1-6
Chapter 1: Preparing the Installation
42/24-10 EN Rev. 9
Purge Gas for Housing Purge
Purge Gas
The following purge gases can be used:
•
Nitrogen when measuring flammable gases or
•
Instrument air when measuring corrosive gases (quality per ISO 8573-1 Class 3,
i.e. max. particle size of 40
μ
m, max. oil content 1 mg/m
3
, max. pressure dew
point +3 °C).
For the Limas11 and Uras26 analyzer modules the purge gas should not contain
any sample gas components. Any sample components in the purge gas can
cause false readings.
Purge Gas Flow Rate
during Initial Purge
The purge gas flow and the duration of the purge process depend on the volume
to be purged (see the following table). If the purge gas flow rate is lower than
indicated the duration of the process must be increased correspondingly.
Volume to be Purged
Purge Gas Flow Rate
Duration
Gas Path
100 l/h (max.)
approx. 20 sec.
Central Unit with or without
Analyzer Module
200 l/h (max.)
approx. 1 hr.
Analyzer separately: Caldos25,
Caldos27, Magnos206, Magnos27
200 l/h (max.)
approx. 3 min.
Purge Gas Flow Rate
during Operation
Purge gas flow rate at device inlet max. 20 l/h (constant)
Purge gas positive pressure p
e
= 2 to 4 hPa
•
Because of leakage losses the purge gas flow rate at the device output is
approx. 5 to 10 l/h for a purge gas flow rate at the device inlet of 20 l/h.
•
Notes for selection and use of flow meters:
•
Measuring range 7 to 70 l/h
•
Pressure drop < 4 hPa
•
Needle valve open
•
Recommendation: Flow meter 7 to 70 l/h, Catalog No. 23151-5-8018474
CAUTION!
Purge gas can escape from the housing if there are any leak points. When
using nitrogen as the purge gas, take all required precautions against
suffocation.
CAUTION!
Purge gas flow must always be restricted upstream of the purge gas inlet!
If the purge gas flow is restricted after the purge gas outlet, the housing
seals are subjected to full purge gas pressure which can result in damage
to the keypad!