49Rev. C, April 2017
BACKGROUND Moog D680 Series Proportional Control Valves
OPTIONAL VALVE FEATURES UPON REQUEST
49
BACKGROUND
Rev. C, April 2017
Moog D680 Series Proportional Control Valves
OPTIONAL VALVE FEATURES UPON REQUEST
Moog offers a variety of optional features for the D680
Series Proportional Control Valves including:
• Ruggedized valve for operation in demanding
environments
• High flow
• Fail-safe
• Special fluids
Decoupled electronics for high vibration environments
In highly dynamic applications such as presses, valves are
exposed to very high accelerations, vibration and shocks
exceeding the limits given in this catalog. If this happens
continuously, the valve electronics might be damaged
over time. To avoid this kind of damage, the valves can
be equipped with a damping plate between the valve
housing and the electronics. This damping plate partially
decouples the electronics from the valve housing, and thus
significantly lowers the stress on the electronics caused
by vibration. This option is suitable for vibrations with
frequencies above 300 Hz.
The mounting of a damping plate results in an extension
of the mounting length of the valve of 20 mm (0.79 in). The
extended valve dimension needs to be considered during
machine design.
Hardened valve housing to reduce wear
For applications where the valve operates at very high
pressure drops and can be subject to excessive wear of
control lands, Moog offers a version with hardened valve
housings. In these valves, the spool contact surfaces
including the control lands are plasma nitrided to increase
the surface hardness. This leads to reduced wear and
increased valve operation times.
High-flow version for 3/3-way applications (D684)
For use in 3/3-way applications with D684 (size 08)
valves, a valve version with higher rated flow is available.
This version uses a standard ISO 4401 port pattern with
a special port assignment. The flow directions are from
P → A + T with a higher rated flow (800 l/min @ 5 bar
pressure drop) and from B → P with standard rated flow.
Thus, by combining two ports for the flow leaving the
valve, the rated flow in one direction is increased. This
valve version is available with stub shaft spools only.
TPYX
5-Port Version for Use in Regenerative Circuits
For use in regenerative circuits, the valves sizes D681 to
D684 (size 05 to size 08) are available as 5-port versions
where the flow from the rod side of the differential
cylinder can be directly fed into the bore side. The sizes
D682 to D684 use a special port pattern that derives from
ISO 4401 and includes a 5
th
port A2.
Port A2 has to be connected to port A in the manifold. If
the differential cylinder is extended, the oil from the rod
side (connected to port B) is fed into port A2 and thus
port A, which is connected to the bore side of the cylinder.
This leads to a permanent regenerative circuit when
extending the cylinder.
TPYX
1
2
S
Hydraulically Actuated Fail-Safe Valve
Moog offers the option of a hydraulically actuated fail-
safe valve for applications where a solenoid actuated
fail-safe valve is not suitable. An additional feature
of this variant is that the main stage spool is moved
to the end position not only by mechanical springs,
but also by hydraulic force of the pilot oil. This leads
to more reliability in reaching the end position, as the
hydraulic force can easily overcome friction caused by
contamination or particles.
Valves for Operation with Phosphate Ester Based Fluids
Standard hydraulic seal materials, like NBR and FKM,
are often not compatible with fire resistant fluids based
on phosphate esters. For use of the valves with these
fluids, Moog offers valves with special seal versions that
are resistant to mineral oil as well as phosphate esters.
Please note: These valves are tested at Moog with mineral
oil. Remnants of mineral oil will remain in the valve after
testing.
Please contact Moog for more details on special versions
available for your application.
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