CAUTION
DISASSEMBLY, MAINTENANCE, OR REPAIR OTHER THAN IN ACCORDANCE WITH THE
INSTRUCTIONS HEREIN OR OTHER SPECIFIC WRITTEN DIRECTIONS FROM MOOG WILL
INVALIDATE MOOG’S OBLIGATIONS UNDER ITS WARRANTY.
D661 Series
ISO 4401 Size 05
Installation and Operation Instruction
Servo and Proportional Control Valves with Integrated Electronics
1. INTRODUCTION
This manual provides instructions and procedures necessary
to install, operate and troubleshoot the Moog D661 Series Servo and Propor-
tional Control Valves.
2. OPERATION
General
The Servovalves D661-G, S and H Series and the Proportional Flow
Control Valves D661-P Series are throttle valves for 2-, 3- and 4-way
applications. With proportional flow control valves, 5-way applications are also
possible. These valves are suitable for electrohydraulic position, velocitiy,
pressure or force control systems with high dynamic response requirements.
D661-G, S and H
The spool of the main stage is driven by a nozzle flapper or ServoJet
®
pilot stage, optional with or without additional mechanical feedback (nozzle
flapper only).
With versions D661-
S
and
H
in case of an electrical supply failure
the spool is moved into a preferred position by action of an additional
mechanical feedback.
ELECTROHYDRAULIC VALVE CUT-AWAY
Figure 1 Moog Series D661-G Series, without additional mechanical feedback
X T
A
P
B
T
2
Y
Connector
Spool
Bushing
Screw Plug for Null Adjust
Series Models
Series G
Servovalve with nozzle-flapper or ServoJet
®
pilot
stage, spool in bushing, without additional mechanical
feedback
Series S
Servovalve configured like version G, but with additional
mechanical feedback
Series H
Servovalve configured like version S, but with improved
performance (high response)
Series P...A/B
Proportional valve with ServoJet
®
pilot stage, spool in body,
without additional mechanical feedback
Series P...F/G
Proportional valve configured like version P...A/B, but
with nozzle flapper pilot stage and additional mechanical
feedback
