Hervé Barthelemy

Vacuum Superinsulated Liquid Oxygen Piping and Vessels

Vacuum superinsulation is commonly used in industrial applications for liquid oxygen transfer piping and liquid oxygen vessels as an alternative to other solid insulation materials such as perlite or Foamglass®, which have lower thermal performances. Tests have been conducted on insulation materials according to ASTM D2512 (equivalent to ISO 11114–3, EN 1797) in LOX as well as according to ASTM G72 (equivalent to EN 1797) in GOX. The superinsulation materials that have been tested are a number of layers of aluminum foils of various thicknesses each being separated by intermediate nonmetallic layers of various nature. Based on experience and incidents in the industry, this paper is intended to discuss the recent test results in pure oxygen and the possible ignition of superinsulation material in the interspace and mechanism of propagation as well as the consequences of a fire. Recommendations regarding material selection for vacuum superinsulation materials in LOX applications are also provided.

Test Method for Quantifying the Ignitability of Metallic Materials

Currently, no test standard exists for quantifying the ignitability of metallic materials in oxygen. Metallic materials are consistently used at oxygen pressures significantly greater than their associated burn limits. Oxygen fires are rare in these applications; however, they still occur and the proximity to ignition and fire for applications that do not experience fire is always unknown. A new test method for quantifying the ignitability of metallic materials in oxygen is described. The method uses a powerful electric arc to deliver a quantifiable amount of energy at the surface of a metallic sample and estimate the minimum ignition energy of the material. A case example is provided in which arc ignition test results were used to evaluate the ignitability of aluminum-bronze and to help support a particle ignition risk analysis of aluminum-bronze industrial control valves.

Oxygen Fires in Aluminum Alloy Cylinders

One of the most frequently asked questions in the oxygen compatibility world is whether aluminum is compatible with oxygen. The answer is yes for high pressure aluminum alloy (AA) cylinders, and this is proven by the fact that several million AA cylinders are safely used around the world every day. However, some accidents have occurred with AA cylinders in oxygen service. In this paper, two main accident types are described and illustrated. The first accident occurred when devalving a cylinder which was under full pressure, resulting in a violent explosion and burning of a large part of the cylinder shoulder. The second accident occurred when a cylinder was dropped from a height of about 400 mm; again the cylinder exploded and again a large part of the cylinder shoulder burned. Tests were conducted in an attempt to understand the ignition mechanisms. In this paper, the ignition mechanisms are explained and recommendations are provided to prevent reoccurrences.