Adjusting the counter balance valve – Great Plains 2S-2600HDF Operator Manual v1 User Manual
Page 23
Great Plains Manufacturing, Inc.
Preparation and Setup
19
2014-05-16
195-440M
Refer to Figure 11 on page 18 and Figure 12 at right
4.
Release locking discs
on down-pressure valves.
Adjust knobs
on pressure-control valves for
opener down pressure so gauges
are at:
1800 psi for 2S-2600/F models
2100 psi for 2S-2600HD/HDF models.
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 1800 psi (2100 psi for heavy duty models). 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 51.
Note: The higher the bypass pressure, the greater the
potential for oil heating and premature tractor
damage. At the same time, for proper opener
operation the bypass valve must be set at least 300
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 300 psi above the opener
down pressure setting.
While 1800 psi (2100 psi for heavy duty models) 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 below1800 psi
(2100 psi for heavy duty models). If you consistently
operate the drill with very high opener down pressure,
you may need a bypass-valve setting above 1800 psi
(2100 psi for heavy duty models). See also
“Opener-Subframe Adjustment” on page 52.
Adjusting the Counter Balance Valve
Refer to Appendix: “Counter Balance Valve” on page 102
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 12
Down Pressure for Bypass
26471
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