Endress+Hauser MODBUS RS485 Operating Instructions Manual page 14

Installation
"
14
Partially filled pipes
Partially filled pipes with gradients necessitate a drain-type configuration. The Empty Pipe Detection
function offers additional protection by detecting empty or partially filled pipes → ä 91.
Caution!
Risk of solids accumulating. Do not install the sensor at the lowest point in the drain. It is advisable
to install a cleaning valve.
Fig. 8: Installation in partially filled pipe
Down pipes
Install a siphon or a vent valve downstream of the sensor in down pipes longer than 5 meters
(16,3 ft). This precaution is to avoid low pressure and the consequent risk of damage to the lining
of the measuring tube. This measure also prevents the system losing prime, which could cause air
inclusions.
Information on the lining's resistance to partial vacuum → ä 123
Fig. 9: Measures for installation in a down pipe
1 Vent valve
2 Siphon
Length of down pipe (h ≥ 5 m (16,3 ft)
h
Proline Promag 53 MODBUS RS485
³ 2 x DN
³ 5 x DN
1
2
A0011901
A0011902
Endress+Hauser