Great Plains 2S-2600HDF Operator Manual v2 - Manual (Page 24)

20 2S-2600HD Table of Contents Index Great Plains Manufacturing, Inc.
195-069M Table of Contents Index 2014-02-03
Refer to Figure 12 on page 19 and Figure 13 at right
4.
Release locking discs on down-pressure valves.
Adjust knobs on pressure-control valves for
opener down pressure so gauges are at 1500 psi.
5. While watching gauges on drill, slowly turn knob on
bypass valve counterclockwise. Adjust bypass valve
just until needles on gauges begin to move down
from 1500 psi. Lock bypass valve at this setting.
(See also note below.)
6. Re-adjust pressure-control valves on drill to desired
opener down pressure as explained under See
“Opener Frame Down-Force” on page 62.
Note: The higher the bypass pressure, the greater the po-
tential for oil heating and premature tractor dam-
age. At the same time, for proper opener operation
the bypass valve must be set at least 100 psi above
the opener down-pressure setting when the tractor
is at one-half throttle. Therefore, you should set the
bypass valve as low as possible while staying at
least 100 psi above the opener down pressure set-
ting.
While 1500 psi is a good starting point for setting the
bypass valve, if you consistently operate the drill with low
opener down pressure you can set the bypass valve
below 2100 psi. If you consistently operate the drill with
very high opener down pressure, you may need a
bypass-valve setting above 2100 psi. See also
“Opener-Subframe Adjustment” on page 64.
Adjusting the Counter Balance Valve
On the stem of the valve there is a rubber cap that pro-
tects the threads of an adjustment stem. This stem is
locked in place with a hex nut. To adjust the valve, loosen
the nut and turn the stem using an Allen wrench.
Screwing the stem in (clockwise) pushes on a spring
which supplements the pilot line’s force on an internal
piston. More spring force will let the valve open with a
low pilot pressure. Less spring force will require higher
pilot pressure to open the valve.
Note: With the screw turned in fully, the spring will
develop enough force on the piston to unlock the
valve, even with no pilot pressure, causing the
openers to settle.
Raise and lower the drill several times then hold hydrau-
lic down pressure on the openers to purge air from the
system and to warm the oil. Repeat.
Raise the openers. Observe the openers closely to detect
settling. If the openers remain up, no valve adjustment is
needed.
If the openers settle, the stem is screwed in too far. Gently
back the stem out until it stops, then screw it in one turn.
Generally this is a good starting point. Check for settling.
Backing the stem out will lock the valve, screwing it in too
far can cause it to unlock.
A small increase in lowering speed can be achieved by
screwing the stem in.
Figure 13
Down Pressure for Bypass
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