PERD Instrument Loop Taxonomy


PERD Taxonomies provide a fundamentally sound structure to capture and understand what the raw data means or represents. The taxonomy defines quality data, failure modes, causes, mechanisms, data field formats and other key performance indicators. The PERD taxonomies:

  • Help determine the “Right” data to collect
  • Provides standard industry taxonomy, data field formats and validation
  • Provides standard failure modes based upon rigorous and methodical functional analysis
  • Provides intelligent inference of failure modes

The Instrument Loop level taxonomy was created using the CCPS PERD taxonomy development work process, for inclusion within the overall CCPS PERD database structure.


The objective of this taxonomy is to present the different inventory and event tables containing fundamental data fields as well as the failure logic rules and possible key performance indicators that can be derived from the data corresponding to the Instrument Loop level database structure


This taxonomy was developed based on the methodology established in the AIChE CCPS Guidelines for Improving Plant Reliability through Data Collection and Analysis and further refined in the CCPS PERD document PERD-TAX001, CCPS PERD Taxonomy Development Guideline. An overview of the major steps to completion is listed below:

  1. Define the system
  2. Perform a functional analysis to identify and define failure modes
  3. Specify the inventory-related fields
  4. Document Key Performance Indicators
  5. Develop event data fields, creating and documenting the rule set needed to link event data fields/combinations to failure modes or successes

Instrument Loop Failure Modes

Complete Failures

  • Control Output Saturated High
  • Control Output Frozen
  • Control Output Saturated Low
  • Process Variable Indication Saturated High
  • Process Variable Indication Frozen
  • Process Variable Indication Saturated Low
  • Display of controller output indication > 100% of range
  • Control Output Indication Frozen
  • Control Output Indication Saturated Low
  • False Discreet Indication
  • Alarm Fail to Function
  • Inadequate Alarm Response Time
  • Alarm Spuriously Function
  • Interlock Fail to Function
  • Interlock Spuriously Function

Partial Failures

  • Control output high
  • Control output low
  • Control output slow to respond
  • Control output too fast
  • Control output erratic
  • Auto controller in manual mode
  • Process variable indication high
  • Process variable indication low
  • Process variable indication erratic
  • Control output indication high
  • Control output indication low
  • Control output indication erratic
  • Alarm function delayed
  • Interlock function early
  • Interlock function delayed
  • Interlock voting channel fail to function
  • Interlock voting channel spuriously  functions