CETOP (Comité Européen des Transmissions Oléohydrauliques et Pneumatiques) defines standard valve mounting interfaces. Now standardized as ISO 4401. CETOP sizes: 03=NG6, 05=NG10, 07=NG16, 08=NG25, 10=NG32.

How to calculate flow through a hydraulic valve?

Q = Kv × √(ΔP/SG) where Q is flow in L/min, Kv is flow coefficient, ΔP is pressure drop in bar, and SG is specific gravity (0.86-0.90 for hydraulic oil). Kv values are published by valve manufacturers.

How is power loss calculated?

Power loss P_loss = Q × ΔP / 600 (kW), where Q is flow in L/min and ΔP is pressure drop in bar. This heat must be dissipated by the hydraulic oil cooler.

How to select the right CETOP valve size?

Size based on required flow rate: CETOP 03 (NG6) for 40-80 L/min, CETOP 05 (NG10) for 80-120, CETOP 07 (NG16) for 120-350, CETOP 08 (NG25) for 350-600, CETOP 10 (NG32) for 600-1000 L/min. Oversizing wastes space; undersizing causes excessive pressure drop and heat.

What pressure rating do CETOP valves have?

Most CETOP directional valves are rated 315 bar (4600 psi). Some high-performance CETOP 03/05 go to 350 bar. Always verify the specific valve's pressure rating.

Free Engineering Tool

Hydraulic Valve CETOP Sizing & Flow Calculator

Size CETOP/ISO 4401 valves based on flow rate and pressure drop. Calculate flow capacity (Kv), power loss, and recommended valve size.

ISO 4401CETOP 03–10Flow Kv

Results

Recommended CETOP Size

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Required Kv

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Power Loss through Valve

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Heat Generation

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Mounting Dimensions

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Port Sizes

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Bolt Pattern

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Velocity in Ports

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Flow Capacity (Kv)

Power Loss

CETOP Size Reference

CETOP	NG	P,T Ports	A,B Ports	Bolts	Face (mm)	Typical Kv	Flow (L/min)
03	NG6	G3/8	G3/8	4×M5	69.9×36.5	8–12	40–80
05	NG10	G1/2	G1/2	4×M6	102.4×56.4	15–25	80–120
07	NG16	G3/4	G3/4	4×M8	152×80	30–50	120–350
08	NG25	G1	G1	4×M10	197×102	55–80	350–600
10	NG32	G1-1/4	G1-1/4	4×M12	255×130	90–120	600–1000

Practical Example

Example — Select valve for 80 L/min, ΔP=8 bar

Required Kv = 80 / √(8/0.87) = 80 / 3.03 = 26.4

CETOP 05 has typical Kv = 15–25 → borderline → CETOP 07 (NG16) recommended

Power loss = 80 × 8 / 600 = 1.07 kW

Hydraulic Valve CETOP Sizing & Flow Calculator | ISO 4401 | Free Tool

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

Flow Capacity (Kv)

Power Loss

CETOP Size Reference

Practical Example