MVE LN2 Tx, Operator'S Manual, Page: 3 / 9

PN 15098830 Rev A — 3
General
The MVE LN2 TX (Liquid Nitrogen Transfer system) is a system
that allows liquid nitrogen (LN2) to be drawn out of an open
container and transferred to another open container.
It can be employed to remove liquid from a freezer to facilitate
servicing, or to remove excess liquid from a dry shipper after
charging.
System Description
The MVE LN2 TX uses a high velocity nitrogen gas stream to
create suction (vacuum) at the inlet that draws liquid up into the
transfer device. Once the liquid is drawn into the gas stream, the
liquid is pushed through the transfer tube and hose by the gas
stream.
The high velocity nitrogen gas is discharged through annular
orifices around the ID of the suction head that are directed toward
the outlet of the suction head into the transfer tube. The use of
suction from the far end of a hose to draw LN2 from a container
results in the liquid flashing to gas. The liquid may be removed
from a container, but is not conserved. The placement of the
suction head at the inlet end of the system minimizes the low
pressure (vacuum) area in the transfer system, thus minimizing
flash loss. Once the liquid is entrained in the gas stream, it is re-
pressurized to further minimize flash loss.
N2 Gas Connection
LN2 Outlet
Flex Transfer Hose
LN2 Inlet (Vacuum)
Figure 1: LN2 Tx
HANDLING OF LIQUID
NITROGEN
GENERAL
Liquid Nitrogen (LN2) is used in the operation of the MVE LN2
TX. Although not explosive, there are a number of safety consid-
erations to keep in mind in the handling of LN2.
PROPERTIES
Nitrogen is a colorless, odorless, tasteless gas. Gaseous Nitrogen
makes up about 78% of the Earth’s atmosphere. Once collected
and isolated, Nitrogen will liquefy when cooled properly. The
properties of LN2 are as follows:
PROPERTY VALUE
Boiling Point @ 1 ATM, in °C ...........................-195.8
Thermal Conductivity (Gas), w/m2 °K ............0.079
Latent Heat of Vaporization, Btu/Liter ............152.0
Liquid Density, lb/liter @ 1 ATM .....................1.782
Expansion Ratio @ STP .....................................746:1
HANDLING
CRYOGENIC
STORAGE DEWARS
Cryogenic containers (Dewar’s) must be operated in accordance
with the manufacturer’s instructions. Safety instructions will also
be posted on the side of each Dewar. Cryogenic Dewars must be
kept in a well-ventilated place where they are protected from the
weather and away from any sources of heat. A typical cryogenic
Dewar is shown in Figure 2.
Figure 2: Typical Cryogenic Dewar