions decelerate the piston just before it reaches an end cap: a tapered spear enters a pocket and throttles the escaping fluid over the last 20–50 mm of stroke, preventing metal-to-metal hammering at full speed. ISO 1219-1 draws cushions as small rectangles on the piston line, with a diagonal arrow when adjustable. They matter on fast cylinders that regularly run to the mechanical end of stroke.

Sources and verification

• IEC 60617:2026 DB — Graphical symbols for diagrams (International Electrotechnical Commission) — The current official IEC graphical-symbol database and the electrotechnical areas it covers. Exact symbol identity data requires IEC access.; claim scope: standards
• IEEE/ANSI 315-1975 — Graphic Symbols for Electrical and Electronics Diagrams (IEEE Standards Association) — The official catalogue record for North American diagram symbols and reference-designation letters; IEEE lists the standard as inactive-reserved.; claim scope: standards, reference_designator
• IEC 61666:2010+AMD1:2021 — Identification of terminals within a system (International Electrotechnical Commission) — General principles for identifying terminals within systems; it does not replace the exact ordered-device datasheet.
• IEC 81346-2:2019 — Object classes and reference-designation codes (International Electrotechnical Commission) — The official classification scheme used to form reference designations across technical disciplines.; claim scope: reference_designator
• IEC 61082-1:2014 — Preparation of documents used in electrotechnology (International Electrotechnical Commission) — General presentation rules for electrotechnical diagrams, drawings, and tables.; claim scope: standards, usage

Geometry fingerprint: e5dfb59d1cdfaf23. A changed SVG, canvas size, or terminal definition invalidates the recorded review.

Related symbols

• Flow Control Valve symbol
• Limit Switch NO symbol
• Pneumatic Cylinder (Double Acting) symbol
• Pneumatic Cylinder (Single Acting) symbol
• Solenoid Valve symbol
• Pneumatic 5/2 Valve symbol

Physical breadboard, PCB, and panel mapping

No universal physical profile is published for this symbol yet. Create a versioned custom part from the exact manufacturer dimensions and terminal map before fabrication.

Place the Hydraulic Cylinder symbol directly on a wiring diagram or schematic in the free online editor — no download required.