Key Parameters Monitored by SWAS Panels
Prosoft Engineering
Technical Compliance Specialist
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Primary Keyword: SWAS Panel
Secondary Keywords: SWAS Panel Maintenance, Online SWAS Panel, SWAS Panel India
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Introduction
In thermal power plants, combined-cycle power plants, captive power plants, industrial boilers, sugar mills, paper mills, chemical plants and other steam-generation facilities, maintaining the correct steam and water chemistry is essential for reliable operation.
A SWAS Panel (Steam and Water Analysis System) provides continuous monitoring of critical chemical and physical parameters in boiler feedwater, condensate, boiler drum water, steam and other water/steam circuits.
The parameters selected for a SWAS Panel depend on the plant design, boiler pressure, water-treatment philosophy, materials of construction, steam cycle and OEM chemistry requirements. Common measurements include conductivity, cation conductivity, pH, dissolved oxygen, silica, sodium and phosphate, along with sample temperature, pressure and flow.
A properly designed Online SWAS Panel combines sample extraction, pressure reduction, cooling, filtration, flow control and online analyzers so that the sample reaching each analyzer is representative and within its specified operating conditions.
What Is a SWAS Panel?
A SWAS Panel is an integrated sampling and analytical system used to monitor the chemistry of steam and water circuits.
A typical system may contain:
Sample isolation valves
Pressure-reducing valves
Sample coolers
Temperature sensors
Pressure gauges/transmitters
Flowmeters
Flow-control valves
Filters
Conductivity analyzers
pH analyzers
Dissolved oxygen analyzers
Silica analyzers
Sodium analyzers
Phosphate analyzers
Cation conductivity systems
Sample distribution manifolds
Drain systems
PLC/HMI
Communication interfaces for DCS/SCADA
The SWAS panel therefore should not be considered simply an analyzer cabinet. It is a complete sample-conditioning and measurement system.
Why Are SWAS Parameters Important?
Steam and water chemistry can directly affect:
Boiler reliability
Turbine performance
Heat-transfer surfaces
Condenser performance
Feedwater systems
Economizers
Superheaters
Reheaters
HRSG systems
Corrosion rates
Scale and deposit formation
Steam purity
Small changes in ionic contamination or dissolved gases can sometimes provide an early indication of condenser leakage, contamination, corrosion or problems with water-treatment systems.
Continuous monitoring allows operators to identify these changes much earlier than periodic laboratory testing alone.
Key Parameters Monitored by SWAS Panels
1. Specific Conductivity
Specific conductivity is one of the most commonly monitored parameters in a SWAS system.
It indicates the ability of the water sample to conduct electrical current, which is related to the concentration of dissolved ionic species.
Why monitor conductivity?
A rise in conductivity can indicate:
Ionic contamination
Cooling-water ingress
Chemical dosing changes
Make-up water contamination
Treatment-system problems
Condenser leakage
Process contamination
Conductivity is generally measured using a conductivity cell and temperature compensation.
Typical applications
Conductivity monitoring can be applied to:
Feedwater
Condensate
Boiler water
Make-up water
Steam condensate
Actual alarm limits should be established according to the plant chemistry program and applicable equipment/OEM requirements.
2. Cation Conductivity
Cation conductivity is particularly important in power-cycle chemistry monitoring.
In this measurement, the sample passes through a cation exchange medium before conductivity is measured. The exchange process helps make certain anionic contaminants more apparent.
Cation conductivity can be useful for detecting contamination associated with:
Chlorides
Sulphates
Other ionic species
Condenser leakage
Cooling-water ingress
Why is cation conductivity important?
A small amount of contamination can become significant in high-pressure steam-water cycles. Cation conductivity therefore provides an important diagnostic parameter alongside direct conductivity.
A well-designed SWAS system should provide appropriate sample conditioning and cation-exchange arrangements for reliable measurement.
3. Degassed Cation Conductivity
Degassed cation conductivity is a further development of cation conductivity measurement.
After cation exchange, the sample is degassed to reduce the influence of dissolved gases such as carbon dioxide. Conductivity is then measured again.
This can help distinguish between conductivity contributions associated with dissolved gases and those associated with ionic contamination.
Comparison of:
Specific conductivity
Cation conductivity
Degassed cation conductivity
can provide useful information for cycle-chemistry diagnosis.
The interpretation should always consider the actual plant chemistry, sampling system and analyzer design.
4. pH
pH is a fundamental parameter for controlling the chemical environment of the steam-water cycle.
It provides an indication of whether the sample is acidic, neutral or alkaline.
Why monitor pH?
Correct pH control can help manage:
Corrosion
Chemical treatment
Feedwater chemistry
Condensate chemistry
Boiler-water chemistry
Material compatibility
pH monitoring is particularly important in feedwater and condensate systems.
SWAS requirements for pH measurement
Reliable pH measurement depends on:
Suitable sample pressure
Controlled sample temperature
Stable flow
Proper electrode condition
Correct calibration
Clean sample lines
pH electrodes require periodic inspection and replacement according to manufacturer recommendations and actual operating conditions.
5. Dissolved Oxygen
Dissolved oxygen (DO) is an important parameter in feedwater and condensate monitoring.
Excess dissolved oxygen can contribute to corrosion in parts of the steam-water cycle.
DO monitoring is therefore useful for checking the performance of:
Deaerators
Feedwater systems
Condensate systems
Chemical oxygen-scavenging programs where applicable
Modern SWAS systems can use low-level dissolved oxygen analyzers for continuous monitoring.
Because DO can be affected by air ingress and sample handling, the sample system must be designed carefully.
6. Silica
Silica is one of the most important parameters for high-pressure steam-cycle monitoring.
Silica can potentially carry over with steam and subsequently deposit on turbine components.
Why monitor silica?
Continuous silica monitoring can help detect:
Boiler-water contamination
Poor demineralization
Steam carryover
Water-treatment problems
Changes in steam purity
Silica monitoring is commonly required at selected locations in:
High-pressure boiler systems
Main steam
Condensate
Feedwater
HRSG systems
Silica analyzer principle
Many online silica analyzers use a chemical colorimetric method involving reagent addition and optical measurement.
The analyzer therefore requires careful management of:
Reagents
Tubing
Reaction chamber
Optical system
Calibration
Sample flow
7. Sodium
Sodium monitoring is another critical measurement in many high-purity steam-water cycles.
Even low concentrations of sodium can be significant in applications where steam purity is critical.
Sodium monitoring can help identify:
Condenser leakage
Cooling-water contamination
Make-up water contamination
Demineralizer problems
Steam contamination
Process ingress
Online sodium analyzers typically use an ion-selective measurement approach with appropriate sample conditioning.
Because sodium measurements can be sensitive to contamination, sample-system cleanliness is extremely important.
8. Phosphate
Phosphate monitoring is relevant in boiler-water chemistry programs where phosphate-based treatment is used.
The objective is to help maintain appropriate boiler-water chemistry and manage the treatment program.
Online phosphate analysis can be based on a chemical reaction followed by optical measurement.
The system may therefore include:
Reagent dosing
Reaction chamber
Optical detector
Calibration system
Sample conditioning
Drain arrangement
Phosphate monitoring requirements depend strongly on the plant's chemistry regime and treatment philosophy.
9. Chloride
Chloride is an important contaminant indicator in many steam-water cycles.
Elevated chloride levels can be associated with:
Cooling-water ingress
Condenser leakage
Make-up water contamination
Process contamination
Chloride monitoring may be performed online in specialized applications or through laboratory analysis and ion chromatography, depending on the plant's monitoring philosophy.
When chloride is included in an online SWAS system, the sampling and analyzer technology should be selected according to the required detection range and application.
10. Sulphate
Sulphate can also be used as an indicator of ionic contamination.
It may be relevant when investigating:
Cooling-water ingress
Condenser leakage
Water-treatment problems
Process contamination
Online measurement is application-dependent, while laboratory analysis may be used for detailed chemistry verification.
11. Temperature
Temperature is not normally considered a chemistry parameter, but it is one of the most important SWAS sample-system parameters.
Online analyzers have specified sample-temperature limits.
A sample cooler is therefore normally installed upstream of analyzers when the process sample temperature is too high.
Temperature monitoring helps:
Protect analyzers
Stabilize measurements
Prevent sample flashing
Improve measurement consistency
Detect cooling-system problems
A temperature sensor can also be connected to the PLC/HMI and DCS/SCADA system for alarm generation.
12. Sample Pressure
Sample pressure must be controlled before the sample enters many online analyzers.
High-pressure boiler and steam samples can require substantial pressure reduction.
A typical SWAS arrangement may include:
Process Sample → Isolation Valve → Pressure Reduction → Cooler → Flow Control → Analyzer
Pressure instrumentation can help identify:
Pressure regulator problems
Blockages
Valve problems
Abnormal process conditions
Sample-system restrictions
Pressure reduction and cooling should be engineered together because changing pressure can affect sample behavior, particularly for high-temperature samples.
13. Sample Flow
Stable sample flow is essential for reliable online analysis.
Too little flow can cause:
Slow analyzer response
Poor sample transport
Unstable readings
Excessive response time
Excessive flow can cause:
Unnecessary sample consumption
Pressure instability
Poor control of the sample system
Flowmeters and flow-control valves are therefore important components of a SWAS Panel.
There is no single universal SWAS flow rate. The required flow depends on the analyzer, sample-conditioning system, pressure, temperature, tubing arrangement and manufacturer requirements.
14. Sample Temperature and Flow as Diagnostic Parameters
A chemistry analyzer may indicate an abnormal value even when the actual plant chemistry is normal.
For this reason, operators should examine the sample-system conditions before concluding that an analyzer has failed.
For example:
High silica reading → Check sample flow → Check temperature → Check filtration → Check analyzer/reagents → Verify calibration
Similarly:
Unstable conductivity → Check flow → Check air bubbles → Check temperature compensation → Check sample cleanliness → Check sensor
This approach reduces unnecessary analyzer replacement.
15. Sample Conditioning Parameters
The quality of an SWAS measurement depends heavily on the condition of the sample reaching the analyzer.
Important conditioning variables include:
Sample pressure
Sample temperature
Sample flow
Filtration
Sample-line cleanliness
Pressure stability
Cooling-water availability
Air ingress
Drainage
A good SWAS design maintains these conditions within the requirements of each analyzer.
SWAS Parameters by Typical Sampling Location
Sampling LocationCommon ParametersCondensateConductivity, cation conductivity, DO, pH, sodiumFeedwaterpH, conductivity, cation conductivity, DO, sodium, silicaBoiler Drum WaterConductivity, pH, phosphate, silica, sodiumMain SteamConductivity, cation conductivity, sodium, silicaHRSG FeedwaterConductivity, cation conductivity, pH, DOHRSG SteamConductivity, cation conductivity, sodium, silicaMake-up WaterConductivity, pH, silica, sodiumCooling/Leakage InvestigationConductivity, cation conductivity, sodium, chloride where applicable
This is a general application guide, not a universal parameter specification. The final parameter list should be developed from the plant chemistry program, process design and equipment/OEM requirements.
Dedicated vs Multiplexed SWAS Monitoring
SWAS panels can be designed using dedicated analyzers or multiplexed arrangements.
Dedicated arrangement
Each analyzer continuously receives its designated sample.
Advantages:
Continuous measurement
Faster response
Less switching complexity
Easy interpretation
Multiplexed arrangement
One analyzer can sequentially monitor samples from multiple locations.
Advantages:
Reduced analyzer count
Lower initial equipment cost
Useful for selected applications
However, multiplexing introduces:
Switching time
Flushing requirements
Transport delay
Cross-contamination considerations
More complicated PLC logic
The choice should therefore be based on process criticality and required response time.
Online SWAS Panel and Plant Automation
A modern Online SWAS Panel can be integrated with:
PLC
HMI
DCS
SCADA
Historian
Plant alarm systems
Typical signals include:
Analyzer measurement
High/low alarm
Sample flow
Sample temperature
Sample pressure
Analyzer status
Calibration status
Communication status
Common fault
Reagent alarm
Communication may be implemented using suitable industrial interfaces such as analog signals, digital signals or industrial communication protocols depending on the project requirements.
SWAS Alarm Monitoring
A properly configured SWAS system should distinguish between:
Chemistry alarms
Examples:
High conductivity
High cation conductivity
High silica
High sodium
High dissolved oxygen
High/low pH
Sample-system alarms
Examples:
Low sample flow
High sample temperature
Low cooling-water flow
High sample pressure
Analyzer alarms
Examples:
Calibration failure
Sensor failure
Reagent low
Analyzer fault
Communication failure
This distinction makes troubleshooting much faster.
SWAS Panel Maintenance
Regular SWAS Panel Maintenance is essential because measurement accuracy depends on both the analyzer and sample-conditioning system.
Maintenance activities may include:
Daily/regular checks
Sample flow
Sample temperature
Pressure
Leakage
Analyzer status
Reagent level
Drain condition
Periodic maintenance
Filter cleaning/replacement
Sensor inspection
Calibration
Sample cooler inspection
Pressure regulator inspection
Flow-control inspection
Tubing inspection
Cation resin replacement where applicable
Reagent-system maintenance
Annual or scheduled maintenance
Complete panel inspection
Analyzer performance verification
Instrument calibration
Valve inspection
Electrical inspection
PLC/HMI verification
DCS/SCADA signal verification
Spare-parts review
Actual maintenance intervals should follow the analyzer manufacturer's recommendations and plant operating conditions.
Common Problems in SWAS Parameter Monitoring
Unstable readings
Possible causes include:
Variable sample flow
Air bubbles
Temperature fluctuations
Sensor fouling
Poor sample conditioning
Electrical noise
High conductivity
Possible causes include:
Genuine contamination
Condenser leakage
Chemical contamination
Dirty sample lines
Sensor contamination
High silica
Possible causes include:
Water-treatment problems
Contaminated sample
Steam carryover
Analyzer calibration/reagent problems
High sodium
Possible causes include:
Condenser leakage
Cooling-water ingress
Contaminated make-up water
Sample-system contamination
High dissolved oxygen
Possible causes include:
Air ingress
Deaerator performance issues
Sample-system leakage
Incorrect analyzer calibration
A useful troubleshooting sequence is:
Process → Sample Point → Pressure → Cooling → Flow → Filtration → Sensor → Analyzer → Signal → DCS/SCADA
How to Select the Right SWAS Panel
Before specifying a SWAS system, collect the following information:
Process information
Sample source
Pressure
Temperature
Flow
Sample chemistry
Sample-line distance
Analyzer requirements
Measurement parameter
Measuring range
Accuracy
Detection limit
Sample flow requirement
Sample temperature requirement
Calibration method
Panel requirements
Number of streams
Number of analyzers
Dedicated or multiplexed
Material of construction
Enclosure
Drainage
PLC/HMI
DCS/SCADA integration
Alarm requirements
Maintenance requirements
Sensor replacement
Reagent consumption
Calibration frequency
Filters
Cation resin
Recommended spares
Service support
Why Sample Conditioning Is as Important as the Analyzer
One of the most important principles in SWAS engineering is that an excellent analyzer cannot compensate for a poorly conditioned sample.
For example, a high-quality sodium analyzer may produce unreliable results if:
The sample line is contaminated
The flow is unstable
Air enters the system
The sample temperature is outside specification
Pressure reduction is incorrect
The sample is not representative
The SWAS Panel must therefore be engineered as one integrated system.
SWAS Panel India: Applications
In India, SWAS systems can be used in a wide range of industries, including:
Thermal power plants
Combined-cycle power plants
Captive power plants
Sugar mill cogeneration
Paper mills
Steel plants
Chemical plants
Refineries
Fertilizer plants
Pharmaceutical plants
Process industries
Industrial boiler systems
The required parameters vary according to the application and process chemistry.
Benefits of Continuous SWAS Monitoring
A properly engineered SWAS Panel can provide:
Continuous chemistry monitoring
Early contamination detection
Better boiler-water control
Improved steam purity monitoring
Protection against corrosion and deposits
Better turbine protection
Reduced dependence on intermittent sampling
Faster response to abnormal conditions
Historical data for trend analysis
Integration with plant automation
Improved maintenance planning
SWAS Panel Selection Checklist
Before purchasing a SWAS Panel, verify:
Sampling locations defined
Required parameters identified
Sample pressure documented
Sample temperature documented
Sample flow documented
Sample-line distance known
Pressure reduction designed
Sample cooler sized
Flow control provided
Filtration considered
Correct MOC selected
Analyzer ranges confirmed
Calibration requirements defined
Drainage provided
PLC/HMI requirements defined
DCS/SCADA integration defined
Alarm philosophy established
Maintenance requirements considered
Recommended spares identified
Frequently Asked Questions
What is the most important parameter in a SWAS Panel?
There is no single parameter that is most important for every plant. Conductivity, cation conductivity, pH, dissolved oxygen, silica and sodium are among the commonly monitored parameters, but the correct selection depends on the plant chemistry program and process design.
Why are silica and sodium monitored in steam systems?
Silica and sodium can be important indicators of steam purity and contamination. In high-pressure cycles, monitoring them can help detect conditions that may contribute to turbine deposits or other operational problems.
What is the difference between conductivity and cation conductivity?
Specific conductivity measures the conductivity of the sample directly. Cation conductivity measures conductivity after the sample has passed through a cation exchange medium, which can make certain anionic contaminants more apparent.
Why is dissolved oxygen monitored?
Dissolved oxygen can contribute to corrosion in steam-water systems. Continuous monitoring helps operators assess feedwater and condensate conditions and the performance of systems such as deaerators.
Does every SWAS Panel need a silica analyzer?
No. The parameter list depends on the plant, steam conditions, chemistry program and monitoring objectives. Silica is particularly important in many high-pressure steam-cycle applications.
How often should a SWAS Panel be maintained?
Maintenance frequency depends on analyzer technology, sample chemistry, operating conditions and manufacturer recommendations. Routine checks should include sample flow, temperature, pressure, leakage and analyzer status, with periodic calibration and component maintenance.
Can SWAS analyzers be connected to a DCS?
Yes. SWAS analyzers and their PLC/HMI systems can be integrated with plant DCS or SCADA systems using appropriate signal and communication interfaces.
What is the difference between online and grab sampling?
An online SWAS system continuously monitors a conditioned sample, while grab sampling collects a sample for laboratory analysis. Both can complement each other for process monitoring and verification.
Conclusion
A SWAS Panel is a critical part of steam and water chemistry management in modern power and industrial plants. Parameters such as conductivity, cation conductivity, pH, dissolved oxygen, silica, sodium and phosphate provide valuable information about cycle chemistry, contamination, corrosion risk and steam purity.
However, accurate measurement depends on much more than selecting the right analyzer. Sample extraction, pressure reduction, cooling, flow control, filtration, material selection, calibration, drainage and automation integration all contribute to reliable results.
For plants looking for a dependable Online SWAS Panel solution, the system should be engineered around the actual process conditions and analyzer requirements rather than using a one-size-fits-all design.
Prosoft Automation can support customers with SWAS panel selection, sample-conditioning design, online analyzer integration, PLC/DCS connectivity, commissioning and SWAS Panel Maintenance.
For more information, visit our SWAS Panels product section and download our product catalogue.
Request a quotation or discuss your SWAS application with Prosoft Automation.