Endress+Hauser Liquiline CM44P - Page 121

Liquiline CM44P Operation
Endress+Hauser 121
Calculated pH value
The pH value can be calculated from the measured values of two conductivity sensors
under certain conditions. Areas of application include power stations, steam generators
and boiler feedwater.
Menu/Setup/Additional functions/Mathematical functions/MF1 to 8/Mode = pH calculation from
conductivity
Function Options Info
Calculation Selection
• Off
• On
Factory setting
Off
On/off switch for the function
Method Selection
• NaOH
• NH3
• LiOH
Factory setting
NaOH
The calculation is performed on the basis of
Guideline VGB‐R‐450L of the Technical
Association of Large Power Plant Operators
(Verband der Großkesselbetreiber, (VGB)).
NaOH
pH = 11 + log {(κ
v
- 1/3 κ
h
)/273}
NH3
pH = 11 + log {(κ
v
- 1/3 κ
h
)/243}
LiOH
pH = 11 + log {(κ
v
- 1/3 κ
h
)/228}
κ
v
... Inlet ... direct conductivity
κ
h
... Outlet ... acid conductivity
Inlet The options depend on the
sensors connected
Inlet
Sensor upstream from the cation exchanger,
"direct conductivity"
Outlet
Sensor downstream from the cation exchanger,
"acid conductivity"
Selection of the measured value is obsolete as it
must always be Conductivity.
Measured value
Outlet
Measured value
Calculated pH Read only View this value in a user-defined measuring
screen or output the value via the current output.
Mathematical function
assignment view
Overview of the configured functions
Cation exchanger capacity (optional, with activation code)
Cation exchangers are used to monitor the water/steam circuit for inorganic
contamination. The cation exchangers eliminate the disruptive influence of alkalizing
agents, such as ammonium hydroxide or caustic soda, which are added to the boiler
feedwater.
The service life of cation exchangers depends on:
• The type of alkalizing agent
• The concentration of the alkalizing agent
• The amount of contamination in the medium
• The capacity of the cation exchanger (efficiency of the resin)
To ensure the smooth operation of power stations, it is important to continuously monitor
the exchange column load. When a user-defined remaining capacity is reached, the
transmitter displays a diagnostic message so that the ion exchange column can be replaced
or regenerated in good time.