
2019-04-12
417-459M
NP2540
Maintenance and Lubrication
116
Never open a closed valve in an enclosed area. In addition
to the exposure hazard, a release of
NH
3
could result in a
concentration level that is flammable or explosive.
Never point a closed valve at your face.
If replacing a ball valve, don’t just check that the new
valve is specified for
NH
3
service:
Replace orifice ball valves only with orifice ball valves.
Replace solid ball valves with orifice ball valves.
Install an orifice ball valve correctly. The orifice side
points down-stream (in the direction of flow).
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:
and the nurse tank is unhitched, per:
For a breakaway event, follow the instructions on
page 69 up through breakaway re-connection. Then
perform a normal shutdown (other than nurse tank
steps), per page 68.
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.
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
3
) 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
3
solution, and not pure NH
3
.