Introduction

Selecting the correct SWAS Panel (Steam and Water Analysis System) is an important decision for power plants, process industries and other facilities where continuous monitoring of steam and water chemistry is required.

A SWAS Panel is not simply a cabinet containing online analyzers. It is a complete sample-conditioning and analytical system designed to extract representative samples, reduce pressure, control temperature, regulate flow and deliver suitable samples to online analyzers.

Incorrect sizing can result in:

• Excessive sample temperature

• Insufficient cooling

• Unstable sample flow

• Excessive pressure

• Long sample transport time

• Analyzer measurement errors

• Frequent maintenance

• Higher operating costs

• Poor system reliability

Therefore, SWAS Panel sizing and selection should be based on actual process conditions, sample characteristics, analyzer requirements and plant operating philosophy.

This guide explains the major factors to consider when selecting an Online SWAS Panel.

What Is a SWAS Panel?

A SWAS Panel is a sample extraction, conditioning and analysis system used for continuous monitoring of steam and water chemistry.

Depending on the application, a system can include analyzers for:

• Silica

• Sodium

• pH

• Conductivity

• Cation conductivity

• Dissolved oxygen

• Phosphate

• Chloride

• Other water chemistry parameters

A typical sample path may be:

Process Sample Point → Isolation → Pressure Reduction → Cooling → Filtration → Flow Control → Analyzer → Drain/Return

The exact arrangement depends on the process and analyzer requirements.

Why Correct SWAS Panel Sizing Is Important

A SWAS system must be sized for both normal and abnormal operating conditions.

Poor sizing can cause:

1. Insufficient Cooling

The analyzer may receive a sample above its permitted temperature.

2. Excessive Flow

High flow can waste sample water and make measurement unstable.

3. Low Flow

Low flow can increase transport time and cause unstable analyzer readings.

4. Excessive Pressure

High pressure can damage downstream components.

5. Inadequate Pressure Control

Pressure fluctuations can result in unstable flow and temperature.

6. Long Response Time

An excessively long sample line can delay detection of chemistry changes.

7. Higher Maintenance

Poorly sized components can increase filter blockage, valve wear and cooler problems.

Major Factors in SWAS Panel Sizing

The following parameters should be established before selecting the panel.

1. Number of Sample Streams

Determine how many process sample points must be monitored.

Possible sample streams include:

• Main steam

• Reheat steam

• Feedwater

• Condensate

• Boiler water

• Deaerator outlet

• Makeup water

• Cooling water

• Other critical streams

A single-stream system can be relatively simple, while a multi-stream SWAS system may require a much larger conditioning and analyzer arrangement.

2. Number of Analyzers

Determine which parameters need continuous measurement.

For example, a power plant may require:

• pH

• Conductivity

• Cation conductivity

• Dissolved oxygen

• Silica

• Sodium

Another plant may require only conductivity and pH.

The number of analyzers affects:

• Panel size

• Sample distribution

• Flow requirements

• Drain capacity

• Electrical requirements

• PLC I/O

• Maintenance access

3. Sample Temperature

Sample temperature is one of the most important sizing parameters.

The designer should know:

• Normal sample temperature

• Maximum sample temperature

• Minimum sample temperature

• Temperature at the sample point

• Required analyzer inlet temperature

The sample cooler must then be sized to achieve the required outlet temperature under the worst expected operating condition.

There is no universal SWAS sample temperature that applies to every analyzer.

The final value should be based on the analyzer manufacturer's specifications and the complete sample-conditioning design.

4. Sample Pressure

The sample pressure determines the requirements for:

• Sample tubing

• Valves

• Pressure regulators

• Restrictors

• Sample coolers

• Fittings

The design should consider:

• Normal pressure

• Maximum pressure

• Minimum pressure

• Pressure fluctuations

• Startup conditions

• Shutdown conditions

High-pressure sample points may require staged pressure reduction rather than a single large pressure drop.

5. Sample Flow Rate

Flow is critical for both sample transport and analyzer operation.

The required flow depends on:

• Analyzer requirements

• Sample-line length

• Tubing diameter

• Pressure

• Temperature

• Sample cooler

• Filters

• Flow-control devices

There is no universal flow rate for every SWAS Panel.

The required flow should be determined from the analyzer manufacturer and complete sample-system design.

A useful relationship is:

Transport Time = Sample-Line Volume ÷ Sample Flow Rate

A lower flow rate can increase sample transport time.

6. Sample-Line Length

The distance between the process sample point and SWAS Panel can significantly influence system design.

Long sample lines can result in:

• Increased transport time

• Heat loss

• Pressure drop

• Higher sample volume

• Greater risk of contamination

• More maintenance points

Where possible, the SWAS Panel should be located reasonably close to the sample source while maintaining safe and accessible installation conditions.

7. Sample Chemistry

The chemistry of the sample determines:

• Material of construction

• Filter selection

• Analyzer selection

• Sensor compatibility

• Cleaning requirements

• Chemical conditioning

Important parameters may include:

• pH

• Conductivity

• Sodium

• Silica

• Chloride

• Sulphate

• Dissolved oxygen

• Phosphate

• Suspended solids

• Chemical treatment products

The wetted materials should be compatible with the actual sample.

How to Size the Sample Cooler

The sample cooler must remove enough heat to bring the sample into an appropriate temperature range.

A simplified heat-balance relationship is:

Q = m × Cp × ΔT

Where:

• Q = heat transfer

• m = mass flow rate

• Cp = specific heat

• ΔT = temperature difference

The cooler design should consider both:

Sample Side

• Inlet temperature

• Outlet temperature

• Sample flow

• Pressure

Cooling Side

• Cooling-water temperature

• Cooling-water flow

• Cooling-water pressure

• Seasonal variation

For Indian installations, summer cooling-water conditions should be considered where they can materially affect cooler performance.

Final cooler sizing should be confirmed using actual process data and the cooler manufacturer's calculations.

How to Size Sample Tubing

Tubing should be selected based on:

• Pressure rating

• Temperature rating

• Flow

• Material compatibility

• Sample-line length

• Pressure drop

• Installation environment

The tubing should not be selected solely on the basis of nominal diameter.

An excessively small tube can cause:

• High pressure drop

• Low flow

• Longer response time

• Greater susceptibility to blockage

An unnecessarily large tube can increase:

• Sample volume

• Transport time

• Water consumption

The objective is to achieve a stable and representative sample flow.

How to Select Pressure Regulators

Pressure-control equipment must be selected according to:

• Inlet pressure

• Outlet pressure

• Flow

• Temperature

• Sample chemistry

• Valve material

• Pressure rating

For high-pressure applications, a staged pressure-reduction arrangement may be more appropriate.

The design should also consider flashing and two-phase flow where applicable.

Flow Control and Flowmeter Selection

A flowmeter should provide a useful measurement range around the actual operating flow.

Possible technologies include:

• Rotameters

• Variable-area flowmeters

• Electronic flowmeters

• Flow transmitters

The flow-control valve should provide stable adjustment without becoming excessively sensitive.

For critical systems, flow measurement can be connected to the PLC and used for alarm generation.

Filter Sizing

Filters are often incorporated to protect downstream analyzers.

Selection should consider:

• Particle loading

• Filtration rating

• Sample flow

• Pressure drop

• Temperature

• Cleaning requirements

• Replacement availability

An excessively fine filter can create unnecessary pressure drop and frequent blockage.

The filter should therefore be selected based on the actual analyzer requirements.

Sizing a Multi-Analyzer SWAS Panel

When several analyzers are connected to one sample stream, the sample system must provide sufficient flow to all branches.

For example:

Conditioned Sample → Distribution Header →

• Silica Analyzer

• Sodium Analyzer

• Conductivity Analyzer

• pH Analyzer

• DO Analyzer

Each branch may require individual flow control.

The design should ensure that one analyzer branch does not unintentionally starve another.

Multi-Stream SWAS Panel Selection

For multiple process streams, the designer must decide between:

Dedicated Analyzer per Stream

Each stream has its own analyzer or analyzer set.

Advantages:

• Continuous measurement

• Fast response

• No stream-switching delay

• Simple interpretation

Disadvantages:

• Higher capital cost

• More analyzers

• Larger panel

• Higher maintenance requirements

Multiplexed Analyzer System

One analyzer may sequentially monitor several streams.

Advantages:

• Lower analyzer cost

• Reduced instrumentation

• Smaller analyzer inventory

Disadvantages:

• Sequential rather than simultaneous measurement

• Stream-switching time

• Potential cross-contamination

• More complex valve control

• Greater dependence on sequencing logic

The correct approach depends on the criticality of each measurement.

How to Select Analyzers for a SWAS Panel

Analyzer selection should begin with the measurement objective.

Silica Analyzer

Used for monitoring silica contamination and steam-cycle chemistry.

Important selection factors include:

• Measuring range

• Detection capability

• Response time

• Sample requirements

• Reagent requirements

• Calibration method

• Maintenance requirements

Sodium Analyzer

Used for detecting very low-level sodium contamination.

Consider:

• Required detection range

• Sample conditioning

• Calibration

• Reagent/conditioning requirements

• Material compatibility

Conductivity Analyzer

Used for general water chemistry monitoring.

Consider:

• Measuring range

• Cell constant

• Temperature compensation

• Installation arrangement

Cation Conductivity

Useful for detecting ionic contamination in high-purity water systems.

Consider:

• Ion-exchange column

• Sample flow

• Resin replacement

• Temperature compensation

Dissolved Oxygen Analyzer

Used to monitor oxygen levels in feedwater and other critical streams.

Consider:

• Measuring range

• Sample integrity

• Sensor technology

• Calibration

• Air ingress prevention

pH Analyzer

Selection should consider:

• Measurement range

• Temperature

• Sensor type

• Reference system

• Calibration

• Sample flow

Selecting the SWAS Panel Enclosure

The enclosure or panel structure should be selected based on the installation environment.

Consider:

• Indoor or outdoor installation

• Ambient temperature

• Humidity

• Dust

• Corrosive atmosphere

• IP rating

• Access requirements

• Maintenance space

Common construction options include:

• Stainless steel

• Painted carbon steel

• Powder-coated steel

For outdoor installations, environmental protection becomes particularly important.

Panel Size and Layout

Panel dimensions depend on:

• Number of sample streams

• Number of analyzers

• Number of valves

• Sample coolers

• Flowmeters

• Filters

• PLC/HMI

• Electrical components

• Reagent systems

• Maintenance access

A panel should not be made so compact that technicians cannot safely access components.

Adequate space should be provided for:

• Valve operation

• Filter replacement

• Sensor removal

• Calibration

• Tubing maintenance

• Analyzer servicing

Sample Conditioning Panel vs Analyzer Panel

In some projects, sample conditioning and analysis are integrated into one panel.

In larger installations, they may be divided into:

Sample Conditioning Panel

Contains:

• Pressure reduction

• Cooling

• Filtration

• Flow control

• Sample distribution

Analyzer Panel

Contains:

• Online analyzers

• Sample cells

• PLC/HMI

• Electrical and communication equipment

This arrangement can improve accessibility and maintenance.

Electrical and Control Sizing

A modern Online SWAS Panel may include PLC-based monitoring and control.

The electrical design should consider:

• Number of analyzers

• Number of analog inputs

• Digital inputs

• Digital outputs

• Communication interfaces

• Solenoid valves

• Pumps

• Heaters where applicable

• HMI

• Power consumption

• UPS requirements where applicable

The I/O list should be prepared before finalizing the PLC.

DCS/SCADA Integration

The selected SWAS system should be compatible with the plant's control architecture.

Typical signals may include:

Process Values

• Silica

• Sodium

• Conductivity

• pH

• DO

• Temperature

• Pressure

• Flow

Status

• Analyzer healthy

• Analyzer fault

• Calibration status

• Sample flow status

• High temperature

• Low flow

• System fault

Communication can be implemented through project-approved interfaces such as:

• 4–20 mA

• Modbus RTU

• Modbus TCP

• Ethernet

• Profibus

• Profinet

• OPC

SWAS Panel Selection and Material of Construction

Material selection should be based on actual process conditions.

Possible materials include:

• SS 316L

• SS 304/304L

• PTFE

• PFA

• PVDF

• Polypropylene

• Other application-specific materials

Wetted components should be selected based on:

• Temperature

• Pressure

• Sample chemistry

• Corrosion potential

• Contamination risk

This is particularly important for low-level sodium, silica and dissolved oxygen measurement.

SWAS Panel Maintenance Requirements

Selection should not stop at initial purchase price.

A good SWAS Panel Maintenance strategy should consider:

• Filter replacement

• Valve servicing

• Cooler cleaning

• Sensor replacement

• Calibration

• Tubing inspection

• Leak inspection

• Reagent replacement

• Analyzer servicing

• PLC/HMI checks

• DCS communication checks

The system should be designed so routine maintenance can be performed without unnecessarily shutting down the entire monitoring system.

Spare Parts Planning

A professionally selected SWAS system should have an appropriate spare-parts strategy.

Recommended critical spares may include:

• Analyzer sensors

• Electrodes

• Filters

• Tubing

• Fittings

• Seals

• Valve repair kits

• Flowmeters

• Reagent pumps

• Fuses

• Power supplies

• Critical analyzer consumables

The exact spare list should be based on the selected equipment and manufacturer's recommendations.

SWAS Panel India: Selection Considerations

For SWAS Panel India projects, local operating conditions should be considered during selection.

These may include:

• High ambient temperature

• Seasonal variation

• Cooling-water temperature

• Dust

• Humidity

• Outdoor installation

• Availability of cooling water

• Availability of instrument air

• Local service support

• Spare-part availability

A system selected only from catalogue specifications without reviewing actual site conditions may not perform optimally after installation.

SWAS Panel Sizing – Basic Engineering Data Sheet

Before requesting quotations, it is useful to prepare a site data sheet.

ParameterRequired InformationNumber of sample streamsNumberSample sourceMain steam/feedwater/etc.Sample temperatureNormal/maximumSample pressureNormal/maximumSample flowAvailable flowSample-line lengthMetresCooling-water temperatureNormal/maximumCooling-water pressureNormal/maximumRequired analyzersParameter listRequired measuring rangesAnalyzer-wiseInstallationIndoor/outdoorAmbient temperatureRangePower supplyVoltage/frequencyInstrument airAvailable/not availableDCS interfaceRequired protocolDrain arrangementAvailable/requiredMaterial standardProject requirementEnclosure requirementIP ratingSpecial requirementsAs applicable

This information allows a supplier to develop a more accurate technical proposal.

SWAS Panel Selection – Step-by-Step Process

Step 1: Identify the Application

Determine why the SWAS system is required.

Examples:

• Boiler chemistry control

• Steam purity monitoring

• Condensate monitoring

• Feedwater chemistry

• Corrosion control

• Contamination detection

Step 2: Identify Sample Points

Prepare a complete sample-point list.

Step 3: Establish Process Conditions

Collect:

• Pressure

• Temperature

• Flow

• Chemistry

Step 4: Define Required Parameters

Determine which analyzers are required.

Step 5: Define Analyzer Ranges

Avoid selecting analyzers solely on the basis of the lowest possible range.

The normal operating point should also be considered.

Step 6: Design Sample Conditioning

Select:

• Pressure control

• Cooling

• Filtration

• Flow control

• Distribution

Step 7: Select MOC

Evaluate wetted and non-wetted materials.

Step 8: Define Control Architecture

Determine:

• PLC

• HMI

• Local alarms

• DCS/SCADA interface

Step 9: Define Maintenance Philosophy

Ensure sufficient access and isolation points.

Step 10: Review Total Cost of Ownership

Evaluate:

• Initial cost

• Consumables

• Calibration

• Spares

• Service

• Energy/utilities

• Maintenance

Common SWAS Panel Selection Mistakes

Choosing Based Only on Price

The lowest purchase price may result in higher lifecycle costs.

Ignoring Sample Conditions

Analyzer specifications alone are not enough.

Using Generic Flow Rates

Flow must be based on actual analyzer and sample-system requirements.

Under-Sizing the Cooler

This can cause excessive analyzer inlet temperature.

Ignoring Sample Transport Time

Long sample lines can delay detection of chemistry changes.

Insufficient Maintenance Space

Compact panels may become difficult to service.

Not Considering Spare Availability

Long lead times for sensors or valves can increase downtime.

Ignoring DCS Integration

The analyzer may work locally but fail to provide useful plant-wide information.

Using Incompatible Materials

This can cause corrosion or sample contamination.

SWAS Panel Selection for Different Applications

Thermal Power Plants

Typical parameters may include:

• Conductivity

• Cation conductivity

• pH

• Silica

• Sodium

• Dissolved oxygen

Combined-Cycle Power Plants

Monitoring requirements can include:

• Feedwater chemistry

• Condensate chemistry

• Steam chemistry

• Cooling-water-related parameters

Boiler Plants

Typical monitoring may include:

• pH

• Conductivity

• Silica

• Phosphate

• Dissolved oxygen

Water Treatment Plants

Depending on the process, systems may include:

• Conductivity

• pH

• TDS-related measurements

• Specific ions

• Other online water-quality parameters

The final analyzer package should always be determined from the plant chemistry program.

SWAS Panel Sizing Checklist

Before approving the design, verify:

• Sample streams identified

• Sample points identified

• Sample pressure known

• Maximum pressure known

• Sample temperature known

• Maximum temperature known

• Sample flow known

• Sample-line length known

• Sample chemistry reviewed

• Required analyzers identified

• Measuring ranges defined

• Cooler sized

• Pressure regulators selected

• Flowmeters selected

• Filters selected

• Tubing selected

• Wetted materials verified

• Panel/enclosure selected

• Maintenance access checked

• Drainage confirmed

• Cooling-water requirements confirmed

• Electrical requirements confirmed

• PLC I/O identified

• DCS/SCADA interface defined

• Calibration arrangement defined

• Spare-parts list prepared

• Documentation requirements defined

How Prosoft Automation Can Help

Selecting and sizing a SWAS system requires more than simply choosing an analyzer from a catalogue.

Prosoft Automation can assist with application-based evaluation covering:

• Sample-point requirements

• Sample pressure and temperature

• Sample conditioning

• Cooling requirements

• Flow control

• Online analyzer selection

• Material of construction

• Multi-stream configurations

• PLC/HMI integration

• DCS/SCADA communication

• Calibration arrangements

• Maintenance access

• Spare-parts planning

The final configuration can be developed according to the plant's actual process conditions and monitoring requirements.

Frequently Asked Questions

What information is required to size a SWAS Panel?

The most important information includes the number of sample streams, sample pressure, temperature, flow, sample-line length, chemistry, required analyzers, measuring ranges, cooling-water conditions and site installation requirements.

Is there a standard size for a SWAS Panel?

No. Panel dimensions depend on the number of sample streams, analyzers, conditioning components, control equipment and maintenance-access requirements.

How is SWAS Panel cooling capacity determined?

Cooling capacity depends on sample temperature, sample flow, required outlet temperature and cooling-water conditions. A heat-balance calculation and manufacturer sizing should be used.

What determines SWAS sample flow?

Sample flow depends on the analyzer requirements, sample-line dimensions, pressure, temperature, cooling system, filters and flow-control arrangement.

How many analyzers can be installed in one SWAS Panel?

There is no universal limit. The practical number depends on panel size, sample streams, sample-conditioning requirements, analyzer dimensions, utilities and maintenance access.

Should each sample stream have a separate analyzer?

Not necessarily. Some applications use dedicated analyzers, while others use multiplexed systems. The decision depends on measurement criticality, response time and project economics.

What is the difference between SWAS sizing and analyzer selection?

Analyzer selection determines what needs to be measured and the analyzer's operating requirements. SWAS sizing determines how the sample-conditioning system can reliably deliver a suitable sample to those analyzers.

Why is maintenance important during SWAS selection?

A system that is difficult to access or requires frequent specialist intervention can have a higher lifecycle cost. Maintenance access, spares, calibration and service requirements should therefore be considered before purchase.

Is SWAS Panel selection different in India?

The basic engineering principles are the same, but site-specific conditions such as ambient temperature, cooling-water temperature, dust, humidity, service availability and spare-part logistics should be considered for SWAS Panel India projects.

Conclusion

Correct SWAS Panel sizing and selection is essential for obtaining reliable steam and water chemistry measurements.

A properly selected system should begin with the process conditions and work through the complete sample path:

Sample Point → Pressure Reduction → Cooling → Filtration → Flow Control → Sample Distribution → Analyzer → Drain/Return

The number of sample streams, analyzer requirements, sample pressure, temperature, flow, chemistry, sample transport distance, material compatibility, cooling-water conditions and plant control-system requirements should all be evaluated before finalizing the design.

For an Online SWAS Panel, the objective should not simply be to obtain the lowest initial purchase price. The system should provide stable sample conditions, reliable measurements, safe operation, convenient maintenance and acceptable lifecycle costs.

For SWAS Panel India applications, site-specific environmental and utility conditions should also be incorporated into the design.

A properly engineered system can improve chemistry monitoring, reduce maintenance problems and provide operators with timely information needed to protect boilers, turbines and the overall steam-water cycle.

Prosoft Automation – SWAS Solutions

Prosoft Automation provides application-oriented SWAS and online water chemistry monitoring solutions for power plants and industrial applications.

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