KROHNE BM 70 A_P EN - Manual (Page 27)

Installation and operating instructions BM 70 A/P Page: 27 11/00
6.3.3 Product limitations
Radar-based level measuring devices are not suitable for the following products:
•
liquid a mmonia (NH
3
)
•
liquid hydrogen (H
2
)
•
liquid helium (He)
6.3.4 Product temperature (unrestricted)
The product temperature is not a relevant factor, provided the ambient temperature (see 6.2.2) and
the flange temperature (see 6.2.3) are within the specified limits.
6.3.5 maximum allowable operating pressure (max. 64 bar / 928 psig)
Flange system with horn antenna or Wave-Guide:
PN 16 PN 25 PN 40 PN 64
DN 80 16 bar (232 psig) --- 40 bar (580 psig) 64 bar (928 psig)
DN 100 16 bar (232 psig) --- 38 bar (551 psig) 55 bar (798 psig)
DN 150 16 bar (232 psig) --- 34 bar (493 psig) 47 bar (682 psig)
DN 200 16 bar (232 psig) 25 bar (363 psig) 32 bar (464 psig) 45 bar (653 psig)
Information on higher pressures (up to 400 bar / 5800 psig) supplied on request
Wave-Stick without plate resp. LP flange system: max. 2 bar / 29 psig
Wave-Stick with plate: max. 16 bar, dependent on temperature:
Temperature T
Pressure
-20 +150 °C +100
-15
+15
232
(46 - 0.3·T[°C]) bar
-4 +302 °F +212
-1
+1
+16
bar psig
(740 - 2.4·T[°F]) psig
6.4 Maintenance
Cleaning the antenna
Particular process applications can cause severe contamination of the antenna. Microwaves cannot
be properly emitted or received when reflected from deposits on the antenna. In such cases, the
BM 70 A/P will usually indicate maximum level (volume) or minimum distance.
The level of contamination at which such errors occur depends firstly on the product concerned, and
secondly on the reflection index, which is mainly determined by the relative permittivity
ε
r.
Regular cleaning, or use of the purging device (see Sect. 6.1.7), is advisable if the product has a
tendency to form deposits, etc.
When spraying, washing down, or cleaning with mechanical aids, take special care not to damage
either the horn antenna or the bottom Teflon plug at the waveguide window (see Section 7.4 "Field
assembly of the BM 70 A/P"). If cleaning agents are used, take material resistance into account!