API PUBL 334:1996 pdf download.A Guide to Leak Detection for Aboveground Storage Tanks
This booklet examines many of the known AST leak detection technologies in their generic forms. Its purpose is to demonstrate not only how to select a workable leak detection method but also how to select the technology that is best suited to a particular application. It is also intended as a tool for understanding the uncertainties associated with advanced leak detection technologies. One other type of AST leak detection methodology is where specific tank bottom and foundation designs are used. As these undertank leak detection designs are cov- ered in detail in API Standard 650, they are not discussed in this document. This method of leak detection dealing with tank bottom and foundation designs can only be installed at the time of tank construction or during a major renovation. However, the leak detection methods described in this report can typically be installed on most tanks dur- ing normal operations. has the potential to supplement the regular internal and external inspections that are standard in the industry. Leak detection in ASTs is also regulated by some state and local authorities. All of the leak detection methods discussed in this booklet can provide results on a periodic basis, and some can accommodate continuous monitoring. AST owners have three important tasks when imple- menting a leak detection program: (1) to select a type of leak detection technology or technologies, (2) to select specific systems based on those technologies, and (3) to develop a strategy for using those systems. Managers, operators and engineers are urged to explore a range of options before making these decisions.
The concept of performance as a way to measure the effectiveness or reliability of a leak detection system evolved from research on underground storage tanks (USTs). Although performance measures for AST leak detection are yet to be implemented, many of the same general concepts are expected to be applicable. Perfor- mance is defined in terms of the probability of detection, or P,, which is the likelihood that a test will detect a real leak, and the probability of false alarm, or Pf,, which is the likelihood that a test will declare the presence of a leak when none exists. A related issue is the probabilio of missed detection, or Pmd, which is the likelihood that a test will not find a leak that does exist.