co-author: Neil Hartman, CTO
Alicat mass flow instruments enable industrial oxygen production for precise control of glass shaping and melting
Many high technology applications ranging from chemically hardened glass production to fiber optic cable generation benefit from oxygen concentration technology. Pressure swing adsorption oxygen concentration systems allow for the replacement of more expensive and potentially dangerous oxygen cylinders or dewars. These systems work by passing air through an adsorbent bed at higher pressure, followed by desorption of nitrogen at lower pressure.1 Alicat’s Whisper series and bi-directional mass flow controllers are present in many of these systems. These innovative mass flow controllers are able to operate at the very low pressures these systems require (typically less than 10 psi). They also enable the fast switching between high and low pressures (control in less than 30ms).
Oxygen concentrators are often used in modern glass manufacturing to improve process efficiency. They provide the oxidizer needed to generate high temperature flames without the heat absorbing presence of nitrogen. The resulting higher flame temperatures also allow finer process control while lowering fuel costs. Many types of glass require melting or shaping at high temperatures (1400-1600 °C).2 Unlike water, glass has no melting or freezing point, merely a change from a stiff solid to a viscous mass. For conventional glass manufacturing, a melted gob is dropped into a blank mold to begin the process. In the blow and blow method, precise delivery of air (regulated by a flow controller) is critical to the proper shaping and transfer of the molten glass material.
Creation of optical cable fiber also has mass flow control requirements during the process of preform creation and polishing. Generating this type of glass requires specialized lathes, specific dopants and precisely controlled burners to create a preform with the necessary characteristics.3
Nextrom glass working lathe with high accuracy mass flow controller flame shown;
image courtesy of Rosendahl-Nextrom
Alicat takes a number of steps to uniquely enable these critical processes in optical cable fiber and preform manufacturing. Industrial scale oxygen concentration systems operate at low pressures (typically less than 10 psi), which in turn requires flow control with high accuracy at low pressures. Alicat’s Whisper series instruments have pressure drops as low as 0.06 psi while maintaining accuracy of 0.4% of reading or 0.2% of full scale. Additionally, Alicat’s bi-directional mass flow controllers maintain this high level of performance while simplifying flow lines by consolidating both high and low pressure flow paths through one controller. High flow meters and controllers are available from Alicat, for flow rates up to 5000 SLPM. These systems offer an unmatched steady state controllable range of 10,000:1, enabling consolidation of low, medium and high flow processes into one controller.
Unlike thermal mass flow controllers, Alicat’s differential pressure method allows for control of virtually any gas or mixture without a loss of accuracy. The Gas Select feature on Alicat meters and controllers includes mixtures preset for commonly used industrial gases (regardless of input type of source). Going one step further, Alicat’s Composer allows for accurate measurement and control of custom or novel gas mixtures. Composer functionality may be accessed directly from the front panel or remotely. With remote access, mixtures may be updated up to 12 times per second, in response to external analyzer results.
Finally, Alicat’s focus on customization allows for instruments designed specifically for your glass manufacturing processes. Mass flow controllers built with your choice of control (analog, digital or industrial protocols), innovative features like a built-in display, and choice of process connection typically ship within a few days. Coupled with customer-centric service we can ensure that the perfect controller, tailored to your needs will operate with peak efficiency. Speak with an engineer today to find out how Alicat can improve the efficiency of your glass process.
- “Pressure Swing Adsorption.” Wikipedia, Wikimedia Foundation, 20 Sept. 2019, https://en.wikipedia.org/wiki/Pressure_swing_adsorption.
- Glass Making, https://www.believersinglass.com/GlassMaking.php.
- Paschotta, Rüdiger. “Fiber Fabrication.” RP Photonics Encyclopedia – Fiber Fabrication, Preform, Pulling, MCVD, Chemical Vapor Deposition, Solution Doping, RP Photonics, 13 July 2019, https://www.rp-photonics.com/fiber_fabrication.html.