An Operations and Maintenance Information Open System Alliance

Graphical Representation of Process Areas

Two important engineering drawings and knowledge transfer constructs are Process Flow Diagrams (PFD) and Piping and Instrumentation Diagrams (P&ID). These drawings contain visual information and important metadata information about the logical location of a process area and equipment usually organized in a hierarchy defined by an engineering design system. Ideally, the engineering design system's plant location hierarchy can be mapped to the ISA 95/ISA 88 hierarchy site area, Work Center or Process center functional location, and segment breakdown for equipment. Doing this provides more flexibility and enables a more granular organization and access for information. PFDs and P&IDs are the primary means to convey how the different process areas of a refinery or chemical process work and relate to each other. P&ID drawings are an extremely important visual training and diagnostic aid to engineers and operators. Unfortunately, contrary to its importance, P&ID information is rarely passed in a consumable, electronic manner as a staged means to organize information loads for operational systems or as repeatable visually rendered means for bringing clarity in the operational and maintenance field to personnel. P&IDs are a critical training and reference tool.

The most important information conveyed by PFDs and P&IDs are the equipment connection relationships, requiring support for:

  • Process stream definitions. Note this means defining the contents and process properties. Process stream definitions can change flowing through devices that only change physical properties like heat exchangers; however, the process stream name remains intact. When process streams go through mass transfer devices or chemical reactors however, then new process stream names, contents, and physical properties are designated.
  • Major and minor process piping segment definitions with flow directions and "From-To" nodal specifications for process equipment and instruments.
  • Piping segment definitions for tubing, capillaries, filled diaphragm systems for process segment connections to instrument measurement
  • On page and off page symbol notations usually accompanied with incoming and outgoing process stream definitions.
  • Piping network and piping segment definitions delineating connections nodes to equipment and instruments. Note this must support the concept of flow nozzles on equipment.
  • Pipe connectors or taps for fluid process connections to instrument measurement elements
  • Instrument Probe Connectors for instrument probe attachments to piping - process equipment
  • Instrument signals connections defining how process operating values are measured, distributed to other instruments or humans, controlled, and process manipulative elements, requiring support for:
    • Input to transmitters from continuous measurement elements flow, pressure, temperature, etc.
    • Input to measurement value Alarms or measurement value switches
    • Input to relay devices from signal threshold devices binary level switches, pressure switches, temperature switches which trip to on/off, true/false, when a measurement value is above a high limit or below low limit
    • Output from controllers to throttling control valves
    • Output from relays to (on/off) or (open/close) valves or other binary devices
    • Output from relays to limit or got to preset values to throttling control valves
    • Output to linear or variable speed devices dampers, AC or DC motors, etc.
  • Instrument measurement elements connections to process equipment or piping requiring support for:
    • Low level electrical connections from measurement elements to transmitters
    • Measurement element connection for minor tubing, capillary tubes, filled diaphragm systems for process connections for differential pressure or process pressure measurement elements
    • Instrument insertion probes for pH, conductivity, vibration, thermal conduction thermowells, etc. with from-to connectivity
    • Analyzer sampling connections
    • Inline flow elements
    • Low level electrical connections from measurement elements to transmitters
    • Mechanical/drive connections for speed and position elements

The second most important information conveyed by PFDs and P&IDs are the graphical representations of process equipment and instrumentation equipment along with key parameters and information available for each process equipment item. This provides a very rich set of provenance for the equipment item that is directly used to characterize the following:

  • A set of equipment identifications from the source engineering design system which references its assigned process or instrument tag and the project and sub–project
  • A set of specifications to which the equipment performs, and references to other information that optimally pegs the equipment to a descriptive commodity or to a defined reference library
  • A graphic representation name with a full definition of the graphic outline along with a key to cross reference for the symbols. Each graphic representation has a defined origin and pixel defined boundary and an indicator as to its position in the drawing and its orientation (e.g. flipped horizontally or rotation)
  • A notation of where process flow and instrument measurement connections can be made, and other types of connections points such as nozzles for sampling, pressure measurement, or the insertion of instrument measurement element probes for temperature, pH, conductivity, etc.
  • A revision number connoting the latest modification state of the equipment or instrumentation
  • Ultimately these equipment parameters should provide a means to access the engineering design specifications and ultimately asset specifications for each piece of equipment or instrumentation from the engineering design system or procurement system

Traditionally engineering applications systems have never transferred PFD and P&ID information other than as human readable documents in viewing formats like PDF. Basically these are set piece documents that in themselves do not yield any value for engineering data handover. Export of data has been largely a proprietary export of reference data elements organized as the author of the export interface designed.

Recently, significant progress has been made leveraging the ISO 15926 standards effort to output them via XML, RDF, or OWL-based electronic encoding. One of these mechanisms is the result of the PCA/Fiatech Proteus Project. The Proteus project was formed to provide ISO 15926 data exchange of intelligent P&ID data between vendor engineering design systems, exchange of data between different vendors, 2D P&IDs and 3D models. This was a significant step to accomplish the challenge of engineering data transfer for a large subset of the P&ID information required to bootstrap or initially load operational and maintenance systems. However, additional specification work must be added to this export method to accomplish the transfer of the full set of engineering data needed to provide all services for the operations and maintenance environment to provision/configure applications and for management of change. The goal is to identify a method to populate a common interoperable register and O&M engineering data repository using a small set of methods for all engineering design applications.