Procedure:
UNLOADING A TANK CAR
Facility:
Step
1
2
3
4
5
6
13
14
15
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Last Revised:
Operational Procedures
Consequence of Deviation
Safety First. Check to make sure the safety water tank is full of clean
water. Set brakes, chock wheels, and set the “Stop-Tank Car Connected”
signs on the track at least 25 feet from the end of the car nearest the
switch. Put on protective gloves and safety goggles.
Connect all vapor and liquid hoses. Remover plugs or caps from valve
openings. Clean threads. Apply pipe compound. Start nipples straight.
Hand tighten first, then finish tightening with a wrench. Connect liquid
hoses to liquid valve nipples and the vapor hose to the vapor valve nipple
of the tank car.
Close all bleeder valves in the vapor and liquid hose connectors.
Close pressure conditions and check to see that all valves are set for
unloading the tank car. If the pressure is higher in the storage tank than
in the tank car (Reverse Flow Condition), open the vapor valves, set the
four-way valve for loading the storage tank (Neutral condition), open the
intervening vapor valves, set the four-way valve for loading the storage
tank, and start the compressor
Open the liquid valves slowly. Check the gauge pressure of the tank car
and the storage tank. If the pressure is higher in the tank car than in the
storage tank (Forward Flow condition), slowly open the intervening
liquid valves, set the four-way valve for loading the storage tank and
allow liquid the liquid to flow from the tank car to the storage tank.
When the pressure in the tank car is only 5 to 10 psig higher than the
pressure in the storage tank, slowly open the vapor valves and start the
compressor.
Check liquid levels by observing the gauges on the storage tank. Don’t
overfill the storage tank. Don’t try to unload the ammonia too fast or the
excess flow valves in the tank car will close and stop the flow of liquid.
If this should happen, stop the compressor and close the liquid valves
have again opened. Then open the liquid valves slowly and continue
unloading the tank car.
Monitor Filling! Monitor the liquid level gauge on top of the nurse tank
until it reads 85% or until liquid ammonia begins to spit out the 85%
vapor valve at which time the nurse tank is full.
Alert! When filling the last nurse tank, turn off compressor by
depressing the stop button located in the switchbox mounted on the loadout riser and close the orange liquid and yellow vapor valves on the loadout riser by turning knobs clockwise until fully closed, do not wrench. If
other nurse tanks are filling at the riser, skip this step and proceed to Step
15.
Close Hose-end Valves! Close the orange liquid hose-end valve by
depressing the release button with one hand and pulling the lever down
Overfilling the nurse tank
could result in a PRV release
or tank rupture.
Failure to shut off
compressor after filling last
nurse tank could result in
over pressuring piping.
All valves must be closed
before disconnecting nurse
Procedure:
Facility:
16
17
18
19
20
21
22
UNLOADING A TANK CAR
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with the other hand until it locks into its closed position. Close the
yellow vapor hose-end valve by turning clockwise until fully closed, do
not wrench.
Close Nurse Tank Valves! Close both the orange liquid and the yellow
vapor valves on the nurse tank by turning knobs clockwise until fully
closed, do not wrench.
Open Bleeder Valves! Standing upwind, bleed off nurse tank
connections by opening the orange liquid and the yellow vapor bleeder
valves by turning the knobs in a counter-clockwise direction. You will
hear a hissing sound. This may take a minute or two. When the hissing
sound stops, all pressure has been bled from the hose-end connections
and the valves can now be disconnected.
Disconnect Hoses! Disconnect the orange liquid and yellow vapor hoseend assemblies from the nurse tank and return them to their storage
positions.
Replace Dust Caps! Replace the dust caps on the orange liquid and
yellow vapor fill valves on the nurse tank.
Connect Nurse Tank! Reconnect hitch pin and safety chains to the tow
vehicle (be certain chains are crossed). Remove wheel chock.
Final Inspection! Inspect by walking around the nurse tank. Make sure
all hoses have been disconnected and return to their storage positions.
Depart! The nurse tank is ready to depart.
tank or connections will not
bleed down.
All valves must be closed
before disconnecting nurse
tank.
Failure to properly bleed-off
connections could result in
ammonia exposure when
disconnecting hose-end
assemblies.