PFDs

PFDs is an acronym with several meanings across different fields. In safety and outdoor recreation it most commonly refers to Personal Flotation Devices, while in process engineering it denotes Process Flow Diagrams. In reliability engineering, PFD can also mean Probability of Failure on Demand, a metric used to assess safety systems. The meaning depends on context, terminology, and standards governing the specific industry.

Personal flotation devices are wearable devices designed to preserve buoyancy and keep a user afloat in water. They include life jackets, buoyant vests, and immersion suits, and are used for boating, water sports, and rescue operations. PFDs are designed to meet country-specific standards and approvals, such as the United States Coast Guard (USCG) or European CE markings. Proper selection considers activity, weight, and environmental conditions, and wearers must be trained in correct use. Regular inspection and maintenance are recommended, as devices can degrade or lose buoyancy over time.

Process Flow Diagrams are schematic representations of the major equipment, vessels, piping, and material streams within a chemical or process plant. A PFD provides an overview of how process units are connected and how data such as temperatures, pressures, and flows move through the system. It is distinct from a Piping and Instrumentation Diagram (P&ID), which adds instrumentation and control details. PFDs aid design, startup, and optimization, serving as a blueprint for mass and energy balance calculations and safety reviews.

Probability of Failure on Demand is a reliability metric used for safety systems, describing the likelihood that a safety function will fail to operate on a demand basis. It informs risk assessment, SIL ratings, and redundancy requirements, helping ensure appropriate protection against hazardous events.