Development & Manufacturing of a Boric Acid Disc for a High Voltage Electrical Application

Development & Manufacturing of a Boric Acid Disc for a High Voltage Electrical Application

At TAB-PRO LLC we specialize in the manufacture of tablets for a variety of applications and industries. The project highlighted here is a 95% boric acid disc, which is designed for use as a spark arrestor in 10 kilovolt electrical switches. This was an upgrade to the customer's current switch; the housing was being damaged/melted by the arc that was created when the switch was thrown. The boric acid disc was added to the switch to mitigate this problem. The tablet is designed to absorb the arc, protecting the housing, and when the disc was burned out it was easy to replace because of the drilled out offset depression.

We utilized several processes to manufacture the tablet, including wet granulation, drying, milling, tableting, heating, and precision drilling. This project required the use of various manufacturing systems including our 5 gallon pony mixer; Colton wet granulator, Stokes 31A oven, Fitzmill D6, Stokes R-Press, and our Gehnrich oven. Composed of boric acid and friendly plastic, manufacturing required the plastic to be dispersed with solvent on the boric acid granules; After heating, the tablet fuses as a mesh matrix which holds the disc together. The completed dimensions of the spark arrestor tablet were 1.94" in diameter with a .44" drilled offset depression and height of .115". The tablet weighed 6.8 grams and was manufactured with a tolerance of ±.005". All customer specifications were adhered to and this project was subject to a stringent quality control program measuring height, weight, and hardness every minute at start-up and every 5 minutes thereafter. This project represents a production run of 10,000 tablets, which was completed in just 2 days.

For more information on this project, or the processes involved with manufacturing it, see the table below, or contact us directly.

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Boric Acid Disc Project Specifications

Product Description A 95% Boric Acid Disc used as a Spark Arrestor in 10 Kilovolt Electrical Switches. The arc created when the switch was thrown would damage/melt the housing of the switch. The Boric Acid disc was added to the switch and would absorb the arc, protecting the housing. When the boric acid disc was burned out it was easy to replace with another because of the drilled out offset depression
Capabilities Applied/Processes Primarily:
Wet Granulation, Drying, Milling, Tableting, Heating, and Drilling.
Equipment Used to Manufacture Part 5 Gallon Pony Mixer, Colton Wet Granulator, Stokes 31A Oven, Fitzmill D6, Stokes R-Press, Gehnrich Oven.
Overall Part Dimensions Diameter: 1.94" diameter w/0.44" drilled offset depression.
Weight: 6.8 gram
Height: 0.115"
Tightest Tolerances +-0.005"
Material Used Boric Acid, Friendly Plastic
In process testing/inspection performed Press operator checks height, weight, and hardness every minute at start-up and every 5 minutes thereafter.
Industry for Use High Voltage Switches (10 Kilovolt)
Volume 10,000
Delivery/Turnaround Time 2 day
Standards Met Customer Specifications, Drawing #A6503-N
Product Name Spark Arrestor Tablet

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