Flowserve LRG 16-40 - Manual (Page 5)

5
Explanatory Notes
Scope of supply
LRG 16-40
Level electrode type LRG 6-40
S. S. joint ring ∅ 33 x 39, form D, DIN 7603 (made of .430), bright annealed
Terminating resistor 0 Ω
Installation manual
LRG 17-40
Level electrode type LRG 7-40
S. S. joint ring ∅ 33 x 39, form D, DIN 7603 (made of .430), bright annealed
Terminating resistor 0 Ω
Installation manual
Description
The conductivity electrode LRG x-40 consists of a TDS (= Total Dissolved Solids) monitoring electrode
for conductivity measurement, a temperature sensor for detecting the fluid temperature and a conduc-
tivity transmitter that is fully integrated in the terminal box.
The equipment is of the two electrode type and works according to the conductometric measurement
principle, measuring the electrical conductivity of electrically conductive fluids.
Together with the TDS controller LRR -40 and an operating device type URB or SPECTORcontrol
the conductivity electrode LRG x-40 can be used as conductivity limiter and continuous blowdown
controller in steam boilers and (pressurized) hot water plants.
The data exchange between the conductivity electrode LRG x-40, the control and operating equip-
ment and other devices is effected by the CAN-Bus to ISO 898, using the CANopen protocols.
Function
A measuring current of variable frequency flows through the fluid and creates a potential gradient
between the measuring electrode and the measuring tube. The potential gradient is evaluated as
measuring voltage U
U
.
The electrical conductivity is a function of temperature. To relate the measured values to a reference
temperature the resistance thermometer integrated in the electrode measures the fluid temperature.
The electrical conductivity is calculated from the measuring voltages U
U
and U
I
and – through
temperature compensation – is based on a reference temperature of 5°C.
The electrical conductivity is a non-linear function of temperature. For the compensation of the
measured values one of the following three procedures can be applied:
n
Temperature compensation Auto: The conductivity electrode records the specific conductivity/
temperature curve of the respective fluid and based on the data obtained, performs the compen-
sation.
The auto-curve temperature compensation is suitable for boilers operating with variable pressure,
which means that the boiler does not have a fixed working pressure (e. g. low load 0 bar, full load
5 bar). The system detects in steps of 0°C all temperatures and conductivity values from 00°C
to the service temperature. For this purpose the boiler must reach its working pressure (with variable
pressure operation: max. allowable working pressure). If the standard curve is not suitable for variable
pressure operation, use can be made of the recorded curve.