5-2
180 liter LN2 Supply Tank
Thermo Scientific
Section 5
Troubleshooting
(continued)
Problem
Problem Cause
Corrective Action
Liquid cylinder builds
excessive pressure or
builds pressure too fast.
Frost occurs around the
circumference of the
shell 4" to 8" (10.2 to
20.4 cm) from the floor.
Frost occurs around the
circumference of the
shell 10" (25.4 cm)from
the floor and up. Frost
spot spirals up the shell.
Low usage.
Cylinder is over filled.
Vacuum is deteriorating.
Cylinder is leaking.
Frost is residual from last
fill or earlier use.
Cylinder is vaporizing
liquid into gas.
If daily gas usage is under 100 SCF (2.8 NM3), the
cylinder will build pressure. In liquid service, the cylin-
der should be equipped with low pressure relief valve
and regulator. Normal pressure rise should not be
more than 50 psi (3.4 BAR)per day.
If the cylinder is filled past the vent trycock or past the
DOT specified fill weight, the pressure may rise rapidly
after a fill.
This can be accompanied by cold or frost occurring
evenly over the cylinder surface. Refer to the trouble-
shooting section on frost.
Check for frost on lines or on top of head. Listen for
hissing, soap test joints for leaks. Isolate leak and call
MVE for repair details.
This is normal. A ring of ice or an oval shaped ice ball
often remains on the cylinder for days after the last
use or fill.
This is normal. The frost should melt within two hours
after the gas use stops
Liquid cylinder pressure
is too low.
Usage is too high.
Refer to Specifications for maximum recommended
delivery rates.
