0397024 JOHNSON CYLINDER & C'CASE ASSY.

Nitrogen used in this process exceeds 57° C (135° F) temperature and 6.9 bar (100 psi) pressure. There is a potential for burn hazard if proper procedure is not followed. Gloves and Eye protection are required during this procedure and once the discharge has started do not touch the components with a bare hand.
Do not allow dirt to enter the fuel system. Thoroughly clean the area around a fuel system component that will be disconnected. Fit a suitable cover over any disconnected fuel system components.
Nitrogen from a liquid cylinder or compressed gas cylinder is the recommended purge gas. Use a compressed gas pressure regulator to reduce the pressure from the nitrogen gas source to approximately 345 kPa (50 psi).Specifications
Table 1
Parameter Value
Dew Point −40° C (−40° F)
Level sensor 498+/-20 pF Introduction
This procedure is used for drying moisture/water out of an empty Liquid Natural Gas (LNG) tank. If any of the plumbing components needs to be removed or changed, the plumbing must be opened and this allows the moist atmosphere to enter the LNG tank. Moisture in the LNG tank can cause several issues. One concern is that the moisture can cause error in the LNG level sensing. Due to the nature of the level sensor moisture causes the reading to be high and give the appearance of LNG in the tank when there is none. Another concern for moisture in the LNG tank is that if the moisture freezes the moisture can cause a blockage and restrict LNG flow out of the tank.This procedure utilizes heated nitrogen to dry out the LNG tank. The nitrogen runs through a heater at low pressure and gets heated. The heated nitrogen then goes right into the inner tank to begin thoroughly heating the inner tank and inner tank components. Once the inner tank and internal components gets to water boiling temperature, the water/moisture is displaced by the hot nitrogen and forced out of the tank. The dryness of the tank is verified using a dew point meter to assure confidence.Personal Protective Equipment
Leather work gloves
Safety glasses (with side shields)
Steel toe bootsRequired Tools
Table 2
Required Tools Qty
BAK Type S36 Heater 1
Keysight Technologies U1733C LCR Meter 1
Traceable Hygrometer Thermometer Dew Point Meter Model 4085CC 1
Compressed Nitrogen 1
JC Carter Vent Nozzle 662600-1 1
Heater nozzle to JIC adapter (7/8” ID pip to 1” JIC) 1 Test Preparation
Before starting procedure check valve positions to ensure proper drying:
Valve 1: Closed
Valve 2: Closed
Valve 5: Closed
Valve 6: Closed
Valve 9: Closed
Illustration 1 g06312072
Depressurize/Empty LNG tank completely by opening tank isolation valve "Valve Tag 2". Close valve once the tank has no pressure left.Note: Stand clear of outlet port, tank will depressurize through this valve.
Illustration 2 g06312074
Check capacitance of LNG tank with the LCR meter, before drying process for a baseline reference.
Plug in leads to LCR meter and zero leads by depressing the "Null/Cal" button.
Then long hold the "Range/Auto" button until auto function is activated
Note the capacitance reading and units.
Disconnect the LCR meter.
Remove the inlet line that contains the SV2 for the heated air enter the tank with minimal back pressure. Set aside the section with SV2 and cap the ends to prevent debris and moisture from getting into section that was removed.
Illustration 3 g06312078
(1) Heater nozzle (outlet)
Illustration 4 g06312085
Add the valve to inlet port for isolation. Plumb the heater into the tank inlet port upstream from the valve.
Make sure that the heater is set to 0 until ready to heat the nitrogen.
Illustration 5 g06312087
Plumb the nitrogen into the back of the heater.
Make sure the valves "1, 2, 5, 6, and 9" are closed.Test Procedure