Overview
ISO 2186:2007 - "Fluid flow in closed conduits - Connections for pressure signal transmissions between primary and secondary elements" defines requirements for the design, layout and installation of pressure signal transmission systems. It specifies how a differential pressure signal from a primary flow device (per ISO 5167 flow meters) is safely and accurately transmitted to a secondary device (indicator, transmitter or data acquisition). The standard focuses on preserving signal integrity (no distortion or modification) while ensuring safe containment and maintainability.
Key Topics
- Safe containment and materials: Selection of appropriate materials, gaskets and fabrication to contain the fluid between primary and secondary devices; provisions for safe depressurization, flushing and on-line maintenance.
- Piping specification: Where process piping ends and instrument (secondary) piping begins; the concept of a specification break at the isolation valve and applicable national codes.
- Isolation (block) valves: Location, selection and orientation of block valves so they do not distort pressure signals; recommendations for ball or gate valves and packing considerations for corrosive or hazardous fluids.
- Valve manifolds: Typical manifold configurations for isolation, equalization (equalizer valve), venting and calibration; manufacturer orientation and integrated assemblies to reduce space and cost.
- Impulse/gauge lines installation: Keep impulse lines short, direct and equal in length; slope management to avoid traps, install liquid or gas traps where necessary; bleed/vent provisions after installation or testing.
- Hydrostatic (elevation) effects: Awareness that elevation differences and fluid density/temperature differences in impulse lines create hydrostatic pressure offsets - especially important for liquids.
- Sizing and dynamics: Annexes give guidance on impulse-line diameters for long runs (Annex A) and impulse-line dynamics (Annex B); additional annexes cover elevation head examples and figures.
Applications and users
ISO 2186 is used by:
- Instrumentation and control engineers
- Process and piping designers in chemical, petrochemical, oil & gas, power generation and water utilities
- Flow metering installers and calibration technicians
- Safety and maintenance teams planning isolation, testing and in-service verification
Typical applications include installation of differential-pressure flow meters (orifice plates, nozzles, Venturi devices), transmitter manifolds, and remote pressure sensing systems where accurate pressure signal transmission is required.
Related Standards
- ISO 5167-1 to -4 (primary flow metering devices: general, orifice plates, nozzles, Venturi)
- ISO 4006 (vocabulary and symbols for fluid flow in closed conduits)
ISO 2186 complements ISO 5167 by addressing the secondary side - impulse lines, manifolds and installation practices - to ensure reliable, accurate pressure signal transmission and reduced measurement uncertainty.
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