Installation Guide

Don’t install the vapor quality sensor
on the top of a riser.
In a part load situation, the gas velocity
will not be sufficient to carry the liquid
upwards. This means the sensor will
measure dry gas, but the sensor will
not be able to see the difference
between a riser filled with liquid and a
dry riser. When the liquid feed is
controlled based on this measurement
you will end up with a system blocked
by liquid
When installed
just after the
evaporator the
sensor can be
used to control
the liquid feed
and secure a
riser which is
working
If you install a drop leg
after the sensor you
protect it against liquid
trapped in the sensor
when the system is
stopped.
This is important for DX
systems, but can be
skipped in overfeed
systems
Where to install the vapor quality sensor?
The vapor quality sensor detects the liquid content in the output from an evaporator. This
output is used for controlling the liquid feed and securing a constant dryness. The sensor is used
both in overfeed systems and in DX systems - just with different targets for the liquid content.
The vapor quality sensor can have different shapes, but for all it is important to install it as close
to the evaporator as possible to get the best feedback for the control system.
In this DX blast freezer, the
vapor quality sensor is installed
just before the riser