609 / 975
4
Disclaimer:
The content in this paper is loosely based on experiences, and have been embellished to bring out the salient points
against the objectives of this paper.
Project that are being engineered may include this detection to be installed, such as to meet the
requirements of these standards. The SIL determination analysis identifies when low pressure detection
is not appropriate for leak detection, and projects either change designs, or if too far into design
continue and accept the ineffective functions.
It provokes the question is leak detection activated by low pressure common sense or fallacy?
Extracts from one standard for pressure vessels and for pipelines are:
Pressure Vessels
A pressure vessel should be provided with
a PSL sensor to shut off inflow to the
vessel when leaks large enough to reduce
pressure occur, unless PSL sensors on
other components will provide necessary
protection and the PSL sensor cannot be
isolated from the vessel when in service.
Undesirable Event
= Leak
Detectable Abnormal Condition at
Component
= Low pressure
Pipelines
PSH and PSL sensors are required on departing pipelines to shut off all input sources.
Undesirable Event
= Leak
Detectable Abnormal
Condition at Component
= Low pressure
For these two examples of using low pressure as leak detection how many HAZARDOUS states would be
detected?
Low pressure detection is unlikely to detect fugitive or small releases, and also may not detect
reasonably large releases.