OCB Service Information Type OA 3 Operating Mechanism.pdf

This document is an Installation, Operating, and Maintenance Instructions manual for the Type OA-3 hydraulic operating mechanism, a hydraulically-closed mechanical device that operates oil circuit breakers at high speeds using compressed nitrogen gas in an accumulator system.

The Type OA-3 mechanism is designed to open and hydraulically reclose breakers in 20 cycles, with energy for five closures stored by compressing nitrogen gas in an accumulator and additional opening energy stored in breaker springs during closure. The mechanism operates through a system of valves, pistons, and mechanical linkage, with manual or electrical operation capabilities. Key technical specifications include: accumulator precharge pressure of 1625±25 psi at 60°F; nitrogen gas purity requirements of 99.9% minimum with maximum oxygen of 0.1%, maximum hydrogen of 0.0%, and maximum moisture of 0.0012%; acceptable hydraulic fluids including Shell Aeroshell Fluid No. 4, Standard Oil RPM Aviation, Texaco Aircraft AA, and Humble Oil Esso Univis J-43; and motor-driven pump operation controlled by pressure switches for system pressurization. The document provides detailed installation requirements including electrical connections, miscellaneous parts handling, hydraulic fluid specifications and filling procedures, precharge pressure verification and adjustment, and final preparation steps. Section VI addresses operation and safety blocking with procedures for normal-speed operation, slow-speed positioning using maintenance-positioning valve 19, blocking in open and closed positions for service, and safety precautions for personnel. Section VII covers reference data and adjustments including accumulator precharge specifications, pressure switches settings, over-pressure relief valve adjustments, and pilot valve rod specifications. Section VIII details routine maintenance including fluid leak checks, general cleanup, lubrication of linkage parts with specified oils, pressure storage system checks, fluid level monitoring, pump operations, mechanism adjustments, pressure switch verification, and auxiliary switch inspection. The spare parts list includes opening and closing coils for 48, 125, and 250 volt DC applications, X and Y relay coils, pressure switch assemblies, and pressure line valve block components, with quantities specified per installation requirement.