System discharge, Normal discharge – Great Plains NP30A 30-foot Operator Manual User Manual
Page 114
110
NP30A or NP40A
Great Plains Manufacturing, Inc.
407-502M
2014-05-20
System Discharge
These steps are for clearing an applicator for service or
for storage near untrained persons. These instructions
presume that you have followed the steps at:
“Stopping Application” on page 76,
and the nurse tank is unhitched, per:
“Final Nurse Tank Unhitch” on page 79.
For a breakaway event, follow the instructions on
page 77 up through breakaway re-connection. Then
perform a normal shutdown (other than nurse tank
steps), per page 76.
The challenges in system discharge are:
• NH
3
liquid can remain in the system after the
recommended stopping procedures.
• NH
3
liquid self-cools as it evaporates, slowing
evaporation. It can take a long time for all of it to turn to
vapor, particularly in cooler weather.
• Once there is only vapor in the system, there is usually
little gas movement to drive the rest of it out.
• The tubing loops are usually the last to clear, and may
not fully clear. See sidebar.
Even if no ammonium hydroxide forms, the NH
3
vapor in
the system dilutes slowly with air. Harmless trace
amounts, noticed as occasional odor, may remain
indefinitely.
Normal Discharge
At the completion of stopping application and nurse tank
unhitching, all line valves are closed and all bleed valves
are open, and have been that way for at least an hour.
Transport may also have occurred, which aids clearing.
1.
Verify that all line valves are closed, and all bleed
valves open. If this is not the case, there is risk of
trapped ammonia. See “Clearing a Line Trap” on
page 108.
2.
Carefully walk down-wind of the applicator. Check for
ammonia odor. If pungent, there is at least some
pure NH
3
vapor in the system, and possibly some
liquid. Give the applicator some time to vent.
If there is no, or only mild odor, check the loops for
visible fluid. If only a few hours have elapsed since
application ended, this liquid is pure NH
3
. Stay away
until it has vaporized.
3.
From up-wind, check all the fittings and lines. If any
are cold (more than a few degrees below ambient
temperature), liquid evaporation is still in progress or
has only recently completed. Give the applicator
more time to vent.
Steps continue on next page...
Suffocation, Blinding, Burning, Freezing, Disabling and
Disfigurement Hazards:
Do not perform maintenance with anhydrous ammonia in the
system. Fully discharge the system of NH
3
liquid and vapor
before working on the applicator.
The delivery tubes are open to the atmosphere at the
knives or tines. When they don’t clear immediately, they
are likely to absorb atmospheric moisture, forming
ammonium hydroxide (NH
4
OH) in the tubes. This liquid
is highly caustic, and can persist for weeks or months,
but remains liquid at ambient temperatures, is harmless
to the tubing, and emits ammonia vapor slowly. If there
is liquid in the tubes, and it is not cold, it is likely to be an
NH
4
OH solution, and not pure NH
3
.
Figure 87
Delivery Loops
31617