Rexroth Hydraulic Valve Sizing Data Sheet | Nabor

Rexroth hydraulic valve sizing is not simply a comparison of maximum pressure and maximum flow. The useful sizing question is whether a valve can perform the required function over the machine’s normal operating range without creating an unsuitable pressure drop, control range or interface mismatch.

For purchasing teams, the best starting point is a short data sheet that separates confirmed operating data from estimates. That gives engineering and the supplier a common basis for reviewing the series and exact configuration.

Start with function, then nominal size

Directional, pressure, flow and proportional valves use different sizing logic. A directional valve needs the correct spool function; a pressure valve needs the correct pressure-control role; a flow valve needs the appropriate metering behavior; and a proportional valve adds command-signal and control-range requirements.

Nominal size only becomes meaningful after the hydraulic function is defined.

Use normal flow and maximum flow

Maximum flow protects against undersizing, but normal flow shows where the valve spends most of its working life. Oversizing can also reduce useful controllability in some applications, especially proportional or metering functions.

Where possible, record the estimated pressure differential across the valve at the required flow. Catalogue flow ratings are often specified at defined test conditions, so two published flow numbers should not automatically be compared as if they were measured under the same conditions.

The new model list shows why one sizing field is never enough

For the 4WRAE10 reference above, published product data identifies integrated electronics, 24 VDC supply and a ±10 V command interface for the A1 version. That illustrates why an electrical field can be just as important as hydraulic size for a proportional valve.

Mounting and electrical interfaces can limit the shortlist

• Subplate, sandwich, cartridge or threaded connection

• ISO mounting pattern and nominal size

• Port arrangement and pilot/drain connections

• Supply voltage and connector

• External amplifier or integrated electronics

• Command signal and position feedback where applicable

• Hydraulic fluid, seal material and temperature range

A valve that looks suitable from flow and pressure alone can still be unusable if the manifold or control system cannot accept it. The Rexroth directional control valve circuit guide gives more detail for spool and interface decisions.

Practical sizing data sheet for an RFQ

Common sizing mistakes

FAQ

Should maximum flow be the main sizing value?

No. Maximum flow is important, but normal flow, pressure differential and useful control range also matter.

Is system pressure the same as pressure drop across the valve?

No. System pressure describes the circuit pressure level; valve pressure drop is the difference across the active flow path while flow passes through it.

Can a complete part number replace sizing data?

It is a strong starting point for a like-for-like purchase. If the machine has changed or an alternative is being considered, current operating data should still be reviewed.

What if some values are not known?

Mark them as unknown or estimated and send the schematic, pump information and available measurements. That is safer than presenting assumptions as exact specifications.

Turn sizing data into a reviewable quotation

Once the basic operating envelope is documented, use the Bosch Rexroth Valve category to narrow product families. A supplier proposal should state which sizing inputs were confirmed and which assumptions remain.

Reference: Bosch Rexroth 4WRA proportional valve selector

Reference: ISO 4401 hydraulic valve mounting surfaces