Process Analyzer Sampling Guide

Most analyzer problems are sampling problems. This guide explains how to design, check, and maintain sampling systems for reliable analyzer operation.

Golden rule: If the sample is wrong, the analyzer will be wrong — no matter how good the analyzer is.

Sample Take-Off Point

  • Locate in a representative, well-mixed process zone
  • Avoid dead legs and low-flow areas
  • Provide block and bleed valves

Pressure Control

  • Use proper pressure regulators (no needle valves)
  • Avoid regulator hunting
  • Vent regulators safely and continuously

Moisture & Condensation

  • Maintain temperature above dew point
  • Use heat tracing where required
  • Install drains at low points

Filters & Coalescers

  • Install filters upstream of regulators
  • Use coalescers for wet gas service
  • Never allow liquid to reach the analyzer

Flow Control

  • Use capillaries or flow restrictors
  • Avoid manual throttling valves
  • Ensure stable, laminar flow

Common Field Mistakes

  • Calibrating during flow alarms
  • Ignoring wet sample conditions
  • Over-tightening fittings causing leaks
  • Blaming analyzer electronics prematurely
Field truth: Fix the sampling system first. Most analyzer alarms disappear without touching the analyzer.