Teledyne LGA-3500 - Laser Gas Analysis system - Manual (Page 32)

Installation Model 3500
Teledyne Analytical Instruments 18
designed without a power switch. A separate wall mountable enclosure
is supplied for housing the power supply and switches.
CAUTION: DO NOT DISCONNECT THE CABLE BETWEEN THE
CENTRAL PROCESSING UNIT, THE TRANSMITTER
UNIT AND THE RECEIVER UNIT WHEN THE POWER
SUPPLY IS ON. THIS COULD CAUSE DAMAGE TO
THE LASER.
3.5 Purge System Installation
If dust or other pollutant concentration is relatively high in the
environment under test, a purging system must be installed to protect the
optical devices in the transmitter and receiver units.
In a typical purging system, the purge gas is directed through the
inside of the instrument flange, the welding flange or a special purging
pipe, and into the gas flow pipe. The purging gas forms an air wall to
protect the optical devices. The purge flow required depends on the
process environment.
Usually, a purge gas flow rate in the range of 5-50
L/min×2 is required.
Compressed air or nitrogen is the most frequently used purging gas
sources. A filter should be installed to remove dust, water and oil
droplets larger than 1 micron in size before entering the system to
prevent the purge gas from contaminating the optical devices,. TAI
provides a range of purge systems for various applications and most are
equipped with appropriate filters. Please contact technical support if
your application requires a purge system.
A typical purge system is shown in Figure 3.6. This unit uses
compressed air (or nitrogen) as the purge gas and includes a 1 micron
filter. Two needle valves and flowmeters are installed to monitor and
control the purge rate to the transmitter and receiver. The housing is
equipped with a window for visual access while the housing door is
sealed.
To install the purge unit, connect each gas outlet of the purge
system to a purge inlet on the instrument flanges. Connect the inlet to a
suitable purge gas supply. A regulator should be used to control the
pressure to the purge system. The gas pressure depends on the particular
purge system installed and will be noted on the unit.