In discussions of hydraulic energy consumption, attention usually goes to pumps, valves and motor efficiency; the piping is often overlooked. Yet in real systems, pressure loss along the lines accounts for a meaningful share of energy use — and a substantial part of that can be recovered through better line design.
1. Where the losses come from
Two mechanisms:
Friction (major) losses — friction between fluid and wall, proportional to length, inversely related to bore, and rising quickly with flow velocity (roughly with the square of velocity).
Local (minor) losses — eddy losses at bends, fittings, diameter changes and valve orifices where direction or section changes. In hose routing, tight bend radii, too many bends and repeatedly reversing routes all increase local losses sharply.
Both end up as heat, showing as rising oil temperature. Higher oil temperature accelerates rubber ageing and shortens fluid life — a self-reinforcing cycle.
2. Three effective optimisation points
1. Do not size to the absolute minimum. Designers often take the smallest workable bore for the required flow, but loss is inversely related to a high power of diameter — a modest increase in bore cuts loss substantially. Within space and cost limits, upsizing is often the most direct and economical efficiency measure. The trade-off is more fluid volume and higher hose cost.
2. Length and routing. Longer hose means more friction loss; reversing routes and redundant bends add local loss. Optimise in this order: shorten first, then reduce bends, then consider upsizing.
3. Bore finish and bend radius. A smoother bore gives lower friction; too tight a bend not only adds local loss but deforms the section, further increasing resistance. Routing to the specified minimum bend radius is both a reliability and an efficiency requirement.
3. Hose versus tube affects energy use
On long straight runs, tube generally has two advantages: smoother bore and straighter routing, so at equal bore its loss is usually lower than hose.
This points to an optimisation: tube for long straight runs, hose for flexible compensation — a combination that pays off in energy terms as well as in cost and life. Transitions between the two need smooth adapters to avoid extra local loss.
4. A knock-on benefit often missed
Reducing loss does more than save electricity:
Lower oil temperature → slower oil oxidation, longer drain intervals;
Slower rubber ageing → longer hose and seal life;
More stable system pressure → smoother actuator motion and less relief-valve loss.
In other words, line optimisation is one investment with several returns — which is why it deserves a high place on any efficiency retrofit list.
5. How to judge whether it is worth doing
A simple check: measure, under steady operating conditions, the pressure difference between pump outlet and actuator inlet, plus return-line temperature. If the differential is high or oil temperature runs persistently high, there is room to optimise.
Prioritise long runs, high-flow circuits and bend-dense routes — these usually show the clearest gains.