The servo valve plays a critical role in the performance of a hydraulic positioning, velocity or pressure control application. Moog Mechanical Feedback Servo Valves incorporate a feedback mechanism that precisely determines the position of the spool in the valve and stops it at a position that is proportional to the electrical input of the valve. This technological breakthrough revolutionized the industry and has made Moog synonymous with servo valves more than 60 years later.

There are three keys to increasing longevity, minimizing unplanned downtime and ensuring reliable performance in servo valves. These include:

• The selection of carbide material as ball on the feedback mechanism
• The incorporation of ball-in-hole spool design
• The integration of brazing to bond the carbide ball to wire

Carbide ball construction
After one billion test cycles, stainless steel ball exhibits visible wear. Carbide and sapphire do not. Moog uses the carbide ball due to its proven performance and long life. The carbide material also has the advantage of enabling the feedback mechanism wire to be bonded with a brazing process, providing even greater reliability in industrial environments.

Ball-in-hole design 
Today, more than 95% of all Moog Mechanical Feedback Servo Valves have been converted to ball-in-hole technology due to its superior performance and extended lifetime in industrial applications.

Brazing in the manufacturing process
Brazing is a specialized soldering process that joins the carbide ball andstainless steel wire at temperatures above 232 °C (450 °F). This manufacturing process is only possible with carbide—not sapphire—and is critical inenabling the ball to withstand both high temperatures and deterioration from chemicals in the hydraulic fluids. 

For more information on Moog’s superior performance and extended lifetime in industrial applications, download our FREE White Paper on “Three Keys to Specifying Long Life Servo Valves”.