Vaisala Polaris™ PR53SD Process Refractometer

Pulp industry process optimization, black liquor, green liquor, brown stock washing, and other liquid concentrations in fiber and chemical recovery lines 

The Vaisala Polaris PR53SD Process Refractometer model is for the toughest process conditions in the pulp industry, measuring black liquor, green liquor, brown stock washing and other liquid concentrations in the fiber and chemical recovery lines. 

Stable and reliable measurement is in our core, and the process refractometer is retractable for service without process shutdown, minimizing downtime in the measurement. Therefore, the PR53SD instrument is for the critical and safety measurements in pulp mills.  

The modern, brand-new design on the SAFE-DRIVE retractor system enhances safety by integrating the process refractometer and the retractor as one, simple system. This prevents inadvertent errors in use and ensures that the isolation valve is closed before the instrument is removed. The system is easy to operate, consisting of only a few steps to insert or remove the process refractometer from pressurized process line with full operation ongoing. 

Unique in the world, Vaisala offers a retractable refractometer with a wash nozzle for green liquor. Same, accurate measurements inline also with high solids concentrations up to 85 % in black liquor. 

Advanced optical image analysis and diagnostics for prism wash

Advanced optical image analysis and diagnostics help users to quickly analyze wash performance. 

Get full data from the latest wash, along with comparable visual information, and adjust wash parameters accordingly. Fast and easy. 

Key benefits

Critical and safety measurements in pulp mills

The process refractometer design is in compliance with the BLRBAC Recommended Good Practice Safe Firing of Black Liquor in Black Liquor Recovery Boilers. 

Measure in all process conditions

Product measures reliably in various process conditions, including high heat, sticky process, rapidly changing process condition and with particles or fibers in the process.

New, safe and simple design for the SAFE-DRIVE retractor

Insert and remove from pressurized process line. The SAFE-DRIVE retractor design prevents inadvertent errors in use. 

Total dissolved solids, the only true measurement of organics and inorganics

Weak liquor and black liquor are a mixture of cooking chemicals and dissolved organic material. The RI measurement responds to all dissolved solids. Bubbles, foam, particles, suspended solids or fibers do not affect measurement. 

Plug & play to Indigo520

Expand features, including wash control, data storage, graphical interface, analog and digital interface by connecting to Vaisala Indigo520 transmitter. Convenient service with the Plug & play feature with minimized downtime should service be needed.

Customizable product with our Engineer to Order service

Big pipes, small pipes, spool pieces, washing system, spare parts, specific drawings? When one size does not fit all, Vaisala can tailor products to fit your specific needs.

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Pulp, paper and wood

Vaisala's inline dry solids content, and humidity and temperature measurement solutions help paper chemical companies, kraft chemical and semi-mechanical pulp mills, and paper and wood mills achieve high efficiency and essential properties in pulp, paper, paperboard, wood and timber products. Explore our full offering and applications.


Product resources


Brown stock washing optimization

Did you know that Total Dissolved Solids (TDS) is the only measurement that accounts for both inorganics and organics? Learn about this measurement parameter for Brown Stock Washing.



Measuring Real-Time TTA/Density of Green Liquor in Pulp Mill Causticizing with Process Refractometers

In this webinar you will learn about different methods to measure and control Green Liquor TTA/density in the causticizing process. 

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Importance of brown stock washing and digester dissolved solids optimization for pulp mill efficiency

In an optimal case brown stock washing removes as much dissolved solids as possible while using the lowest amount of wash liquor or water.

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Advantages of real-time dissolved solids content (TDS) measurement in fiber suspensions + implementation in individual BSW process steps and upper level process control

Experts will present advantages of real time dissolved solids measurement on specific focus points of the fiberline, as well as an optimization practice of the entire brown stock washing based on these unique measurement devices. 

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Real-life use cases on control practices and impacts before and after TDS technology implementation in brown stock washing

The focus is on how mills have identified bottlenecks and improved economics using Optimized Dilution Factor (DF) functionality. 

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How refractometer prism washing in challenging applications can create a competitive advantage

How do I know if my application needs a prism washing system? In some demanding applications, a prism washing system is necessary, which we’ll look at more closely in this article. 

Learn more

Divert Control System

Vaisala K-PATENTS® Digital Divert Control System DD-23

for black liquor and green liquor dry solids content and density measurements and recovery boiler safety in the kraft chemical (sulfate) and chemi-mechanical pulp production processes. 

Product page

Support material of the previous generations

Manuals, safety instructions, and videos for PR-23-SD SAFE-DRIVE Generation 1, Generation 2, and Generation 2.1.

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Interested to receive more information on a specific application or product? Drop us a line, and we'll get back to you!

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