Plant Lifecycle Model

latest update: 30 August 2015     



This topic deals with the Lifecycle (Activity) Model of a Plant:

The data model shown below is clearly a "back bone" model. It can be seen as an integrating ontology.

First the model is shown, and then each layer is discussed.

For an implementation of this model see


Data Model

Overall lifecycle model


Process Design & Conceptual Engineering

This first part of the lifecycle has the following model:

Process Design deals with hydraulic networks, with Unit Operations and Streams of Matter and Energy. The BFD (Block Flow Diagram, source: The Engineering Toolbox and OSHA) shown below gives an example:



Participating in those Unit Operations (= ClassOfActivity) are those Stream classes (e.g. Waste Water). This can be modeled by using the template ClassOfParticipationDefinition. So in above BFD the tag P24 at Node 06 it can be seen that stream S11 participates in the role of 'input' and stream S12 in the role of 'output' (so in this case two instances of that template). See for further details the topic Process Design.

Logic Diagrams like this, are also a part of Conceptual Engineering:

Under Conceptual Engineering also belong engineering activities like Start-up Sequencing of electric motors, or also Logic Diagrams, as shown above. Such Logic Diagrams spell out the required functionality, but not its physical implementation (e.g. in software, solid state logic, or relay system).

Process design results, next to the documents already mentioned, in PFDs (Process Flow Diagram).

In fact these are more detailed Activity Diagrams, where symbols for the instances of ClassOfFunctionalObject are shown, thereby implying the ClassOfActivity that those instances of ClassOfFunctionalObject are capable of performing. Unfortunately PFDs are often mistaken for a kind of simplified P&IDs.

An important end product of Process Design is a document (or file) called Heat & Material Balance, giving all details about the streams:

Detailed Engineering

Based on the results of process design the process data for equipment, instrumentation and piping are produced. These include adaptations caused by engineering rules, such as a required overcapacity. With these data the specifications for this hardware are being written. These also include additional requirements, such as material of construction and explosionproofing .

Let us have a closer look at the applicable part of the model:

The "Ur Plant Design Tag" is a placeholder that never changes. See Life cycle of a Class.

The functionality of pump class CO_P-101 rev1 (CO_ = Class Of) is actually taken from the results of the process design, BUT... the stream data cannot be used as is, because often there are design rules that require a change to these process data. For example, the plant owner requires that pumps shall be designed with a 10% overcapacity. These adjusted process data appear in the specification, usually in terms of minimum, normal, and maximum.

The tag CO_P-101, actually a member thereof: P-101 (see Plant Design) also appears on the P&ID, showing its place in the hydraulic network, and in the 3D plant model, showing its location and details for its support and controls.

Plant Design

Schematic diagrams are being produced, like the P&IDs (Piping and InstrumentDiagram), Instrument Loop Diagrams and Electrical Schematics. Then three-dimensional plant models are made, that define the exact shapes and locations of the piping and pipe supports. From this the Isometrics for piping are produced.

Two approaches, or a mix of them, are possible here:

  1. The plant design is done at the level of instances of FunctionalPhysicalObject
  2. The plant design is done at the level of instances of ClassOfInanimatePhysicalObject

Approach #1 assumes a one-of plant, no copies directly or later. In this approach only decomposition, connection and shape information should be specified at this level. All hardware requirements are done at class level. Configuration of subsystems, like lube and seal oil systems, usually will be represented at class level because of their standardized character.

Approach #2 should be taken in case the plant design is to be standardized. In such cases the instances of FunctionalPhysicalObject will be in the role of liaison between design and reality only.


In order to be able to purchase the equipment and materials required for constructing the plant, RFQs (Request For Quotation) are issued to three or more potential suppliers. The specifications are sent with these RFQs, and on the basis of the requirements outlined by these specifications the potential suppliers offer their goods (and/or services).

After due evaluations a choice is being made and the goods are being ordered. That choice can be put on record in the following manner:

The red-marked ClassOfArrangedIndividual is a dual class-of-temporal-part of the ClassOfArrangedIndividual shown in the Detailed Engineering and the one in Procurement. It indicates that the requirements are fulfilled by the characteristics of the offered goods. There may be more than one supplier whose goods fulfil the requirements. Then a selection is made on commercial criteria.

NOTE - Keeping the complying other suppliers on record has the potential benefit of being able to quickly select a replacement in case of calameties.

The Purchase Order is placed, ordering unnamed members of the Class that represents the offering, where applicable with a reference to the tag number.

Manufacturing & Logistics

The manufacturer manufactures (or takes from his stock) a member of the offered ClassOfArrangedIndividual, and often (depending on the goods) gives that member a serial number.

After due shop inspections (where applicable) that member is shipped to the construction site. There, or later, it gets an asset number (where applicable) to register it in the plant owner's books.


The actual pump, with asset number 654321, is taken from the warehouse and a temporal part of it, is installed to fulfil the requirements of "Function Place" (a term used by SAP) 'P-101' rev1.

It is this installed item that is the placeholder for all Operations and some Maintenance) information. All equipment design and plant design information is accessible from the catalog and as well as the function place.


The installed physical objects participate in the process activities, e.g. pumping, cracking, platforming, etc and so do the handled streams.

At some time the properties and composition of the streams are being compared with the values of the process design results (see red-marked Classification with ? ). If there is a reason for it, the design may be adapted, and the life cycle starts again.


The installed physical object participates in the Activity "In-line Maintenance", the non-installed or de-installed item is particpating in the Activity "Shop Maintenance". After re-installation that re-installed physical object is a new temporal part.