Product Overview

The YUKEN CPG Series is a range of pilot operated check valves designed for hydraulic load holding, actuator locking and controlled reverse flow.

Under normal flow conditions, the valve permits free flow in one direction. Reverse flow is blocked until hydraulic pilot pressure is applied to open the valve. This operating principle is documented in YUKEN’s hydraulic equipment catalog.

The models covered by the supplied product title include:

• CPG-03-30-20
• CPG-03-50-20
• CPG-06-E-30-20

The CPG series is a sub-plate-mounted configuration, while the E suffix identifies external drain. YUKEN documentation covers sizes 03, 06 and 10 with a maximum operating pressure of 25 MPa.

For industrial replacement projects, the valve can be supplied as an engineered replacement solution with in-place interchangeability based on the original mounting interface, complete type code and hydraulic operating conditions, together with 100% simulated working-condition testing prior to shipment.

Technical Specifications

CPG-03-30-20

• Manufacturer: YUKEN
• Series: CPG
• Valve Type: Pilot Operated Check Valve
• Mounting: Sub-plate Mounting
• Valve Size: 03
• Drain Type: Internal Drain
• Cracking Pressure Code: 30
• Cracking Pressure: 0.3 MPa, based on cross-referenced historical model information
• Design Number: 20
• Maximum Operating Pressure: 25 MPa
• Rated Flow: Approximately 40 L/min for size 03
• Control Method: Hydraulic Pilot Control
• Mounting Interface: ISO 5781 size-03 family
• Approx. Mass: Current CPG/CPDG-03 configuration is approximately 3.3 kg; the exact mass of the legacy 20-design version should be confirmed against the original revision documentation.

CPG-03-50-20

• Manufacturer: YUKEN
• Series: CPG
• Valve Type: Pilot Operated Check Valve
• Mounting: Sub-plate Mounting
• Valve Size: 03
• Drain Type: Internal Drain
• Cracking Pressure: 0.5 MPa
• Design Number: 20
• Maximum Operating Pressure: 25 MPa
• Rated Flow: Approximately 40 L/min
• Control Method: Hydraulic Pilot Control
• Mounting Interface: ISO 5781 size-03 family
• Approx. Mass: Approximately 3.3 kg for the current CPG/CPDG-03 configuration; verify the legacy 20-design mass against original documentation.

CPG-06-E-30-20

• Manufacturer: YUKEN
• Series: CPG
• Valve Type: Pilot Operated Check Valve
• Mounting: Sub-plate Mounting
• Valve Size: 06
• Drain Type: External Drain
• Cracking Pressure Code: 30
• Cracking Pressure: 0.3 MPa, based on historical model cross-reference
• Design Number: 20
• Maximum Operating Pressure: 25 MPa
• Rated Flow: Approximately 125 L/min for size 06
• Control Method: Hydraulic Pilot Control
• Mounting Interface: ISO 5781 size-06 family
• Approx. Mass: Approximately 5.4 kg for the current CPG/CPDG-06 configuration; exact legacy 20-design mass should be confirmed from the corresponding revision documentation.

YUKEN defines rated flow as an approximate flow value under specified test conditions rather than a universal maximum flow limit for every operating condition.

Key Technical Advantages

1. Hydraulic Pilot-Controlled Load Holding

The CPG valve uses hydraulic pilot pressure to control reverse flow.

This allows the valve to remain closed under reverse pressure until the pilot circuit commands opening. Such architecture is particularly useful for hydraulic cylinders, vertical loads and clamping systems requiring reliable actuator position holding.

2. 25 MPa High-Pressure Capability

YUKEN specifies a maximum operating pressure of 25 MPa / 3630 PSI for the CPG/CPDG family.

This pressure class is suitable for a broad range of industrial hydraulic power circuits, including:

• Hydraulic presses
• Cylinder systems
• Clamping equipment
• Lifting systems
• Material handling machinery

3. Standardized Sub-Plate Installation

The CPG series uses standardized sub-plate mounting interfaces.

YUKEN installation documentation identifies:

• Size 03: ISO 5781 size-03 family
• Size 06: ISO 5781 size-06 family
• Size 10: ISO 5781 size-10 family

This standardization is valuable for hydraulic manifold design, OEM equipment and retrofit applications.

4. Internal and External Drain Options

The CPG family is available with internal and external drain configurations.

For CPG-06-E-30-20, the E designation identifies the external-drain arrangement.

Drain configuration becomes particularly important when outlet-side back pressure exists, because drain routing directly affects the hydraulic behavior of the pilot-controlled valve.

5. Cracking Pressure Selection

Cracking pressure determines the minimum differential pressure required for free-flow opening.

Therefore:

CPG-03-30-20 and CPG-03-50-20 are not hydraulically identical.

Although both are size-03, design-20 configurations, their cracking-pressure settings differ. This can affect system pressure drop and flow behavior.

Historical product records confirm the existence of these distinct CPG configurations.

Application Areas

Typical applications include:

• Hydraulic Presses
• Injection Molding Machines
• Construction Machinery
• Lifting Platforms
• Material Handling Equipment
• Clamping Systems
• Machine Tools
• Steel Processing Machinery
• Industrial Hydraulic Power Units
• Hydraulic Cylinder Circuits
• Vertical Load-Holding Systems
• Industrial Automation Equipment

The valve is especially relevant where a hydraulic actuator must remain stable during standstill and then be released through a hydraulic pilot signal.

Expert Maintenance Tips

1. Verify the Complete Model Code

Before replacing a CPG valve, verify:

CPG + Valve Size + Drain Type + Cracking Pressure + Design Number

For example:

CPG-06-E-30-20

contains information that is lost if the valve is identified only as “CPG-06.”

2. Preserve the External Drain Arrangement

For CPG-06-E-30-20, the external drain connection must be correctly incorporated into the hydraulic circuit.

Check:

• Drain-line routing
• Drain back pressure
• Manifold drain port
• Pilot circuit
• Connection integrity

YUKEN documentation explicitly differentiates internal and external drain versions.

3. Control Hydraulic Contamination

Pilot-operated valves require clean hydraulic fluid for reliable operation.

During service:

• Clean the manifold mounting face.
• Prevent machining debris from entering pilot passages.
• Replace aged or damaged O-rings.
• Flush contaminated hydraulic lines.
• Verify filtration performance.

YUKEN documentation also provides sealing and O-ring information for the CPG/CPDG family.

4. Confirm 20-Design Compatibility Before Retrofit

The models supplied in your title belong to the older 20-design configuration, while many currently indexed YUKEN catalog entries focus on 50-design versions.

Historical records confirm models such as:

• CPG-03-30-20
• CPG-03-50-20
• CPG-06-E-30-20

Therefore, identical nominal size alone should not be treated as proof of complete hydraulic interchangeability.