Lesson 4 of 5 · Pressure
Hydraulic hose pressure ratings explained
A hose has three pressures: the working pressure you design to, the proof pressure it is tested at, and the burst pressure it must survive once.
Three pressures
- Maximum working pressure is the highest pressure the hose may see in service, including surges. This is the number printed on the layline and the one used for selection.
- Proof pressure is a test pressure, normally twice the working pressure, applied briefly to check a hose or assembly without damaging it.
- Minimum burst pressure is the pressure a new hose must withstand before failing in a destructive test, normally four times the working pressure.
The ratio of four to one between burst and working pressure is the design factor. It is not spare capacity to use. It allows for pressure spikes, ageing, flexing and assembly variation over the life of the hose.
Working pressure by type and size
These are the maximum working pressures set by the standards, as commonly published. Many manufacturers offer hoses that exceed them, and the layline of the hose in your hand is the authority.
| Size | 1SN / R1 | 2SN / R2 | 4SP | 4SH | R12 | R13 | R15 |
|---|---|---|---|---|---|---|---|
| -04 / DN6 | 225 | 400 | 450 | — | — | — | — |
| -06 / DN10 | 180 | 330 | 445 | — | 280 | — | 420 |
| -08 / DN12 | 160 | 275 | 415 | — | 280 | — | 420 |
| -10 / DN16 | 130 | 250 | 350 | — | 280 | — | 420 |
| -12 / DN19 | 105 | 215 | 350 | 420 | 280 | 350 | 420 |
| -16 / DN25 | 88 | 165 | 280 | 380 | 280 | 350 | 420 |
| -20 / DN31 | 63 | 125 | 210 | 325 | 210 | 350 | 420 |
| -24 / DN38 | 50 | 90 | 185 | 290 | 175 | 350 | 420 |
| -32 / DN51 | 40 | 80 | 165 | 250 | 175 | 350 | — |
To convert: 1 bar = 14.5 psi, and 10 bar = 1 MPa. So 350 bar is 5,076 psi or 35 MPa.
Why pressure falls as the hose gets bigger
For the same wall construction, a larger bore puts more load on the reinforcement at the same pressure. A two-wire hose rated 400 bar in 1/4 in is rated only 165 bar in 1 in. Holding high pressure in a large bore needs more wire, which is why large high-pressure lines are four- or six-spiral.
Pressure spikes and impulse
System pressure is not steady. Every time a valve closes or a cylinder reaches the end of its stroke there is a spike above the relief setting. The hose working pressure must cover these spikes, not just the gauge reading.
Impulse life is the number of pressure cycles a hose survives. Circuits that pulse constantly, such as hammer and boom lines, wear out braided hose quickly and are specified with spiral hose.
The assembly is only as strong as its weakest part
The working pressure of a hose assembly is the lowest rating among the hose, the two fittings and any adapters. A 420 bar hose with a 350 bar fitting is a 350 bar assembly.
Frequently asked questions
What is the working pressure of a hydraulic hose?
The maximum pressure the hose is rated to carry continuously in service, including surges. It is printed on the hose and depends on the hose type and size.
What is the burst pressure of a hydraulic hose?
The pressure a new hose must survive in a destructive test. For most hydraulic hose it is four times the maximum working pressure.
What is the safety factor of hydraulic hose?
Four to one for most hydraulic hose: minimum burst pressure is four times maximum working pressure.
What is the working pressure of 1/2 inch 2SN hose?
The EN 853 2SN standard sets 275 bar (about 3,990 psi) for DN12, which is 1/2 in. Individual manufacturers may rate their hose higher; read the layline.
Can I use a hose above its working pressure if it is below burst pressure?
No. The margin between working and burst pressure is there for pressure spikes, ageing and flexing. Running above working pressure shortens hose life sharply and risks sudden failure.
Useful with this lesson
- Unit and dash-size converter
- Find hose length and fittings by machine model
- Hydraulic fitting types and how to identify them
- How to make a hydraulic hose assembly
Ratings and dimensions here are the nominal values set by the standards. The layline and data sheet of the actual hose take precedence.