Cold Box
The helium liquefier / refrigerator cold
box is a Cryogenic Consultants, Inc. CCI
Model 300 JPS with the optional wet
engine module. The cold box was
manufactured by Meyer Tool&
Manufacturing Incorporated, Oak Lawn,
Illinois. The cold box is designed to
produce 400 watts refrigeration at 4.5 K
or 100 liters of liquid helium per hour
from warm helium gas. Liquid nitrogen is
supplied to the cold box as a
pre-coolant. Liquid nitrogen consumption
is rated at 0.7 liters of liquid
nitrogen per liter of liquid helium
produced.
Photo 1 - CCI Cold Box
The ‘cold box' is a super insulated,
vacuum jacketed component containing the
heat exchangers, extended stem cryogenic
valves, expansion (JT) valve and a
piston type expansion engine. Helium
gas, compressed to265 PSIG, enters the
cold box at near room temperature and is
cooled with liquid nitrogen and low
pressure helium gas. The high pressure
helium is further cooled by the cold
helium gas exiting the piston expansion
engine. This low press cold gas is
produced when a portion of the high
pressure gas stream expands in the
cylinder of the "piston type" expansion
engine. The remaining high pressure
helium gas travels to a JT expansion
valve or a wet expansion engine where
the temperature of the gas is reduced to
the liquefaction temperature of helium.
The liquefied helium exiting the JT
valve or wet expansion engine is
transferred to the liquid helium dewar
through bayoneted vacuum jacketed
transfer tubes. A small portion of the
helium returns as cold helium gas to the
cold box to be used to cool the high
pressure helium gas stream.
Photo 2 - Modified Control Panel
Controls
The system is controlled with pneumatic
actuators and controllers. However the
helium suction pressure incorporates a
duel output PID controller and two I/P
transducer controlled pneumatic actuated
valves to supply helium make up gas or
remove excess helium in the suction
manifold. A common problem associated
with pneumatic controls is the internal
corrosion created by moisture carried in
with the instrument air. Rather than
using compressed air, this system has
been operated from the boil off nitrogen
gas created in the liquid nitrogen
storage tank. As a result, the
controllers and actuators are clean and
corrosion free.
Helium Gas Management Rack
The helium gas management rack consists
of three pneumatically controlled valves
used to maintain compressor discharge
and suction pressures. The valves are
compressor discharge or "by-pass valve",
suction make up and suction withdraw
valves.
Photo 3 - Gas Management Rack
The system
includes:
The helium
refrigerator / liquefier system is currently installed
in an air conditioned building and operational.component
summary .
The super fluid helium system
consists of a heat exchanger module,
three vacuum pumping systems and all
interconnecting stainless steel piping,
flanged bellows and valves.
Specs can be
found:
