10
7.
Tandem Operation
- Tandem operation permits
operation of two banks of valves from the same pumping
source. An internal plug in the outlet section of the first
bank (see Figure 8) separates the by-pass passage from
the tank passage. Cylinder exhaust oil is returned to tank
via the alternate discharge port, and by-pass oil is
directed out the primary discharge port to the by-pass
port of the bank.
In Figure 8, either bank can be operated separately
or both simultaneously. This is possible because of the
tandem by-pass connection from the inlet connection of the
first bank to the F inlet connection of the second bank. If
neither bank is operating, part of the fluid flows through both
by-pass passages directly to tank. The balance is diverted
through the tank passage of the first section as shown in
Figure 2.
In some cases, it is desirable to have tandem valves
connected in series where, the second bank is dependent
upon the operation of the first bank. The first bank has
control priority because the tandem by-pass connection is
not used. The cylinder by-pass oil of the first bank is directed
out of primary discharge port to the inlet port of the second
bank. Use a
“
K
”
inlet section in the first bank if full flow is
desired to the second bank. Otherwise reduced flow will be
encountered.
C. Non-Operating Sections
1.
General
- The CM2 valve non-operating sections are
the
“
E
”
and
“
L
”
outlet sections and a center
“
U
”
section.
These sections do not have operating spools. The functions
of these sections are as follows:
a.
“
E
”
Outlet Section
- The
“
E
”
type section provides
an outlet section by which the by-pass feature for pump
unloading is extended to a subsequent valve bank (tandem
operation). It is generally used in conjunction with the
“
F
”
type
inlet section on the subsequent valve bank assembly. This
“
E
”
type section is only used with one spool banks.
b.
“
L
“
Outlet Section
- The
“
L
”
type section is
basically the same section as the
“
E
”
section except it
provides only one connection for exhaust oil and is used as
the last section on a single spool bank where tandem
operation is not required.
c.
“
U
“
Center Section
- The
“
U
”
section, when
mounted between two operational sections, permits the
operation of two cylinders or motors in series. This is
accomplished by porting the outlet of the first operating
section to the inlet of the second operating section.
NOTE
It should be noted that the pressure drop across the
valve, when used in series operation, will be the
sum of the pressure drops for each section.
Figure 7.
Tandem
Outlet
Section
“
E
”
Inlet
First Bank
Discharge
To Tank
+ = Separates By-Pass and Tank Passages in
“
E
”
Section.
Plug +
Second Bank
Discharge
To Tank
Tandem Inlet
Section
“
F
”
A
A
A
B
B
B
A
B
