Are Hot Isostatic Pressing (HIP) Accidents Common?
Yesterday we had a news item about an explosion in a “HIP” furnace at a location in the USA “Massive “HIP” Explosion at USA Commercial Heat Treater”, this story prompted us to look into the history of any accidents in the “Hipping” industry.
“Wikipedia” describes the process thusly; “Hot isostatic pressing (HIP) is a manufacturing process used to reduce the porosity of metals and increase the density of many ceramic materials. This improves the materials’ mechanical properties and workability. HIP is also used to bond either metal powder or ceramic powder into shapes via powder metallurgy HIP, or PM-HIP.
The HIP process subjects a component to both elevated temperature and isostatic gas pressure within a high-pressure containment vessel, unlike cold isostatic pressing (CIP), where the component is kept at room temperature.[1] The pressurizing gas most widely used is argon. An inert gas is used so that the material does not chemically react. The choice of metal can minimize negative effects of chemical reactions. Nickel, stainless or mild steel, or other metals can be chosen depending on the desired redox conditions. The chamber is heated, causing the pressure inside the vessel to increase. Many systems use associated gas pumping to achieve the necessary pressure level. Pressure is applied to the material from all directions (hence the term “isostatic”).”
In layman’s terms we can say that the process is only used in high value applications such as aerospace and medical and that the cost of entry (ie; the initial cost of the equipment and the high maintenance costs) restrict the process to just a handful of companies. Chief among them are “Bodycote” followed by “Aalberts Surface Technologies”, “Pressure Technologies Inc.” and “Kittyhawk Inc.”, although there are certainly others.
It would appear that Hot Isostatic Pressing (HIP) accidents are rare but typically severe due to the extreme pressures (up to 30,000 psi) and temperatures (up to 2,000°C) involved. Reported incidents fall into two categories, suffocating due to inert gas leaks (ie; Argon) or vessel failure. The only reported incidents we have been able to find in North America include these three examples below, two of which involve suffocating with the third being a vessel failure;
In short it would appear that “HIP” accidents are far less common than other accidents in the heat treatment industry but they certainly have the potential of producing a far larger “bang” than other furnaces if something goes wrong.
The attached photo shows a typical “HIP” installation.
