In hydraulic system design reviews, the piping is often treated as the last thing to be drawn — merely the lines that connect components. Field experience says otherwise: once a system is running, most of the headaches — leaks, vibration, abrasion, noise — were planted during the layout stage.
Hose and tube are not a matter of "whichever is cheaper." They are two distinctly different engineering trade-offs.
1. Where each belongs
Hose (rubber or thermoplastic high-pressure hose) wins on flexibility: it absorbs vibration, tolerates misalignment and accommodates relative movement. The cost is a finite service life (rubber ages), greater sensitivity to temperature and fluid, and bulkier routing.
Tube (seamless steel, stainless, precision cold-drawn) wins on stability: better temperature capability, longer life, tidy routing, lower unit cost, and no rubber ageing. The cost is almost no flexibility — where vibration or relative displacement exists, stress goes straight into joints and welds.
The trade-off logic is straightforward:
Relative movement (booms, slewing, telescoping) → hose is mandatory.
Vibration isolation (pump outlet, valve block connections) → hose preferred.
Long straight runs, high temperature, demanding appearance and life → tube preferred.
High pressure with fixed routing → tube is more economical and reliable.
A common optimisation is "tube for the trunk, hose for the ends": long runs in tube for tidiness and life, with short hose sections only where flexibility is needed. This keeps hose usage — a consumable — under control while putting vibration isolation exactly where it belongs.
2. Six layout rules
1. Respect minimum bend radius. Bending tighter than specified concentrates stress locally and cuts impulse life sharply. Most hose covers carry a reference line; if it spirals after installation, the hose is twisted.
2. Avoid twist. The hose axis should be perpendicular to the plane of bending — never tighten a hose in while it is being twisted. Twisted installation adds torque at the coupling and is a leading cause of pull-off and leakage.
3. Leave slack — not excess. Too short and the hose is under tension; too long and it sags, swings and rubs against neighbours. Leave a small margin over minimum length; never stretch a hose to reach a fitting.
4. Keep clear of heat and moving parts. Near exhausts, turbochargers and oil coolers, radiant heat accelerates rubber ageing even when the hose's own temperature rating is adequate. Maintain clearance from moving parts and add protection where needed.
5. Clamp and support properly. Clamp spacing, material and mounting determine how a line behaves under vibration. Metal clamps with rubber liners are the common answer: secure, but allowing slight movement — and the clamp itself should not become a wear source.
6. Leave gaps between adjacent lines. Two lines rubbing against each other over time is the most overlooked wear mechanism. Keep clearance at layout stage; add sleeves or spacers at crossings.
3. Minimising leak points: from parts to assemblies
The traditional approach supplies hose, couplings and seals separately for on-site assembly — every joint made on the line is a potential leak point.
Increasingly, OEMs are moving to modular assemblies: several hoses, tubes, fittings and brackets pre-assembled in the factory into one module, with only a few interfaces to connect at final assembly. The benefit is direct: far fewer leak points, shorter assembly cycle time and clearer quality accountability.
The cost is a higher demand on the supplier: it must engage in the machine's routing design early, rather than simply build to a drawing.
4. Pre-delivery checklist
Bend radius within specification; no spiral in the hose reference line.
No tension, twist or interference with moving parts.
Clamp count and spacing adequate; liners intact.
Sufficient clearance from heat sources, sharp edges and wear points.
Gaps between adjacent lines; protection at crossings.
Pressure testing covers all newly installed lines, couplings included.