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Tin Bath Atmosphere Oxygen Sensor

Opening sidewallThe Read-Ox tin bath atmosphere oxygen sensor is engineered to measure the oxygen activity in the protective atmosphere of a tin bath. Exceptionally sensitive, it can detect even minute oxygen leaks, making it an indispensable tool for:

  • Identifying the need for sealing improvements
  • Adjusting venting intensity or hydrogen supply
  • Providing immediate feedback on the effectiveness of sealing actions

The atmosphere sensor enables real-time tracking of the log(pO2(bar)) and the log (pH2O/pH2) of the protective atmosphere. The pH2O/H2 buffer determines the reducing or oxidizing capacity the protective atmosphere, independent of the bath temperature.

installation atmosphere sensor 684x553

The atmosphere oxygen sensor is designed for seamless integration into existing tin bath setups. It can be installed in a side wall guide tube, similar to the placement of a standard tin bath thermocouple or tin melt oxygen sensor. The key distinction lies in the positioning of the measuring tip: while melt sensors are submerged in the tin, the atmosphere sensor’s tip is located above the tin melt, within the protective atmosphere.  The sensor is equipped with a large aluminum terminal head, offering ample space for easy and secure connection of signal cables. These include the thermocouple millivolt signal and the oxygen cell millivolt signal or EMF. Both signals are routed to the IOSI signal converter, ensuring accurate and reliable data processing.

 

 

By simultaneously measuring the oxygen activity in the tin melt and in the protective atmosphere within a specific bay, operators gain valuable insight into the driving force for tin melt deoxidation. This dual monitoring capability allows for:

  • Precise control of deoxidation dynamics
  • Enhanced oxygen removal efficiency
  • Optimized atmosphere management across different bath sections

 

Two types of tin bath atmosphere oxygen sensors are available to suit varying temperature zones within the tin bath:

  • The standard sensor is designed for use in the mid-bath and hot-end sections, with an application range of 650 to 1000°C. It offers reliable performance under medium and high-temperature conditions typical of these section.
  • The cold-end atmosphere sensor features a highly sensitive oxygen cell optimized for lower temperature environments, with an application range of 550 to 650°C. This variant ensures accurate oxygen activity measurement in cooler sections of the bath.

Driving force for tin melt deoxidation

Under standard production conditions, the oxygen activity of the protective atmosphere is maintained lower than that of the tin melt to promote effective oxygen removal. This differential ensures that the oxygen content in the tin melt remains sufficiently low to support defect-free glass production. Since the majority of the tin melt surface is covered by the glass ribbon, oxygen tends to become trapped beneath it. The deoxidation process is inherently slow and can only occur through the narrow open spaces near the side walls of the bath.

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Figure Oxygen Cycle

Control scheme

Therefore, it is essential to monitor both the oxygen activity in the tin melt and in the protective atmosphere at multiple points along the bath to maintain a sufficient driving force for deoxidation throughout its entire length.

A comprehensive study on oxygen behavior in the tin bath — including the use of paired tin melt and atmosphere oxygen sensors from hot end to cold end — was conducted by the Asahi Glass Production Technology Center. The findings were published in Glass Technology: European Journal of Glass Science and Technology A, December 2012, Volume 53 (6), pp. 261–272

Signal converter

Read-Ox offers a DIN rail-mountable oxygen sensor interface (IOSI-02), purpose-built for seamless integration with Read-Ox oxygen sensors. The tin bath atmosphere oxygen sensor outputs two millivolt signals: one from the oxygen cell and one from a built-in type K thermocouple. These signals are processed by the IOSI-02 and converted into three analog 4–20 mA outputs, enabling straightforward integration into industrial control systems. The default output configuration is as follows:

  • I-out1: Temperature of the protective atmosphere: 4..20 mA = 0..1200 (ºC)
  • I-out2: Log (pO2) of the protective atmosphere: 4..20 mA = -40..-10 (-)
  • I-out3: Log (pH2O/pH2) of the protective atmosphere: 4..20 mA = -4..2 (-)

 

The output calculations and signal ranges of the IOSI-02 can also be customized via its USB port using the dedicated IOSI02config PC application. This software allows end users to tailor the IOSI-02 interface to their specific operational requirements, ensuring optimal integration and performance. For a comprehensive overview of the IOSI-02 oxygen sensor interface, including technical specifications and configuration options, please click here...

 

 

Read-Ox provides a custom-engineered Teflon extension cable, rated for continuous operation at temperatures up to 250 °C. The cable features four conductors, each color-coded to match the contact blocks within the sensor head, ensuring straightforward and reliable connection to the IOSI-02 interface. This design simplifies installation and minimizes the risk of wiring errors in high-temperature environments.