Moog D633-A Series, User Manual

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3 Product Description Safety function/fail-safe
© Moog GmbH User Manual "D633-A Series" (CA80942-001; Version 1.0, 12/08) 14
3.2.1.1 Valves with fail-safe function F, D or M
Fail-safe functions
F, D and M
In the case of the fail-safe functions F, D and M, the mechanical setting of the
linear force motor or corresponding centering springs at the factory establishes
which position the spool assumes in the mechanical fail-safe state.
Position of spool:
Ö
Table 1, page 14
3.2.1.2 Mechanical fail-safe state
The valve is in the mechanical fail-safe state when the spool is in a defined
spring-determined position.
Position of the spool in
the mechanical fail-safe
state
3.2.1.3 Fail-safe identification
Fail-safe identification
(6th position in type
designation)
The fail-safe identification, i.e., the 6th position in the valve type designation,
indicates which mechanical fail-safe function is integrated in the valve.
Overview of type designation:
Ö Chapter "3.5 Nameplate", page 18
Fail-safe
function Position of spool
F Defined position of spool: approx. 10 % valve opening: P t B and A t T
D Defined position of spool: approx. 10 % valve opening: P t A and B t T
M Defined overlapped center position of spool
The mechanical fail-safe function M gives rise only in conjunction with spools which
have an overlap greater than ±10 %, i.e., in valves with bushing-spool identifica-
tion D, to the defined overlapped center position.
In the case of a smaller overlap, i.e., in valves with a different bushing-spool identifi-
cation, a defined overlapped center position is not possible.
Ö Chapter "3.2.1.4 Bushing-spool identification", page 15
Table 1: Position of the spool in the mechanical valve fail-safe state
Type designation:
1 2 3 4 5 6 7 8 9 10
A
• •
K
•
5
• • • • •
Ident. Fail-safe function Further information
F Valves with fail-safe function F Ö Table 1, page 14
Ö Chapter "3.2.1.1 Valves with fail-safe
function F, D or M", page 14
D Valves with fail-safe function D
M Valves with fail-safe function M
X Valves with special fail-safe function
Table 2: Fail-safe identification in the type designation
fail-safe identification