3/8 Inch Hydraulic Hose | Sizes, Models & Specifications

3/8 Inch Hydraulic Hose runs on a 9.5–10.1 mm bore with a 18.1 mm outside diameter in 1SN and 19.5 mm in 2SN. Minimum bend radius is 130 mm and the assembly weighs 0.34 kg/m dry. YIBO supplies this bore in 1SN, 2SN and 4SP constructions to EN 853 and EN 856.

The numbers that decide the specification are rarely the ones printed on the datasheet. What matters is the relief valve setting, the peak pressure during a dead-head, the flow rate at working temperature, and how much space the routing actually leaves you. This page works through all four for the 3/8 inch bore, including the cases where a larger hose makes the problem worse rather than better.

3/8 Inch Hydraulic Hose: Pressure Rating by Construction

Working pressure below is the continuous rating at 30–60 °C with a 4:1 burst margin, measured against EN 853 / EN 856 and SAE J517. Burst pressure is not a service condition — it is the point at which the assembly fails in a test rig.

1SNBraided, 1 wire18.0 MPa (180 bar)View full specification →2SNBraided, 2 wire22.5 MPa (225 bar)View full specification →4SPSpiral, 4 wire44.5 MPa (445 bar)View full specification →

Two things change the usable rating in practice. Temperature: above 80 °C the elastomer softens and the working pressure should be derated. Impulse: a line that cycles between zero and full pressure more than 100,000 times needs the next construction up, not a longer service interval.

Note also that the fitting, not the hose, usually sets the pressure ceiling of a finished assembly. A 4SP hose crimped with a 2SN-rated ferrule is a 2SN assembly. If the circuit runs near the hose rating, confirm the fitting rating separately before assuming the assembly is good for it.

Dash Size and Bore Reference

Dash numbers are sixteenths of an inch, so 06 means 6/16 inch nominal. The highlighted row is this bore. The flow ceiling assumes 4–6 m/s in a pressure line; return lines tolerate less, suction lines far less again. It is a routing guide, not a rating.

Where 3/8 Inch Hydraulic Hose Is Used

• Forklift main circuits. Lift, tilt and side-shift lines on counterbalance trucks. 3/8 inch covers most 2–3 tonne classes; the routing around the mast is what limits the bend radius.
• Agricultural loader hydraulics. Tractor and telehandler implement circuits. Oil is often hot and contaminated, so cover abrasion and inner tube compatibility matter as much as pressure.
• Excavator pilot and secondary. Secondary circuits and attachment lines where flow sits between 10 and 18 L/min. The most common field replacement size in small earthmoving.
• Injection moulding machines. Clamp and ejector circuits on small to mid tonnage presses. Cycle counts are high, so impulse rating drives the construction choice.
• Tail lifts and dock levellers. Vehicle-mounted equipment where the hose is exposed to weather and road spray. UV and ozone resistance of the cover is the deciding factor.
• Utility vehicle power packs. Compact hydraulic power units for sweepers, lift platforms and access equipment.

Choosing Between 3/8 Inch and Its Neighbours

Stepping down to 1/4 inch. If the circuit only needs 8 L/min and the 3/8 inch assembly is fighting for space, 1/4 inch (6.2–7.0 mm bore) is the right move — but check that the pressure rating still clears the relief setting.

Stepping up to 1/2 inch. Above roughly 18 L/min the velocity in a 3/8 inch bore pushes pressure drop and oil temperature up faster than most circuits tolerate. Moving to 1/2 inch (12.3–13.5 mm bore) cuts velocity by more than half for the same flow.

There is a second-order effect worth knowing about. Moving up a size reduces velocity but increases the volume of oil that has to be accelerated every time a valve shifts, which shows up as a slower response and a softer feel at the actuator. On a machine where the operator notices response time, a slightly higher pressure drop in the smaller bore can be the better trade. Size for the flow, then check the feel.

Fittings for 3/8 Inch Hydraulic Hose

This bore takes BSPP 3/8", JIC 9/16-18, ORFS 11/16-16 and metric M18×1.5 fittings. It is the most commonly mixed size in repair work — check whether the original assembly used a DIN 24° cone or a 37° flare before ordering.

Crimp diameter, not torque, determines whether the joint holds. YIBO supplies assemblies crimped to the fitting manufacturer's chart and pressure-tested per batch; if you crimp in-house, recalibrate the machine after every ferrule supplier change.

Installation and Routing

• Bend radius. 130 mm is the static minimum. On any line that flexes or pulses, plan for 20 % more. A hose held at the minimum radius fails at the fitting transition, not in the middle.
• No twist. Route the hose so the lay line stays straight along its length. A quarter turn of twist costs roughly half the service life, and twist is invisible once the assembly is clamped in place.
• Support. At 0.34 kg/m dry — more when filled — horizontal runs need clamps. Space them closer than you would for a rigid pipe, and never let the hose weight hang on the fitting.
• Clearance. Allow 20–25 mm around the outside diameter so the hose does not chafe against structure or another line.
• Temperature. Keep at least 100 mm from exhaust and manifold surfaces, or fit a heat sleeve. Radiant heat degrades the cover long before the hose bursts.
• Bend plane. Keep the first bend out of the fitting in the same plane as the second. Out-of-plane bends put a torsional load into the crimp that no pressure rating covers.

Pressure Drop and Flow

Pressure drop in a 3/8 inch bore rises with roughly the square of flow, so doubling the flow quadruples the loss. At the 18 L/min ceiling quoted above, a typical mineral oil at 46 cSt loses noticeably more pressure per metre than at half that flow — which is why a circuit that works cold can starve the actuator once the oil reaches operating temperature.

The practical checks are simple. If the actuator is slow at the far end of a long run, measure pressure at both ends rather than guessing at the pump. If oil temperature climbs steadily under steady load, the restriction is in the line, not the cooler. If the return filter goes into bypass when the machine is warm, the return line is undersized for the flow.

Common Misapplications

• Matching bore but not pressure. Ordering by the size printed on the old hose and ignoring the construction. Two hoses with the same outside diameter can differ by a factor of three in working pressure.
• Matching pressure but not temperature. A hose rated for the pressure at 40 °C is not rated for the same pressure at 100 °C. Continuous duty above 80 °C needs a derated figure or a different compound.
• Ignoring the peak. Relief valve settings describe the steady state. Dead-heading a cylinder against a stop produces a spike well above the relief setting for a few milliseconds, and that spike is what fatigues the wire.
• Reusing fittings. A crimped ferrule is a one-time component. Cutting the hose back and re-crimping the same ferrule leaves the wire layer disturbed and the grip unreliable.

Why Hose Fails at This Size

• Mismatched cone angle — a 24° cone fitting forced onto a 37° flare seat leaks at the first pressure cycle.
• Abrasion on the outer cover where the hose crosses a frame edge; add a sleeve rather than a larger bend radius.
• Using 4SP where 2SN would do, which triples the weight and stiffens the line unnecessarily.

In field returns, the split is fairly consistent: roughly half the failures trace to installation — bend radius, twist, or missing support — rather than to the hose itself. Checking the routing before blaming the supplier is usually the faster route to a fix.

Standards This Bore Is Supplied To

The figures on this page are the regular supply values for this bore. Where a customer specification differs, the batch test certificate governs — ask for it before releasing an order.

Test certificates are issued per batch, not per metre. If your customer's incoming inspection asks for burst test data, say so on the order — retesting a finished assembly is destructive, so the record has to come from the production run.

Maintenance and Replacement

• Inspection interval. Check at every service interval, and immediately after any event that put the line under abnormal load — a cylinder hitting a stop, a hose pulled taut, or a fitting exposed to impact.
• What to look for. Cover cracks that expose the wire, blisters or soft spots under the cover, weeping at the crimp, and any change in the lay line that suggests the hose has rotated in its clamps.
• When to replace. Any exposed wire, any blister, any leak. A hose that has been re-routed, re-clamped or re-crimped should be treated as new and re-inspected after the first shift.
• Storage. Coiled, out of sunlight, away from ozone sources such as electric motors. A hose stored in a hot, sunny yard ages faster than one in service.

Ordering and Custom Assemblies

• Bulk hose. Supplied in coils; the standard coil length is confirmed at order because it varies by construction and bore.
• Cut lengths. Cut to order with a tolerance confirmed before production. State whether the length is measured end-to-end or between fitting flats.
• Assemblies. Send the fitting type at each end, the angle of any bent tube, and the working length. Assemblies are crimped to the fitting manufacturer's chart and pressure tested before packing.
• Marking. Neutral packing or your own label, as required for the destination market.
• Documentation. Material certificate, dimensional report and pressure test record can be supplied with the shipment.

For a replacement of an imported assembly, the fastest route is a photo of the original fitting alongside its thread measurement. Cone angle, thread pitch and seat depth are what actually decide compatibility — the nominal size on the drawing rarely tells the whole story.

Inside the YIBO Factory

Certifications and Approvals

Hydraulic hose is a pressure component, so approvals are not decoration. The ABS factory approval is a class society audit of the production system and test capability; the mining safety mark is the entry requirement for coal equipment; the environmental and quality certificates cover the supplier audits that export customers increasingly run.

Frequently Asked Questions

What is the outside diameter of a 3/8 inch hydraulic hose?

18.1 mm for 1SN and 19.5 mm for 2SN. Allow 20–25 mm of clearance around the hose when planning a route through a tight frame.

What is the working pressure of 3/8 inch 1SN hose?

18.0 MPa (180 bar), with a burst pressure of 72.0 MPa (720 bar). That is the EN 853 / SAE 100R1AT minimum for this bore.

Can I use 3/8 inch hose for a return line?

Up to roughly 18 L/min. Above that the velocity and pressure drop climb quickly and oil temperature follows. Step up a size rather than accepting the loss.

What fittings fit a 3/8 inch hose?

This bore takes BSPP 3/8", JIC 9/16-18, ORFS 11/16-16 and metric M18×1.

Is 4SP available in this bore?

Yes — 4SP is rated 44.5 MPa (445 bar) here, more than double the 2SN rating.

What is the minimum bend radius?

130 mm static. Treat it as a floor, not a target.

How long should this hose last?

It depends almost entirely on impulse cycles and routing quality rather than on calendar age. A well-routed line on a steady-duty circuit can run for years; the same hose held at the minimum bend radius on a high-cycle machine may need replacing within a season.

Can I mix constructions in one circuit?

You can, but keep the pressure rating consistent. A 4SP hose feeding a 2SN-rated manifold does not make the manifold a 4SP component — the weakest element sets the ceiling for the whole circuit.

Tell us the working pressure, flow rate, fluid and fitting type, and YIBO will confirm the exact model, bend radius and crimp specification within one working day.