Siemens SITRANS SL, Руководство по эксплуатации, Страница: 25 / 212

Description
2.5 Functional description
SITRANS SL
Operating Instructions, 12/2010, A5E01132948-04
27
Purging on process side
For purging on the process side, the flow of purging gas can be adjusted between 0 and
approx. 50 l/min at each sensor head using a needle valve (included in delivery).
Purging tubes
The purging media used on the process side flows through the purging tubes into the
process gas stream. The tubes extend into the process area by a few centimeters, usually
perpendicular to the process gas stream. The effective measuring path in the process gas is
defined as the distance between the ends of the two purging tubes. The standard length of
the purging tubes is 340 mm. To enable sufficient pivoting, the process wall should be max.
150 mm thick.
O
①
Purging tube
②
Process wall
l Path length
Figure 2-10 Measurement of the optical path length between the ends of the purging gas tubes
Purging on sensor side
Purging of sensors is always required for applications with oxygen as gas to be measured.
The sensors are then continuously purged with nitrogen. The flow of purging gas required in
this case is stated in the Technical data (Page 181).