Valmet Acoustic Pyrometer

Valmet Acoustic Pyrometer flue gas temperature measurement system

Valmet Acoustic Pyrometer is a non-contact measurement device that obtains highly accurate instantaneous gas temperature data in any area of the boiler.

Valmet Acoustic Pyrometer system utilizes the principle that the velocity of sound through a medium is related to the temperature of the medium. Instantaneous temperature data is spatially averaged and can provide zonal temperature maps.

The system generates a sound wave with a very sharp rise time and measures the time it takes to traverse the chamber. When the distance between the sound source and the receiver is known, the average temperature between the two points can be determined. The system can distinguish between equipment sounds, such as sootblowers, which are of limited duration, and persistent sounds, such as tube leaks.

Acoustic Signal Generators can be mounted horizontally or vertically to accommodate space restrictions.

Acoustic Signal Receivers detect sounds in the boiler via a tube through the wall and are housed in pressure-sealed NEMA 4 enclosures. Boiler tube bends are not required to mount the Acoustic Signal Receivers.

Key applications for the Valmet Acoustic Pyrometer include furnace flue gas temperature and temperature distribution measurement.


  • Significantly reduce slagging by maintaining optimal furnace flue gas temperatures
  • Avoid tube damage and leaks by avoiding hot spots and thermal shock
  • Improve heat transfer rate by balancing combustion
  • Reduce emissions by managing critical temperature profiles

Acoustic Pyrometer – Planar temperature map from any area of your boiler

Significant technical advantages


Valmet Acoustic Pyrometer system provides instantaneous, spatially averaged temperatures with less than 1% error. In contrast, thermocouples provide only point measurements and are subject to radiant heat effects, whereas IR pyrometers are spatially and temporally limited and must also compensate for emissivity errors.


The system is designed for superior reliability in hot, dirty environments. Ports are cleared by periodic air blasts and components are not sensitive to dust or dirt. This contrasts with optical pyrometers, which require optical train maintenance and port cleaning. Routine seal maintenance for the Valmet Acoustic Pyrometer system is required every 6 to 12 months, and field service is available on a contract or individual visit basis.

Configuration Flexibility

Valmet Acoustic Pyrometer system can be configured to meet your monitoring needs. Acoustic Signal Generators or Acoustic Signal Receivers can be added as desired.

Related articles

Valmet and Toshniwal Industries sign a cooperation agreement for Valmet Acoustic Pyrometers in India

Valmet and Toshniwal Industries sign a cooperation agreement for Valmet Acoustic Pyrometers in India

Valmet has signed a cooperation agreement for Valmet Acoustic Pyrometers with Toshniwal Industries, an Indian manufacturer of temperature instruments.

Success with the Valmet Acoustic Pyrometer at the Xinyuan Power Plant

Success with the Valmet Acoustic Pyrometer at the Xinyuan Power Plant

Xinyuan power plant in China measures boiler furnace temperatures continuously with a Valmet's acoustic temperature measurement system.




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