Hydraulic Repair Service

Servo Valve Repair vs. Proportional Valve Repair

Although the two terms are often used interchangeably, servo valves and proportional valves perform different functions within a hydraulic system.

Servo valves are designed for extremely precise positioning, speed control, and closed-loop motion applications where even minor variations affect machine accuracy. These valves are common in aerospace, injection molding, metal forming, and high-precision manufacturing equipment.

Proportional valves provide variable hydraulic flow and pressure control while offering a simpler and more economical solution for many industrial machines. They are widely used in packaging systems, material handling equipment, presses, food processing machinery, and automated production lines.

Both valve types require specialized testing equipment during repair. Internal leakage, contamination, worn feedback components, damaged spools, or calibration drift can all reduce system performance. Advanced Servo Technologies tests each repaired valve under operating conditions to verify flow, pressure, response, and overall performance before it is returned to service.

Common Signs Your Hydraulic Valve Needs Repair

Hydraulic valve problems and the need for industrial repair service rarely appear overnight. Many failures begin as subtle performance issues before becoming complete machine stoppages.

Common symptoms include:

• Inconsistent actuator movement
• Slow machine response
• Positioning inaccuracies
• Hydraulic pressure fluctuations
• Excessive heat generation
• Servo instability or oscillation
• Unexpected machine alarms
• Hydraulic fluid contamination
• External leakage
• Complete loss of motion

Repairing the valve before catastrophic failure often reduces downtime while preventing additional wear throughout the hydraulic system.

Our Hydraulic Valve Repair Process

Every hydraulic repair follows a structured process designed to identify both the immediate failure and any underlying conditions that could shorten the valve’s service life.

Incoming Inspection

Each valve is visually inspected and documented before disassembly. Technicians identify obvious wear, contamination, damaged connectors, corrosion, and mechanical failures.

Complete Disassembly and Cleaning

All internal components are carefully disassembled and cleaned using AST’s proprietary three-stage cleaning system. Removing microscopic contamination is critical because even small particles can affect spool movement and valve accuracy.

Component Inspection

Internal components are measured for wear, scoring, erosion, and dimensional accuracy. Components that no longer meet specification are replaced using high-quality replacement parts.

Reassembly and Calibration

Once rebuilt, every valve is calibrated to both OEM and customer specifications whenever applicable.

Dynamic Performance Testing

Unlike companies that only perform basic electrical testing, AST evaluates repaired valves on custom hydraulic test benches that simulate real operating conditions. Performance characteristics including pressure, flow, response time, hysteresis, and repeatability are verified before shipment.

Industries We Support

Our hydraulic repair services support facilities where reliable motion control is essential, including:

• Industrial manufacturing
• Food and beverage processing
• Packaging equipment
• Plastic injection molding
• Steel mills
• Automotive manufacturing
• Material handling
• Aerospace manufacturing
• Printing equipment
• Automation system integrators
• Robotics
• Machine builders

Whether maintaining a single production line or supporting multiple facilities, our team understands the urgency of minimizing downtime and restoring critical hydraulic systems quickly.

Hydraulic Valve Brands We Commonly Repair

AST repairs hydraulic servo valves and proportional valves from many of the industry’s leading manufacturers. Our technicians have experience diagnosing, rebuilding, calibrating, and testing valves used in demanding industrial applications, helping manufacturers extend equipment life while minimizing production downtime.

Bosch Rexroth

Bosch Rexroth hydraulic valves are widely used throughout manufacturing because of their precision, reliability, and broad range of motion control solutions. Their servo valves, proportional valves, and high-response valves are commonly found in industrial automation, injection molding, metal forming, machine tools, and other demanding hydraulic applications.

We repair a wide variety of Rexroth hydraulic valves, performing complete disassembly, inspection, proprietary cleaning, component replacement, calibration, and dynamic testing on custom hydraulic test equipment. Every repaired valve is evaluated to verify accurate pressure, flow, and response characteristics before being returned to service.

Moog Servo Valves

Moog has long been recognized as one of the industry’s leading manufacturers of high-performance servo valves. Their products are engineered for applications requiring exceptional accuracy, fast dynamic response, and precise control of position, pressure, flow, and force, making them common in aerospace, plastics, steel production, testing equipment, and other precision manufacturing environments.

Because Moog valves operate with extremely tight internal tolerances, contamination and normal wear can significantly affect performance over time. AST carefully rebuilds, calibrates, and tests Moog servo valves to help restore the responsiveness and precision required for critical hydraulic systems.

Parker

Parker hydraulic valves are trusted throughout manufacturing for dependable motion control and are commonly integrated into industrial machinery, mobile equipment, packaging systems, and automated production lines. Parker offers a broad range of proportional valves, servo valves, directional control valves, and flow control solutions that support a wide variety of hydraulic applications.

We provide repair services for many Parker hydraulic valve models, including complete cleaning, inspection, replacement of worn components, calibration, and functional testing.

Vickers

Vickers hydraulic valves have earned a long-standing reputation for durability and are found in manufacturing facilities around the world. Frequently used in presses, heavy industrial equipment, material handling systems, and automated machinery, Vickers proportional and servo valves continue to support many production environments, including legacy equipment that remains critical to daily operations.

Advanced Servo Technologies repairs many Vickers hydraulic valves by restoring worn internal components, removing contamination, recalibrating valve performance, and conducting comprehensive testing before shipment. Repairing existing Vickers valves can often provide a cost-effective alternative to replacing difficult-to-source components.

HR Textron

HR Textron hydraulic valves continue to be used in numerous industrial hydraulic systems where dependable motion control remains essential.

We repair HR Textron hydraulic valves using a thorough inspection and rebuilding process that includes complete disassembly, proprietary cleaning, replacement of worn components when required, calibration, and performance testing. Our experience with legacy hydraulic equipment helps manufacturers extend the service life of valuable production assets while minimizing unnecessary replacement costs.

Frequently Asked Questions

Can a servo valve be repaired instead of replaced?

In many cases, yes. Most failures are caused by contamination, worn internal components, damaged seals, or calibration issues that can be restored through professional repair and testing.

How long does servo valve repair take?

Repair times vary by valve model and parts availability, but Advanced Servo Technologies offers same-day rush repair for many common valves to minimize production downtime.

Do you test valves before returning them?

Yes. Every repaired valve is tested using AST’s custom hydraulic test equipment to verify proper operation and calibration before shipment.

What causes servo valves to fail?

The most common causes include hydraulic contamination, normal wear, overheating, improper filtration, damaged electrical components, corrosion, and extended service intervals.

Is repairing a hydraulic valve more economical than replacement?

For many industrial hydraulic systems, professional repair significantly reduces costs compared to purchasing a new valve while restoring OEM-level performance when completed and tested properly.