Hydraulic Installation Calculator

Designing a Hydraulic Installation

Every hydraulic system, from a simple bench press to an industrial work handler, follows the same sizing path: decide how fast the cylinder must move, work out the flow that requires, select a pump that can deliver it, and then choose pipe and hose lines with the right internal diameter so pressure losses stay acceptable. This calculator walks through all four steps from just three inputs — cylinder bore, rod diameter, and target extension speed.

The piston area drives everything. Area is calculated from the bore diameter, and on retraction the area is reduced by the rod, which is why a cylinder returns faster than it extends at constant flow. Flow (Q) is simply area times speed, converted into L/min; pump capacity in cc/rev is then derived by dividing the required flow by the typical motor speed. With the flow known, the tool recommends suction, pressure, and return line diameters using accepted fluid velocities of 1, 5, and 3 m/s.

Line Sizing Tables

Recommended tube selections are highlighted in the DIN 2391 precision tube table and the hydraulic hose table. Standard pressure ratings follow the ISO 3320 bore/rod series, and the ISO cylinder and rod diameter lists help you snap a custom value to the nearest standard size. Rows shown with a red border are discouraged combinations; the gold row marks the correct internal diameter for the return line.

Worked Example

A Ø100/56 cylinder extending at 12 cm/s needs an area of 78.5 cm², giving a flow of about 47 L/min. The calculator recommends a suction line near 31 mm, a pressure line of roughly 14 mm, and a return line of about 18 mm, then highlights the matching DIN 2391 tube and hose entries for that return flow — exactly the information needed for the hydraulic circuit drawing and the bill of materials.

Speed Limits and CE

Piston speed is entered in cm/s and the results also print it in mm/s, because that is the unit used on cylinder data sheets. Two practical ceilings apply: standard cylinders with NBR/PU seals are generally rated to 0.5 m/s (50 cm/s), and 1.0 m/s (100 cm/s) is only allowed with low-friction (PTFE) or Viton rod seals. The calculator flags the result as soon as the extension or the return speed crosses these values — the return speed is usually the higher one, because the rod reduces the piston area.

Regarding CE, the Machinery Directive 2006/42/EC does not define a numeric piston speed limit. The binding number is the rated speed on the cylinder data sheet, and for the installation the relevant safety standard is EN 982 (fluid power — safety requirements for systems and their components). Hydraulic cylinders themselves are pressure equipment and fall under the Pressure Equipment Directive 2014/68/EU, not under 2006/42/EC. Running a cylinder above its rated speed therefore breaks the declared conformity of the machine, which is a risk-assessment item under the Machinery Directive rather than a fixed number in the standard.