Indicator capsule construction and sensitivity

Helix Process Challenge Devices (Helix-PCDs) consist of a tube, which is at one end closed with a capsule hosting a chemical indicator. The sensitivity to detect insufficient air removal, leaks or non condensable gases (NCG) in steam depends besides the material on all geometric dimensions of the test system:

• 1. Tube length

  Tubes become more difficult to penetrate steam the longer they are. One end closed tubes are almost equal to penetrate as tubes at double length with both ends open.

• 2. Tube diameter

  In contrast to what most of experts believe, tubes at the same length become more difficult to penetrate when the diameter increases (a 1 mm diameter tube is much easier to penetrate than an 8 mm diameter tube of the same material and length). The scientific background of this phenomenon is described in the publication of U. Kaiser and J. G