TABLE OF CONTENTS A service interruption is defined here as a deviation from product and/or delivery specifications for a sufficient duration to cause an impact on a customer. The definition implies the existence of a specification (an agreement as to what and how delivery is to occur), a time variable (duration of the deviation), and a customer. These will be discussed in more detail later. Terms and phrases such as specification violations, excursions, violations of delivery parameters, upsets, specification noncompliances, and off-spec will be used interchangeably with service interruption.
Assessing the risk of service interruption is more complicated than assessing the risk of pipeline failure. This is because pipeline failure is only one of the ways in which a service interruption can occur. Service interruptions also have a time variable not present in the risk of pipeline failure. An event may or may not lead to a service interruption depending on how long the event lasts.
Note that ensuring an uninterruptible supply often conflicts with ensuring a failure-proof system. The conflicts occur when erroneous valve closures or equipment failures cannot be tolerated and steps are taken to make shutdowns more difficult. In so doing, necessary, desirable shutdowns are also made more difficult. This often presents a design/philosophy challenge, especially when dealing with pipeline sections close to the customer where reaction times are minimal.
This module is a parallel version of the overall risk assessment methodology. In fact, the basic risk assessment model is a part of the risk...
