Water quality monitoring

Water quality is a critical factor for trouble-free and safe operation of a steam boiler system.

It must be monitored in the following areas:

  • Boiler
  • Feed water
  • Make-up water
  • Condensate

This is why both continuous in-process checks and periodic inspections of the water quality at various points in the system are carried out:

  • In the boiler (via pH, conductivity and oxygen analysis)
  • In the feed water (via pH, conductivity and oxygen analysis)
  • In the make-up water (via analysis of silicic acid and continuous anaylsis of hardness)

Info on Equipment and control



When recirculating condensate, there is a danger of condensate which has become contaminated as a result of product ingress in the heat exchanger entering the steam boiler. This can cause considerable damage which can be prevented by monitoring the water quality. In doing so a distinction is made between substances:

  • that affect the electrical conductivity of the condensate and are monitored via conductivity electrodes
  • that cause cloudiness or light refraction which is monitored using what is referred to as a turbidity meter


Conductivity monitoring

Invasion of foreign matter in the condensate system that increases the conductivity can be quickly and reliably detected and signalled by a conductivity monitoring system (e.g. alkalis, acids, freshwater, water from boiling baths). Necessary measures are automatically introduced. These systems operate with automatic temperature compensation to ensure that temperature fluctuations do not lead to fault messages.

They are used in steam boiler systems, e.g. to monitor condensate or feed water.

If the conductivity in the condensate of roughly 50 µS/cm is exceeded, the condensate should be immediately discarded (e.g. via a three way valve). This excludes the possibility of contamination of the feed water, and subsequently also the steam boiler, before it enters the feed water vessel. The boiler operation itself therefore does not have to be interrupted and troubleshooting in the condensate system or heat exchangers can be carried out without any time pressure. However, it should be observed that the conductivity sensor detects all condensate flows.


Residual hardness monitoring

The softened water is monitored by a residual hardness monitoring device. Poor regeneration or overrunning of the water softener could lead to hardness invasion in the downstream system components. To prevent this the residual hardness is monitored either continuously or intermittently. If the limit of 0.01mmol/l is exceeded for a certain period, a fault display automatically appears in order to protect the downstream system components.


Turbidity monitoring

If there is also a danger of oil, grease or other emulsions finding their way into the condensate system, a turbidity monitoring system must be installed in addition to a conductivity monitoring system. The particle content of foreign matter is continuously monitored using optical measuring methods. Whenever possible, this should be installed upstream of the condensate tank as fresh steam or re-evaporation can affect the measurement.

If the set value is exceeded, it also makes sense to discard the condensate in this case until the turbidity falls below the set value once again.

Continuous water analysis

Smooth boiler operation depends on good water quality. The water analysis device measures and monitors the following parameters continuously:

  • pH value in the boiler water
  • pH value, oxygen content and conductivity in the boiler feed water
  • pH value and conductivity of the condensate or steam accumulator water content

All data is transferred to the System Control SCO via the bus system. All relevant water parameters, together with the boiler water conductivity and conductivities of the individual condensate flows, are therefore available in the System Control SCO. Demand-based control tasks can be carried out fully automatically. When defined limits are exceeded, all parameters are transferred to the fault memory of the System Control SCO of the plant control. The data can also be recorded continuously. This can be transferred via the bus system to a higher-level control system for further processing.

Functions of the water analyser are:

  • Stepless activation of the dosing system for oxygen binder
  • Stepless activation of the dosing system for alkalisation
  • Activation of exhaust vapour valve including display of saved exhaust vapour energy [kWh]
Water analyser WA

Water analyser WA

Schematic representation of operating principle of water treatment

Schematic representation of operating principle of water treatment

Water service module WSM-V


Boiler Control BCO


Softcontrol TH (optional)

Water analyser WA


System Control SCO


Water treatment module

Steam boiler 1


Chemical dosing


Steam boiler 2


Automation system


Product: Water analyser WA