Taylor-Wharton VJ Series Tanks - Manual (Page 12)

12
OPERATION
Normal operation of a properly installed unit requires some operator intervention. Frequent checks
should be made to ensure pressure and liquid levels are within normal range. Low pressure could
cause damage to the tank due to resulting liquid temperature below the design parameters of the steel
in the pressure vessel. A daily inspection that includes checks for frost, leaks, low pressure, low
liquid level and physical damage is recommended.
PURGE PROCEDURE
Before placing a tank in service, determine the level of purity in the pressure vessel. If pressure
vessel contents purity is unacceptable, perform a product purge to reduce contaminants. The
following procedure is recommended for most application:
1.
Attach the transport vapor equalization line to CN-2. Product delivery pressure should be
around 250 psig (17.23 bar/1723 kPa).
CAUTION: A positive pressure must always be maintained in the tank during the purge
procedure to prevent drawing atmospheric contaminants back into the tank.
2.
Close all valves except ISOLATION VALVES (V-5, V-6).
3.
Remove cap from FILL CONNECTION (CN-1), then open LIQUID FILL VALVE (V-1) and
vent inner vessel to 5 psig (0.34 bar/34 kPa) as indicated on the tank PRESSURE GAUGE,
INNER VESSEL (PI). Close LIQUID FILL VALVE (V-1).
4.
Open VAPOR EQUALIZATION VALVE (V-2) slightly to allow vapor to flow slowly from
the transport into top of the tank. Flow must be gradual enough to allow the vapor to warm in
the tank and to allow the transport pressure building system to keep the transport pressure
stable.
5.
When tank PRESSURE INDICATOR, INNER VESSEL (PI) indicates maximum desired
purge pressure, close the vapor supply source.
6.
Close LIQUID AND VAPOR ISOLATION VALVES (V-6, V-5). The EQUALIZATION
VALVE (V-7) should be opened just before closing ISOLATION VALVES (V-6, V-5) to
prevent damage to the LIQUID LEVEL GAUGE (LI). Carefully loosen the adapters on both
sides of the LIQUID LEVEL GAUGE (LI) to relieve pressure. Disconnect the instrument
lines and fully open ISOLATION VALVES (V-6, V-5). Visually check the resultant gas
streams for signs of moisture. Vent lines for approximately two minutes. If no moisture is
evident, close the ISOLATION VALVES (V-6, V-5). If moisture is evident, continue venting
until the stream is free of moisture.
CAUTION: Do not look directly into the tank lines. Bodily injury could occur. Carefully
open gauge valves since some residual liquid may have remained in tank or the
instrument lines.
7.
Open DRAIN VALVE (V-9A) to check for moisture as in Step 8.