Taylor-Wharton RS-234 - Manual (Page 8)

7
OPERATION
The HOSPITAL RESERVE tank is designed to store liquefied gas and can deliver either liquid or gas. An external
vaporizer must be used to dispense gas. The following component and piping descriptions are pertinent to the
operation of the container and should be understood before attempting operation. The components may be identified
using the General Arrangement drawings located in the Appendix of this manual.
Component Description
LIQUID WITHDRAWAL Valve (V-2) - Liquid product is withdrawn from the container through the connection
controlled by this valve. The valve is opened for liquid withdrawal after properly connecting to a LIQUID supply line
connection.
LIQUID TOP FILL Valve (V-3) - Liquid product is added to the container through the connection controlled by this
valve.
FULL TRYCOCK & VENT Valve (V-9) - This valve controls a line into the head space of the container. It is used
during the fill process to vent the head space area while liquid is filling the inner container through the LIQUID TOP
FILL (V-3) valve.
PRESSURE GAUGE (G-1) - The pressure gauge displays the internal container pressure.
DIFFERENTIAL PRESSURE GAUGE (LL-2) - The container contents gauge indicates the product level in the
tank. This gauge is a differential pressure gauge calibrated in inches-of-water.
Economizer - An economizer circuit withdraws gas preferentially from the head space over the liquid in the container
-- gas that would otherwise be lost to venting. Excess pressure in the head space of the container is relieved by
allowing gas to flow from this area directly to the vaporizer while product is being withdrawn from the container.
Normal operating pressure is preserved to ensure uninterrupted product delivery. This is controlled by the
ECONOMIZER REGULATOR (R-2). The economizer is automatic and requires no operator attention. The outlet of
the economizer regulator must be piped to the VAPORIZER INLET in order for the circuit to function in this manner.
The economizer may also be used to quietly vent excess pressure to atmosphere without lifting the SAFETY VALVES
(SV-1 & SV-2). See the section below titled, “Withdrawing Product from the Container”.
TANK SAFETY DEVICES - This tank has dual inner container relief devices with a DIVERTER VALVE (V-1) to
allow a reserve set of safety devices to be switched into service while the other is repaired. Each set consists of a
primary relief valve to relieve container pressure when it exceeds a preset point. The valve resets when pressure drops
below this point. In addition, each primary relief valve is backed-up by a secondary relief device which consists of a
rupture disc that will burst at a pressure value that is greater than the primary relief valve setpoint.
The INNER VESSEL SAFETY VALVES (SV-1 & 2) automatically relieve tank pressure when the maximum
allowable working pressure of the tank is reached. The INNER RUPTURE DISCS (BD-1 & 2) are the secondary relief
devices that rupture and require replacement of inserts in the event a safety valve malfunctions and allows tank
pressure to reach the burst pressure rating. Like the primary relief valves, one rupture disc is in service while the other
is in reserve.
Overpressure of the annular space of the container is protected by an ANNULAR RUPTURE DISC (BD-3).
Pressure Building - A Pressure Building circuit is used to ensure sufficient driving pressure during high product
withdrawal periods. This function is actuated by opening a valve that creates a path from the liquid in the bottom of the
container to the gas space in the top. This path contains a pressure building coil to vaporize product as it migrates from