Excavator Unsmooth Movements or Lack of Power? The Issue Is the "Main Control Valve"!

I. Main Control Valve (Multi-Way Valve): The "Motion Control Center" of the Excavator—It Can’t Operate Without It!

   The main control valve, also known as the "multi-way valve", is simply a "hydraulic oil distribution center"—the high-pressure hydraulic oil generated by the main hydraulic pump must be distributed by the main control valve to various executive components such as the boom, bucket, swing mechanism, and travel system before the excavator can perform various movements. Without the main control valve, the excavator is like a "stiff piece of scrap metal", and its specific importance is reflected in the following 3 points:

1. Structure: Similar to a Pipeline Box with Multiple Switches, Easy for Beginners to Understand

The core composition of the main control valve is a "valve body + multiple spools", plus oil pipe interfaces connecting various components. There’s no need to memorize complex part names; just focus on mastering the following 2 key parts:

• Valve Body: Equivalent to a "main pipeline", it has multiple internal channels. After high-pressure hydraulic oil enters from the main pump, it is first stored in the main channel of the valve body, waiting for distribution;

• Spool: Equivalent to a "control switch", each movement (such as lifting the boom or retracting the bucket) corresponds to one spool. When you operate the control lever, the spool moves accordingly, opening the corresponding channel and delivering hydraulic oil to the respective cylinder or motor—for example, when you operate the "boom lift" control lever, the spool corresponding to the boom opens, and hydraulic oil flows into the boom cylinder to drive the boom up.

2. Core Principle: Distribute Hydraulic Oil on Demand to Ensure Smooth Movements

The entire process is similar to a "courier sorting center" and is completed in 3 steps:

1. The main hydraulic pump converts the engine power into high-pressure hydraulic oil and delivers it to the "main inlet" of the main control valve;

2. Operate the control lever (e.g., "retract the bucket"), the corresponding spool moves, opening the channel for the "bucket cylinder";

3. High-pressure hydraulic oil flows into the bucket cylinder through the opened channel, pushing the cylinder to extend or retract, and realizing the retraction of the bucket.

More importantly, the main control valve has the function of "simultaneously distributing hydraulic oil"—for example, when you operate the "boom lift" and "bucket retract" control levers at the same time, the two corresponding spools open synchronously, and hydraulic oil flows into the boom cylinder and bucket cylinder respectively. The machine can complete two movements at the same time, greatly improving work efficiency.

3. Importance: It Determines the Smoothness of Movements and Power Output!

• Determines Movement Smoothness: The more flexible the spool movement of the main control valve and the smoother the channels, the more evenly the hydraulic oil is distributed, and the smoother the excavator's movements—for example, no jerking when swinging the upper structure and lifting the boom at the same time; if the spool gets stuck, the movements will slow down, and the machine may even only perform single movements, reducing daily workload by up to 30%.

• Affects Power Output: The main control valve can adjust the pressure and flow of hydraulic oil. The higher the pressure and the more sufficient the flow, the stronger the movement power—for example, when digging hard rock, the main control valve will distribute higher-pressure hydraulic oil to the bucket cylinder to ensure the bucket can break through the hard rock; if the pressure adjustment function of the main control valve fails, the bucket will lose power and cannot dig normally.

• High Maintenance Costs: The unit price of an imported main control valve is usually 50,000-80,000 yuan (7,140-11,430), and domestic models also cost 15,000-30,000 yuan (2,140-4,290). During maintenance, the machine body needs to be disassembled and hydraulic oil replaced, resulting in a downtime of at least 2-3 days. The loss from work stoppage often exceeds the maintenance cost, making it a "core component with extremely high maintenance costs".

II. The Main Control Valve Needs to Guard Against These 5 Risks! Triggering Any of Them Requires High-Cost Repairs

Although the main control valve seems sturdy, it is actually sensitive to the following 5 types of operations or working conditions. Beginners must avoid them:

1. Hydraulic Oil Contamination: Easily Causes Spool Jamming

   When dust, metal debris (e.g., not replacing the filter in time) mixes into the hydraulic oil, it’s like "sand getting into a faucet"—it will get stuck in the gap between the spool and the valve body, causing the spool to fail to move normally. For example, if the spool corresponding to the bucket is stuck, the bucket cannot be retracted when operating the control lever, and the main control valve needs to be disassembled for cleaning. A single maintenance costs about 5,000-10,000 yuan (714-1,429).

2. Long-Term Violent Operation of the Control Lever: Accelerates Spool Wear

   Some operators push the control lever "all the way at once" in pursuit of efficiency, causing the spool to move suddenly and quickly, resulting in collision and friction with the valve body—similar to quickly turning a faucet on and off, the spool is prone to wear. Over time, the spool seal will age, leading to hydraulic oil leakage, which manifests as "insufficient movement power and slow speed". Replacing a set of spool seals costs 3,000-8,000 yuan (429-1,143).

3. Excessively High Hydraulic Oil Temperature: Easily Causes Valve Body Deformation

   When working in a high-temperature environment in summer or when the hydraulic oil radiator is blocked, the hydraulic oil temperature will exceed 60°C (the normal temperature should be ≤55°C). High temperature will cause the valve body of the main control valve to deform due to heat, narrowing the internal channels and hindering the flow of hydraulic oil. This leads to "jerky and slow movements"; in severe cases, the valve body may crack, requiring the entire main control valve to be replaced, which costs up to tens of thousands of yuan ($1,429+).

4. Insufficient Hydraulic Oil or Wrong Oil Type: Easily Causes Component Dry Friction

• Insufficient Hydraulic Oil: When the main hydraulic pump is short of oil, it will suck in air. After the air enters the main control valve, it forms "air resistance", causing the movements to be "uneven in speed" and accelerating spool wear at the same time;

• Wrong Oil Type: 46# anti-wear hydraulic oil should be used. If 32# hydraulic oil or ordinary engine oil is used by mistake, the oil viscosity will not meet the requirements, resulting in reduced lubrication effect. The wear rate of the spool and valve body will increase by 3 times, and the main control valve may be scrapped within 1-2 years.

5. Long-Term Overload Operation: The Valve Body Cannot Withstand High Pressure

   For example, using a 20-ton excavator to frequently dig hard rock, load heavy objects, or keeping the bucket in "full-load pressure" for a long time (e.g., forced pressurization when digging is blocked), the main control valve will be in a "high-pressure state" for a long time. The internal channels of the valve body will be deformed by pressure, and the spool will also wear due to excessive force. A main control valve with a original service life of 5 years may need to be replaced in 3 years.

III. Cost-Performance Comparison of Domestic and International Main Control Valve Brands

IV. Main Control Valve Maintenance: Do These 4 Things to Extend Service Life by 3 Years!

1. Regularly Replace Hydraulic Oil and Filters: Provide Clean Oil for the "Control Center"

• Hydraulic Oil: Replace it according to the instructions—every 2,000 hours for heavy-duty conditions (e.g., mining operations) and every 3,000 hours for light-duty conditions (e.g., municipal operations). Keep the oil level between "MIN" and "MAX" to avoid oil shortage;

• Filters: When replacing hydraulic oil, you must replace the "main hydraulic oil filter" and "return oil filter" at the same time. Check the filters every 500 hours during daily use, and replace them in time if they are dirty to prevent impurities from entering the main control valve.

2. Operate the Control Lever Smoothly: Avoid Violent Operation and Pressure Stalling

• Push and release the control lever slowly to ensure smooth movement of the spool and avoid sudden force;

• When digging hard soil or rock is blocked, avoid forced pressure stalling. Instead, move back and adjust the angle before trying again to prevent the main control valve from enduring high pressure for a long time.

3. Regularly Inspect 2 Key Parts: Detect Hidden Troubles Early

• Leakage Inspection: Check the oil pipe interfaces and spool seals of the main control valve every week to see if there is hydraulic oil leakage (leaked oil will form oil stains around the valve body). If leakage is found, replace the seals in time to avoid excessive oil loss;

• Temperature Inspection: When working in summer, touch the valve body of the main control valve with your hand (be careful to avoid scalding). If it feels "too hot" (temperature exceeding 60°C), stop the machine immediately to check the hydraulic oil radiator and clean the dust to prevent valve body deformation.

4. Maintenance During Long-Term Idleness: Prevent Component Aging

   If the excavator is idle for more than 1 month, start it every 10 days and operate all control levers (repeat each movement 3-5 times) to circulate the hydraulic oil in the main control valve, avoiding spool jamming and seal aging.

V. Conclusion

As the "motion control center" of the excavator, beginners need to remember 3 core points about the main control valve:

1. Avoid Damage Risks: Eliminate 5 taboos such as hydraulic oil contamination, violent operation of the control lever, and high-temperature operation to prevent the main control valve from being scrapped in advance;

2. Choose the Right Model: Prioritize international brands (such as Caterpillar and Komatsu) for heavy-duty operations, and domestic brands (such as Sany Heavy Industry and XCMG) for light-duty operations, balancing cost-performance and practicality;

3. Insist on Daily Maintenance: Regularly replace oil and filters, operate smoothly, and inspect for hidden troubles in a timely manner. Doing these 4 things well can extend the service life of the main control valve by 3 years and reduce maintenance costs.

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   - Founded in 2013, SPARKLING focuses on high-quality excavator parts across hydraulics, undercarriage, engines and electrical systems. We prioritize stability, precision and continuous service, offering worldwide distribution, tailored solutions and strict QC to help customers reduce cost and increase uptime.

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