Siemens SITRANS LG270 Operating Instructions Manual page 17

Steam boiler applications
Length - Reference dis-
tance (7)
260 mm (10.24 in)
500 mm (19.69 in)
750 mm (29.53 in)
PBD-51041071
Fig. 7: Mounting the instrument on insulated vessels.
1 Temperature insulation
2 Ambient temperature on the housing
Vapours, superimposed gases, high pressures and temperature dif-
ferences can change the spreading speed of radar impulses.
There are two possibilities to correct these deviations.
Corrective value in the process control system
In the technical data under "Influence of superimposed gas and pres-
sure on accuracy" you can find a table with deviation values in some
typical gases or in steam.
In the control system (DCS) you can correct the measurement results
of the SITRANS LG270 with these values.
The prerequisite is constant temperature and pressure in the vessel.
Automatic correction via the reference distance
The SITRANS LG270 can be equipped optionally with a running time
correction via reference distance. The probe can carry out an auto-
matic running time correction with it.
The reference distance can be overfilled. Make sure that the last
measured corrective value is used in case of overfilling.
Length - Blocking dis-
tance (4)
450 mm (17.72 in)
690 mm (27.17 in)
940 mm (37.01 in)
SITRANS LG270 - Operating Instructions
2
Probe length min. (2)
> 1000 mm (39.37 in)
> 1250 mm (49.21 in)
> 1500 mm (59.06 in)
1
Deviation max.
± 10 %
± 5 %
± 3 %
17