Great Plains NH3 Safety User Manual
Page 20
16
NH
3
Safety
Great Plains Manufacturing, Inc.
407-551M
2013-07-15
Refer to Figure 12 (some components shown exploded for
clarity - never remove any except the outlet cap).
A66 Withdrawal Valve:
In field operations, this valve is
opened first, and
closed first.
The withdrawal valve is the application outlet valve.
It is usually located on the tank top, but may be
located on the bottom. It is color coded red or
orange.
The withdrawal valve may have an integrated bleed
valve or relief valve. Keep all bleed valves closed
except during disconnections. Be aware of relief
valves and stay up-wind of them.
A top-mount valve has a “dip tube”
which
collects the liquid NH
3
. Note that there is no pump.
Application flow is driven by:
a. vapor pressure of the NH
3
gas above, and
b. gravity siphoning due to tank elevation.
In cold weather, vapor pressure may be insufficient
to support high application rates. See page 25 for
further information on cold weather operations.
As there must be a gap between the dip tube inlet
opening and the tank bottom, there will be some
amount of ammonia that cannot be withdrawn as
liquid. This is normal and also provides safety. The
residual liquid ensures that the tank contains only
NH
3
, under positive pressure.
Ammonia Release Hazard:
Never open the withdrawal valve unless:
a. all other valves and bleed valves, are closed, or;
b. the implement is configured and ready for use.
Always be on the up-wind side for valve operation.
Always open slowly.
Always check for signs of release when opening this valve.
Explosion Hazard:
Stop application when the flow meter and cooler pressure
gauges indicate that the liquid level in the nurse tank has
reached the dip tube inlet. Leave the residual NH
3
in the
tank. Attempts to apply all of the liquid NH
3
could cause
air to be introduced to the tank, creating a potentially
combustible mixture.
Figure 12
Nurse Tank Withdrawal Valve
31574
A66a
NH
3
GAS
NH
3
LIQUID
A66
A66a