Taylor-Wharton VJ Bulk Tank - Manual (Page 14)

maintained above this value to insure solid CO2 will not form inside the container.
Before performing maintenance, components must be isolated and depressurized, or
the contents must be transferred to another container so that the container pressure
can be released. In addition to avoid irreparable damage to the structure of the tank,
an internal tank pressure of no less than 200 PSIG (14 bar/1379 kPa) must be
maintained at all times.
LEAK TEST
After making repairs requiring disassembly or replacement, leak test all valves or piping joints that
were taken apart and reconnected. Apply leak detector to the test surface per the component
manufacturer's instructions. Large leaks instantly form large bubble clusters, while fine leaks
produce white foam that builds up more slowly. All leaks must be repaired and re-tested before the
tank is returned to service.
HAND VALVES
The most common trouble with manual valves will be leakage at the stem packing. Packing leaks are
usually indicated by ice emerging from the packing gland or retainer threads. If packing leakage
cannot be stopped by tightening, replace packing. Use pre-formed packing that can be ordered from
the valve manufacturer.
BACK PRESSURE VALVE
Before attempting repair of the BACK PRESSURE VALVE (PCV), isolate and depressurize the
valve and associated piping.
RESETTING BACK PRESSURE VALVE
1.
Open BACKPRESSURE REGULATOR ISOLATION VALVE (V-8) and loosen Back
Pressure Valve pressure screw lock nut and turn pressure screw in (clockwise) to end of
adjustment range.
2.
a. If tank pressure is below desired setpoint: Build pressure within tank using a pressure
building unit. As tank pressure increases to desired setpoint, approx. 10 psi (7 bar/70 kPa)
below setting of SAFETY VALVES (SV-1A/B) discontinue pressure building.
b. If tank pressure is above desired setpoint: Open EQUALIZATION VALVE (V-2) and vent
until tank pressure is at desired setpoint, approx. 10 psi (7 bar/70 kPa) below setting of
SAFETY VALVES (SV-1A/B).
3.
With tank pressure at desired BACK PRESSURE REGULATOR (PCV) setpoint, slowly turn
pressure screw out (counterclockwise) until valve just opens. Tighten pressure screw lock
nut.
PRESSURE AND LIQUID LEVEL GAUGES
The major cause of a malfunctioning tank PRESSURE GAUGE (PI) or LIQUID LEVEL GAUGE
(LI) is an open INSTRUMENT EQUALIZATION VALVE (V-7) or leakage in the gauge lines.
14