Great Plains NP4000B Operator Manual - Manual (Page 122)

118 2013+ NP4000/A/B Table of Contents Index Great Plains Manufacturing, Inc.
417-199M Table of Contents Index 2014-05-14
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:
“NH3: Stopping Application” on page 70,
and the nurse tank is unhitched, per:
“NH3: Final Nurse Tank Unhitch” on page 73.
For a breakaway event, follow the instructions on
page 71 up through breakaway re-connection. Then
perform a normal shutdown (other than nurse tank
steps), per page 70.
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 delivery 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 116.
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 delivery
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
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 79
Delivery Loops
34983