Hydraulic hoses: what to tell the seller

A burst hydraulic hose stops the machine and sprays hot oil. Most shops can press (crimp) a new hose while you wait, if you bring the right information. Better still, bring the old hose.

1. Inside diameter

Hoses are sized by the inside diameter, often as a “dash” number: -04 is 1/4 inch, -06 is 3/8, -08 is 1/2, -12 is 3/4. Do not go smaller than the old hose: the oil gets hot and the machine gets slow.

2. Pressure

The hose’s working pressure must be at least the highest pressure in your system.

• 1SN (R1): one steel braid, for medium pressure.
• 2SN (R2): two steel braids, higher pressure. The most common on machines.
• 4SP / 4SH: steel spiral, for very high pressure and heavy shocks.

3. The fittings at each end

This is where most mistakes happen. Common types are BSP, JIC (37° cone), ORFS (flat face with an O-ring) and metric DIN 24°. Some look alike but do not seal together. The seller can identify them from the old hose, or measure the thread and the angle of the seat.

4. Length and angle

Measure from the end of one fitting to the end of the other. If both ends are angled, mark how they turn against each other.

Safety

Never feel for a leak with your hand. A pinhole jet of oil can go through skin, and that needs a hospital at once. Use a piece of cardboard.