Unique Solution: Large bore borosilicate glass sight tube used for visual inspection of pipelines.



A company with a unique request finds their solution thanks to the Precision Electronic Glass (PEG) team. The company needs a glass sight tube for inspecting the contents of a pipeline in the field. Additionally, the specifications create their own set of problems.

First, the sight tube needs to have a large 9-3/4˝ bore. Because of the large diameter of the tube, a heavier wall thickness is needed to withstand the internal pressure of the pipeline. Therefore, the cross section of the wall needs to be greater than one inch. However, there is no material this thick on the market. As a result, the PEG team has to come up with an innovative solution.


Due to its clarity and inert qualities, borosilicate glass is the material of choice. The PEG team sets up tooling to shrink the borosilicate glass tubing to the 9-3/4˝ diameter. With that accomplished, the PEG team solves the issue creating a one-inch cross-section of the wall for the sight tube.

The glass specialists and engineers at PEG decide to use a laminating process. It consists of fitting a smaller borosilicate glass tube inside a larger tube, fixturing them over tooling, and subjecting them to enough of a flame to fuse them together. The process is repeated until several layers of borosilicate tubing are fused together to achieve the desired thickness of one inch.

PEG Capabilities

  • Extensive Glass Knowledge
  • Engineering Experience
  • Shrinking (precision bore)
  • Decorating Capabilities