8
B. Type ‘3’ spool is designed with ports (A) and (T)
interconnected and ports (P) and (B) blocked in the
center position.
A B
P T
Pressure and ‘‘B’’ Closed - ‘‘A’’ Open to Tank
T
A
P
B
C. Type ‘6’ spool is interconnected at ports (A), (B) and
(T). Port (P) is blocked in the center position.
Pressure Closed - ‘‘A’’ & ‘‘B’’ Open to Tank
A B
P T
T
A
P
B
D. Type ‘31’ spool is a type ‘3’ spool reversed in the
bore. A type ‘31’ spool is interconnected at ports (B) and
(T), but blocked at ports (P) and (A) in the center position.
A B
P T
Pressure and ‘‘A’’ Closed - ‘‘B’’ Open to Tank
T
A
P
B
E. Type ‘33’ spool provides controlled leakage from port
(A) and (B) to port (T). Port (P) is blocked in the center
position.
A B
P T
Closed Center - Bleed ‘‘A’’ & ‘‘B’’
T
A
P
B
F. Type ‘52’ spool
A B
P T
Closed Center, Regen. by Solenoid ‘A’
T
A
P
B
G. Type ‘521’ spool
A B
P T
Closed Center, Regen. by Solenoid ‘B’
T
A
P
B
H. Type ‘56’ spool
T
A
P
B
A B
P T
I.
Type ‘561’ spool
T
A
P
B
A B
P T
3. Tandem spools (4 and 8 types): Tandem spool valves are
used in hydraulic circuits where two or more hydraulic
cylinders or motors are controlled from a single source of
power. The valve’s spool is designed so that in center
position, all cylinder connections are blocked and full pump
delivery is connected to tank. The tank connection of one
valve may be connected to the pressure connection of
another valve and both valves operated simultaneously as
long a the combined pressures developed by the two loads
are within the capabilities of the power source.
