CBDG LKN Cartridge Valve

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Product details

CBDG-LKN (Sun Hydraulics)

Brand: Sun Hydraulics, USA

Type: 3-port internal drain standard counterbalance cartridge valve with 4.5:1 pilot ratio. Designed for load holding and preventing load runaway or free fall.

1. Model Code Explanation (CBDG-LKN)

- CBD: Counterbalance valve series, T-2A cavity, internal drain (non-external drain)

- G: 4.5:1 pilot ratio

- L: Standard flow rate (7.5 gpm)

- KN: Standard pressure rating, right-hand adjustment

2. Main Technical Parameters (T-2A Cavity)

- Cavity: T-2A (Medium size, larger than T-11A and smaller than T-17A)

- Flow rate: 30 L/min (7.5 gpm)

- Maximum working pressure: 350 bar (5000 psi)

- Pressure adjustment range: 70–280 bar (1000–4000 psi); Approximately 14 bar (200 psi) when fully turned clockwise

- Pilot ratio: 4.5:1 (Pressure reduction via Port 3)

- Check valve cracking pressure: 1.7 bar (25 psi)

- Drain type: Internal drain (No separate external drain port). Back pressure at Port 2 will be superimposed on the set pressure

- Installation torque: 61–68 Nm (45–50 lbf·ft)

- Weight: Approx. 0.23 kg

3. Port Definition (3-port, Internal Drain)

- Port 1: Load port (Connect to cylinder or motor)

- Port 2: Directional valve port (Connect to directional control valve)

- Port 3: Pilot control port (No separate external drain port)

4. Operating Principle

1. Forward flow (Port 2 → Port 1): The check valve opens to allow free flow with low resistance.

2. Reverse flow (Port 1 → Port 2): The main valve stays closed to balance the load and avoid free fall or load runaway.

3. Pilot control (Port 3): Applied pilot pressure reduces the cracking pressure of the main valve at a 4.5:1 ratio for smooth load lowering.

4. Internal drain design: The spring chamber drains to Port 2. The back pressure at Port 2 will be multiplied by 4.5 and added to the set pressure.

5. Key Features (vs. CACA-LIN / CBGA-LHN)

- Medium-size design with T-2A cavity and 30 L/min flow rate (CACA-LIN: 60 L/min; CBGA-LHN: 240 L/min)

- Internal drain & 4.5:1 pilot ratio: Noticeable back pressure influence and high pilot sensitivity. Suitable for high-pressure, low-flow applications requiring fast response.

- Zero internal leakage: Excellent sealing performance from Port 1 to Port 2 for reliable load holding.

- Reset accuracy: No less than 85% of the set pressure, ensuring superior operational stability.

6. Typical Applications

- Construction machinery: Boom and arm cylinders of medium & small excavators, forklift lift cylinders, crane luffing cylinders

- Industrial hydraulics: Lifting platforms, telescopic booms, servo synchronous systems and high-pressure clamping circuits

- Operating conditions: Medium to high pressure, medium & low flow, heavy vibration, and applications demanding fast pilot response

7. Installation & Commissioning Guidelines

- Set pressure: Set to no less than 1.3 times the maximum load pressure to prevent pressure drift.

- Adjustment: Turn clockwise to decrease pressure; turn counterclockwise to increase pressure.

- Back pressure effect: The back pressure at Port 2 multiplied by 4.5 will be superimposed on the set pressure. Sufficient margin shall be reserved during commissioning.

8. Interchangeable Models (Same T-2A Cavity)

- CBDG-LKN: 4.5:1 pilot ratio, internal drain, 30 L/min (Standard)

- CBEA-LHN: 3:1 pilot ratio, internal drain, 30 L/min

- CBEG-LJN: 10:1 pilot ratio, internal drain, 30 L/min

I. Structural Composition

The CBDG-LKN cartridge valve typically consists of a valve spool, valve sleeve, spring, and seals. Its compact and modular design allows for easy insertion into hydraulic manifolds or valve blocks, forming a complete hydraulic system. This structure facilitates convenient installation, maintenance, and upgrades.

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II. Functional Characteristics

1. Overrunning Load Control: The CBDG-LKN cartridge valve effectively controls overrunning loads, ensuring stable operation of the hydraulic system.

2. Unidirectional Free Flow: It allows unrestricted one-way flow of hydraulic fluid from the directional valve (Port 2) to the load port (Port 1), minimizing energy loss.

3. Relief Control: Through a direct-acting, pilot-assisted relief valve function, it precisely controls fluid flow from Port 1 to Port 2, maintaining stable system pressure.

4. Pilot-Assisted Opening: The pilot assistance at Port 3 reduces the effective setting of the relief function by the pilot ratio factor, enhancing control flexibility and accuracy.

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III. Technical Specifications

1. Pilot Ratio: The CBDG-LKN cartridge valve typically has a pilot ratio of 4.5:1, meaning that changes in pilot pressure have a minimal impact on the relief valve setting, improving system stability.

2. Flow Capacity: Flow capacity varies depending on the specific model and configuration. For example, some models offer a flow capacity of up to 60 L/min (15 gpm), meeting diverse application requirements.

3. Pressure Setting: The valve's setting should be at least 1.3 times the load pressure value to ensure system safety and stability. Additionally, turning the adjustment clockwise reduces the setting value, lowering the pressure.

4. Sealing Performance: The CBDG-LKN cartridge valve is fully sealed between all ports, preventing hydraulic fluid leakage and ensuring normal system operation.

5. Floating Structure: The floating structure minimizes interference caused by excessive installation torque and machining errors in bore profiles, enhancing valve reliability and service life.

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IV. Application Scenarios

The CBDG-LKN cartridge valve is widely used in fields requiring precise hydraulic control, such as:

1. Construction Machinery: In excavators, loaders, cranes, and other construction machinery, it controls load movement and stability, improving operational efficiency and safety.

2. Industrial Automation: In automated production lines, robots, and other industrial automation applications, it precisely controls the actions of hydraulic actuators, enabling automated production.

3. Other Fields: It is also applicable in aerospace, marine, energy, and other sectors requiring precise hydraulic control.