Since 1959 the authors have been involved in the design and system evaluation of underground insulated piping systems that distribute chilled water, steam, and high temperature water. As of the date of this paper, 272 various systems have been field inspected by excavation and physical examination, participation as expert witnesses for legal action in failure cases, and evaluation of systems.
In 1959 the failure rate in federal installations of these systems exceeded 50%. Some, such as at an Air Force base in upper New York State, were catastrophic failures. Some, such as at a Naval facility in California, were progressive over a short period of time. As a result, design criteria and prequalification test procedures were prepared that now form the basis of present day federal specifications. In response to these new criteria, manufacturers have developed new systems, modified old systems, and improved installation methods and procedures. Therefore the original design criteria need to be kept up to date as new materials, designs, and installation procedures are developed. This report reflects 27 years of inspection and evaluation of these systems and the maintainence of rigorous design criteria to provide a minimum 20-year system life.
This paper summarizes 272 evaluations of eight major types of systems. It reports the causes of failure and the importance of following clear design criteria. Rigorous enforcement of design criteria has become more important due to the resurgence in interest by municipalities in these systems. Already the authors have seen a partial return to the “low bid” concept without clear drawings and specifications to make sure that the finished system will provide a long-term life. It is hoped that the reporting of actual results of system installation will help to maintain the quality of work now prevalent in the United States.