Detailed Application of Hydraulic Valve Blocks in Excavators

1. Main Valve Block (the "Main Controller" for Overall Machine Actions)

• Integrated Valve Groups: It internally integrates main directional control valves, main relief valves, overload replenishing valves, flow control valves, etc. Among them, the main directional control valve is mainly used to control the direction of actions; the main relief valve plays a role in protecting the maximum pressure of the system; the overload replenishing valve can prevent negative pressure in the actuator; and the flow control valve can adjust the action speed.
• Core Functions:
  1. Boom Action Control: It switches the oil flow direction with the help of the main directional control valve to realize the lifting, lowering, or stopping of the boom. At the same time, it adjusts the lifting and lowering speed of the boom through flow control—for example, reducing the speed to ensure stable pressure under heavy load conditions.
  2. Arm and Bucket Action Control: It coordinates the retraction and extension of the arm, as well as the digging and unloading actions of the bucket. During digging operations, for instance, a pressure compensation valve is used to ensure stable bucket power and avoid action jamming caused by load changes.
  3. Slewing Action Control: It adjusts the forward rotation, reverse rotation, and rotation speed of the slewing platform, and uses a slewing buffer valve to reduce the hydraulic impact generated when the slewing platform starts and stops. For example, it prevents the machine body from shaking when the slewing platform stops suddenly.
  4. Travel Action Control: It independently controls the forward and backward movement of the left and right crawlers, and realizes high-low speed switching through a travel speed valve—for example, using high-speed travel during transition and low-speed travel during operation to ensure stability.
  5. System Protection: The main relief valve sets the maximum pressure of the system (usually 30-35MPa) to prevent the hydraulic pump and pipelines from bursting due to overload; the overload replenishing valve replenishes oil in a timely manner when the actuator acts rapidly, avoiding cavitation.

2. Pilot Valve Block (the "Control Signal Source" for the Main Valve)

• Integrated Valve Groups: It mainly integrates pilot directional control valves, pilot relief valves, check valves, etc. The pilot directional control valve is used to output control signals; the pilot relief valve protects the pressure of the pilot oil circuit; and the check valve prevents oil backflow.
• Core Functions:
  1. Receiving Operation Instructions: It converts the mechanical displacement of the driver's operation handle into hydraulic signals. For example, when the driver pushes the handle, the pilot valve outputs low-pressure oil in the corresponding direction.
  2. Precise Control of the Main Valve: The low-pressure pilot oil pushes the spool of the main directional control valve to move, thereby controlling the on-off of the main oil circuit. The larger the stroke of the handle, the higher the pressure of the pilot oil, the greater the displacement of the main spool, and the faster the action speed—realizing "stepless speed regulation".
  3. Pilot Oil Circuit Protection: The pilot relief valve limits the maximum pressure of the pilot oil circuit to avoid damage to the pilot valve or main valve caused by excessive operation force.

3. Auxiliary Valve Block (the "Supplement" for Specialized Functions)

• Slewing Buffer Valve Block: It internally integrates a buffer valve and a check valve, and its main function is to reduce the hydraulic impact generated when the slewing platform starts and stops. For example, when the slewing platform stops suddenly, the buffer valve releases pressure slowly to prevent the machine body from "swinging".
• Travel Speed Limiting Valve Block: It integrates a speed limiting valve and a solenoid valve. During operation, it can limit the travel speed to prevent the machine from moving rapidly due to misoperation; during transition, it can release the speed limit to improve movement efficiency.
• Boom Holding Valve Block: It includes a pressure maintaining valve and a check valve. After the boom is lifted, it can keep the boom in the current position, preventing the boom from falling slowly due to oil leakage and ensuring the safety of hoisting operations.
• Breaker/Grapple Valve Block: It integrates a directional control valve and a pressure regulating valve. When the excavator is connected with auxiliary tools such as a breaker or a grapple, this valve block can control the actions of the auxiliary tools—for example, adjusting the striking frequency of the breaker and controlling the opening and closing of the grapple.

II. Common Materials of Hydraulic Valve Blocks and Selection Basis

1. 45# High-Quality Carbon Structural Steel (the Most Mainstream)

• Material Properties: It has a tensile strength of ≥600MPa, a yield strength of ≥355MPa, moderate hardness (HB197-241 without heat treatment), is easy to perform cutting processes such as drilling, slotting, and honing, and has relatively low cost.
• Processing Technology:
  1. The entire valve block undergoes quenching and tempering treatment (quenching + high-temperature tempering) to make the overall hardness of the valve block reach HB220-250, improving its compressive strength and deformation resistance.
  2. The internal oil circuit holes are processed by honing to ensure the hole wall roughness is Ra≤0.8μm, reducing the resistance of oil flow and the wear of the valve stem.
• Application Scenarios: It is widely used in core valve blocks such as main valve blocks and pilot valve blocks. More than 90% of excavators currently use this material—for example, the main valve blocks of Komatsu PC200 and Sany SY215 are made of 45# steel.

2. 27SiMn Alloy Structural Steel (for High-Pressure/Heavy-Load Scenarios)

• Material Properties: As a low-alloy high-strength steel, it has a tensile strength of ≥835MPa, a yield strength of ≥685MPa, better impact toughness than 45# steel (impact energy ≥34J at -40℃), and superior fatigue resistance.
• Processing Technology: First, it undergoes quenching and tempering treatment to make the hardness reach HB240-280; then, local surface quenching is performed on the valve block, especially on the inner wall of the oil circuit holes. After quenching, the hardness can reach HRC50-55, improving its wear resistance.
• Application Scenarios: It is mainly used in the main valve blocks of large excavators (e.g., over 20 tons) and dedicated valve blocks for breakers. These valve blocks need to withstand higher pressure and impact—for example, the main valve block of Caterpillar 336 is made of 27SiMn alloy structural steel.

3. Aluminum Alloy (for Lightweight Scenarios)

• Material Properties: The commonly used aluminum alloy grade is 6061-T6, with a density of only 1/3 that of steel (2.7g/cm³), achieving a significant lightweight effect. Its corrosion resistance is also better than that of steel, and it can effectively resist oil corrosion after surface oxidation treatment. However, its tensile strength is relatively low (≥310MPa), and its pressure resistance is poor.
• Processing Technology: The surface of the aluminum alloy valve block undergoes anodizing treatment to form an oxide film with a thickness of 5-10μm, further enhancing its corrosion resistance; the internal oil circuits are processed by precision CNC (Computer Numerical Control) technology, such as CNC drilling and reaming, to ensure the precision of the oil circuits.
• Application Scenarios: It is suitable for pilot valve blocks or auxiliary valve blocks of small excavators (e.g., under 6 tons, such as Kubota U-50). These excavators are sensitive to weight and operate at relatively low pressure (usually ≤20MPa).

4. Stainless Steel (for Corrosion-Resistant Scenarios)

• Material Properties: The commonly used stainless steel grades are 304 or 316, which have extremely strong corrosion resistance and can resist the erosion of acids, alkalis, and oil. However, they have low hardness (HB≤187), high processing difficulty (prone to tool adhesion), and high cost—3-5 times that of 45# steel.
• Processing Technology: The stainless steel valve block undergoes solution treatment to improve its corrosion resistance; the internal oil circuits are processed by EDM (Electrical Discharge Machining) to ensure the precision of the oil circuits meets the requirements.
• Application Scenarios: It is mainly used in auxiliary valve blocks (such as travel speed limiting valve blocks) of excavators working under special working conditions, such as mines and coastal areas. In these environments, excavators are easily exposed to corrosive substances such as dust and seawater.

III. Summary

1. High skilled and well-trained working team under good management environment;
2. Quick response and support for any inquiries;
3. Over 10 years professional manufacture experience to ensure high quality of your products;
4. Large and strong production capacity to meet your demand;
5. High Quality standard and hygienic environment;
6. We have very strict quality control process:
   a. In coming Quality control (IQC) – All incoming raw material are checked before used.
   b. In process quality control (IPQC) – Perform inspections during the manufacturing process.
   c. Final quality control (FQC) – All finished goods are inspected according to our quality standard for each products.
   d. Outgoing Quality Control (OQC) – Our QC team will 100% full inspection before it goes out for shipment.
7. Good after sales services;