Technical guides
How to specify a hydraulic hose and get it right
A hose is ordered by what runs inside it, by the pressure it holds and by the fitting that connects it. If any of the three is missing, what arrives is no use.
Mobile equipment on a mine or a jobsite is not stopped by the hose: it is stopped by the wrong hose. And the mistake is almost never the diameter, which is the one thing usually stated when ordering.
The five data points that define it
1. Inside diameter
Flow rate sets it, not whatever fitting was there before. A diameter too small for the flow raises fluid velocity, generates heat and degrades both the oil and the hose from the inside.
2. Working pressure
Two figures need separating here. Working pressure is the circuit under normal operation. Peak pressure is what happens when a valve slams shut, and it can be several times the nominal value.
The hose is specified for the peak, not the average. It is the most frequent cause of premature bursts in circuits that “were working fine”.
3. End fitting and its standard
JIC, camlock, barb with clamp, threaded: each fitting follows a different standard and a different sealing method. Two fittings that screw together does not mean they seal.
The fitting is crimped to the hose with a machine and a die matched to that specific hose-and-fitting combination. It is not a part to improvise in the field.
4. Fluid
Mineral hydraulic oil is the ordinary case, but not the only one. Synthetic fluids, esters, water-glycol and fuels call for different inner-tube compatibility. An incompatible tube swells or dissolves, and it does not always fail suddenly: sometimes it contaminates the circuit first.
5. Temperature
Both fluid and ambient. A hose running next to an exhaust or under open-pit sun ages far sooner than its data sheet suggests.
The error that shortens life most: bend radius
Every hose has a minimum bend radius. Installed tighter than that, the reinforcement braid works badly, the inner tube is pinched and the hose fails in a fraction of its expected life.
The practical assembly rule: the bend does not start at the fitting. Leave a straight section coming out of the crimp before the hose begins to curve, because that point is the stiffest part of the assembly.
Length: measure the route, not the old hose
The old hose stretched in service. Copying its length leaves the new one long, so it rubs against the structure — the second cause of failure after bend radius.
The right approach is measuring the actual route between the two connection points, allowing for equipment movement if the hose follows a cylinder or a boom.
Suction and discharge are not the same
A suction hose works under negative pressure: without spiral reinforcement it collapses. A discharge hose works under positive pressure and can be layflat, which flattens when empty and takes up little space.
Putting a discharge hose on suction guarantees the line closes on itself as soon as the pump starts.
What to send when requesting a quote
- Inside diameter and the length of the route.
- Working pressure and, if known, the peak.
- Fitting type at each end and its angle.
- Fluid and temperature.
- A photo of the hose in place: it settles in one second what takes three emails in writing.
Frequently asked questions
Not advisable. The crimp is calculated for a specific hose-and-fitting combination, with its die and crimp diameter. Mixing components changes retention and creates a failure point under pressure.
Almost always a bend radius below the minimum, or rubbing against the structure. Check that there is a straight section coming out of the fitting and that the hose is not longer than it needs to be.
No. Suction works under negative pressure and needs spiral reinforcement; a discharge hose collapses. You have to specifically order suction hose.
