SUN Hydraulic CBIG LJN Cartridge Valve

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Product details

CBIG-LJN (Sun Hydraulics)

Brand: Sun Hydraulics, USA

Type: 3-port internal drain high-flow counterbalance cartridge valve with 4.5:1 pilot ratio. Designed for heavy load holding and preventing load runaway or free fall. Matches large-size T-19A cavity.

1. Model Code Explanation (CBIG-LJN)

- CBI: Counterbalance valve series, T-19A large cavity, internal drain

- G: 4.5:1 pilot ratio

- L: High flow rating

- JN: Standard pressure rating, right-hand adjustment

2. Main Technical Parameters (T-19A Cavity)

- Cavity: T-19A (High-flow specification)

- Rated flow: 480 L/min (127 gpm)

- Maximum working pressure: 350 bar (5000 psi)

- Pressure adjustment range: 70–280 bar (1000–4000 psi)

- Preset pressure (fully clockwise): Approx. 14 bar (200 psi)

- 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 multiplied by 4.5 will be superimposed on the set pressure

- Installation torque: 475–508 Nm (350–375 lbf·ft)

- Weight: Approx. 1.36 kg

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

- Port 1: Load port (Connect to large-bore cylinder or high-speed motor)

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

- Port 3: Pilot control port (Internal drain, no independent external drain port)

4. Operating Principle

1. Forward flow (Port 2 → Port 1): The check valve fully opens for low-resistance flow up to 480 L/min.

2. Reverse flow (Port 1 → Port 2): The main valve remains closed to lock heavy loads and avoid free fall or load runaway.

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

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

5. Key Features (vs. CBDG-LKN / CBEA-LIN)

- High-flow design with T-19A cavity and rated flow of 480 L/min (CBDG-LKN & CBEA-LIN: 30 L/min)

- 4.5:1 pilot ratio plus internal drain structure delivers high pilot sensitivity with obvious back pressure influence. Ideal for high-pressure, high-flow and heavy-load working conditions.

- 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 outstanding stability under heavy loads.

6. Typical Applications

- Construction machinery: Boom and arm cylinders of large excavators, luffing and hoist cylinders of heavy-duty cranes, aerial work platforms

- Industrial hydraulics: Large lifting tables, heavy telescopic booms, high-pressure high-flow clamping and synchronous circuits

- Operating conditions: Medium to high pressure, large flow rate, severe vibration and heavy load holding requirements

7. Installation & Commissioning Guidelines

- Set pressure: Adjust 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 pressure margin must be reserved.

8. Interchangeable Models (Same T-19A Cavity)

- CBIG-LJN: 4.5:1 pilot ratio, internal drain, 480 L/min (Standard model)

- CBIA-LJN: 3:1 pilot ratio, internal drain, 480 L/min

- CBIG-LKN: 4.5:1 pilot ratio, external drain, 480 L/min

I. Product Overview

TheCBIG-LJNis a standard counterbalance valve manufactured by SUN Hydraulics, designed primarily for controlling overrunning loads. It allows unrestricted one-way flow of hydraulic fluid from the directional valve (Port 2) to the load port (Port 1) while regulating flow from Port 1 to Port 2 through a direct-acting, pilot-assisted relief valve function. Additionally, pilot assistance at Port 3 reduces the effective setting of the relief function by the pilot ratio factor. This valve is also referred to as a motion control valve or over-center valve.

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II. Technical Features

1. Pilot-Assisted Control:

Adjusts the effective setting of the relief function via pilot pressure, enhancing control flexibility and precision.

2. Floating Structure Design:

SUN's floating design minimizes interference caused by excessive installation torque or bore machining errors, improving reliability and service life.

3. Sealing Performance:

The valve provides complete sealing between all ports, ensuring a leak-free system.

4. Modular Design:

All 3-port counterbalance valves, load control valves, and pilot-operated check valves are structurally interchangeable, facilitating system design and maintenance.

5. Corrosion-Resistant Options:

Corrosion-resistant models are available for harsh environments, identified by the suffix "/AP."

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III. Functions and Applications

1. Overrunning Load Control:

Prevents load overspeed descent, ensuring system safety.

2. Unidirectional Free Flow:

Allows unrestricted fluid flow from the directional valve to the load port, reducing energy loss.

3. Relief Control:

Precisely regulates fluid flow from the load port to the directional valve via pilot-assisted relief functionality, maintaining stable system pressure.

4. Cavitation Prevention:

Optional low check valve cracking pressure (e.g., 4 psi/0.3 bar) prevents actuator cavitation.

5. Application Fields:

Widely used in construction machinery, industrial hydraulic systems, marine industries, and other sectors requiring precise load control.

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IV. Technical Specifications

• Pilot Ratio: 4.5:1

• Maximum Setting Pressure: 350 bar (5000 psi)

• Maximum Recommended Load Pressure: 270 bar (3850 psi)

• Flow Capacity: Up to 720 L/min

• Reseat Pressure: 85% of valve opening value under standard settings

• Leakage: Maximum of 0.3 cc/min during reseating