Many fluids transported by pipelines are in some sense hazardous. It is therefore often necessary to install leak detection (and locating) systems (LDS), especially due to legal regulations like the "Code for Federal Regulations (CFR) Title 49 Part 195" , API 1130 2nd Ed. , both for the USA, or the "Technische Regeln für Fernleitungen" (TRFL) (Technical Rules for Pipelines) in Germany . This paper gives a survey of methodologies, methods and techniques for leak detection and locating, 4] and  are two other interesting sources giving an overview of the topic. The survey starts with some remarks concerning (legal) regulations both for the USA and for Germany. Some few words about externally based systems (due to API 1130 2nd Ed.) follow next. A significant part of the paper deals with internally based systems (also due to API 1130 2nd Ed.) like balancing systems (line balance, volume balance, compensated mass balance etc.), Real Time Transient Model LDS (RTTM-LDS), pressure/flow monitoring and statistical analysis LDS. Different methods for leak locating (gradient intersection method, wave propagation analysis etc.) will also be shown. The presentation of an Extended RTTM approach (E-RTTM) combining advantages of conventional RTTM LDS and statistical analysis follows next, together with the demonstration of applicability by means of two examples, a liquid multi-batch pipeline, and a gas pipeline. Sketching future work and the conclusion conclude the survey.
Companies operating pipelines transporting hazardous fluids (e.g. liquids or gases) often have to consider a dedicated regulatory framework. Examples are
Code for Federal Regulations (CFR) Title 49 Part 195  (USA)
API 1130 2nd Ed.  (USA), and
"Technische Regeln für Fernleitungen" (TRFL) (Technical Rules for Pipelines)  (Germany).
The 2nd Edition of API 1130 "Computational Pipeline Monitoring for Liquid Pipelines" was published from the American Petroleum Institute in November, 2002, . Other regulations like the "Code for Federal Regulations (CFR) Title 49 Part 195"  refer to API 1130. The API 1130 focuses on the design, implementation, testing and operation of CPM systems; it is limited to single-phase liquid pipelines. API 1130 defines a CPM-system as an "algorithmic approach to detect hydraulic anomalies in pipeline operating parameters". The technical overview section introduces to methodologies of CPM-systems, classifying them into
externally based leak detection systems, and
internally based CPM systems, see Fig. 1. Externally based systems. Externally based systems use local sensors, generating a leak alarm. System costs and complexity of installation usually are high; applications therefore are limited to special high-risk areas, e.g. near rivers or nature protection areas. Examples for such a type of LDS are acoustic emission detectors monitoring noise levels and location and vapor sensing cables, sensing gas or hydrocarbon vapor near a leak.