Introduction

Most process data of equipment and instruments are in fact Properties of the Stream inside that equipment or instruments. Yet in many cases the application software does not take streams into account.

Since ISO 15926 aims to model as correctly as possible, such Properties shall be attributed to a Stream whenever that is the case.

This topic presents a recommended way of representing such stream-related models.

Stream and Stream Segment

Some properties of streams have a gradient magnitude from source to destination, and streams have points of interest along their path, such as at the inlet of a pump. Any such point of interest is modeled as "stream segment" that is a part of a stream or part of another stream segment.

Location and time

Due to the nature of a stream it is important to specify any stream information as valid at a particular location, e.g. at the inlet of a pump, thereby using the template PropertyOfStreamAtRelativeLocation.

A stream or stream segment can be contained in any piping, equipment, or in-line instrument or a part thereof. To model that the template ClassOfContainmentDefinition (for edm:ClassOfStream) or ContainmentOfAnIndividual (for an individual dm:Stream) can be used. However, those templates do not offer the possibility to indicate the exact location, unless a stream segment at that location is declared.

This can be illustrated with the following example.

The advantage of this approach is that concepts like 'outlet pressure' can be fully modeled as, in this case, the 'pressure' of the stream segment that is contained in the outlet of the plant item of which it is the 'outlet pressure'. This in contrast with deriving the location from the English text. What about Ports?

A Fluid Port is a ClassOfFunctionalObject defined in the RDL as: "An 'opening' in a 'fluid container' for the entry or egress of substances which behave as fluids, i.e. gases, liquids and fluidized solids."

In order to remain practical, the instances of ClassOfInanimatePhysicalObject whose members function as a fluid port are made a specialization of rdl:RDS2195064321. Don't instantiate ports as such, see also here