Four measurements before ordering a hydraulic hose

Inside diameter

Measured on the bore, not the outside of the hose — the outside diameter includes the cover and changes with the pressure rating. Sizes are commonly given as dash numbers, where each dash is 1/16 inch: -4 is 1/4 inch bore, -6 is 3/8, -8 is 1/2, -12 is 3/4.

Fitting type and thread

The fitting ends must be identified by standard, not by eye:

• BSP (parallel or tapered) — common in Europe and much of Asia; sealed by a bonded washer or on the thread.
• JIC 37° flare — sealed by the cone, common on US equipment.
• NPT — tapered pipe thread, sealed on the thread.
• Metric DIN and ORFS — sealed by an O-ring face; often confused with JIC in photographs.

Length and orientation

State the length as the distance between the sealing faces of the two fittings, and say whether the elbows are at 0° or 90° to each other. Two hoses with identical lengths and different elbow orientation are not interchangeable.

Working pressure, not burst pressure

Order against the working pressure of the system, with the safety factor applied by the hose standard, not against the burst figure printed on the hose. Also check the minimum bend radius for the installed routing — a hose bent tighter than its radius fails at the fitting, not in the middle.