System discharge, Normal discharge – Great Plains NH3 Safety User Manual
Page 43
Great Plains Manufacturing, Inc.
Ammonia Maintenance Safety
39
2013-07-15
407-551M
System Discharge
These steps are for clearing an implement for service or
for storage near untrained persons. These instructions
presume that you have followed the steps at:
“Stopping Application” on page 29,
and the nurse tank is unhitched, per:
“Final Nurse Tank Unhitch” on page 31.
For a breakaway event, follow the instructions on
page 33 up through breakaway re-connection. Then
perform a normal shutdown (other than nurse tank
steps), per page 29.
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 applicator 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 37.
2.
Carefully walk down-wind of the implement. Check
for ammonia odor. If pungent, there is at least some
pure NH
3
vapor in the system, and possibly some
liquid. Give the implement some time to vent.
If there is no, or only mild odor, check the applicator
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 implement
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 implement.
The applicator tubes are open to the atmosphere at the
tines or knives. 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 31
Applicator Loops
31617