ISO 5667-7:1993

Overview

ISO 5667-7:1993 - "Water quality - Sampling - Part 7: Guidance on sampling of water and steam in boiler plants" gives practical recommendations on procedures, equipment and sample-point design to obtain representative physical and chemical samples from boiler systems. The standard covers raw water, make‑up water, boiler feed water, condensate, boiler water and cooling water, and provides guidance for sampling both saturated and superheated steam. It does not apply to nuclear power plants. ISO 5667-7 is intended to be used with ISO 5667‑1, ‑2 and ‑3.

Key topics and technical requirements

• Sampling system components: specifies the basic elements - sampling probe, sampling line, cooler (if needed), valves and sample delivery point - and recommends materials compatible with the fluid (stainless steel 18Cr‑8Ni is typical).
• Probe types and placement: describes straight (off‑take) probes for dissolved species and directional/multiport probes for particulate sampling and isokinetic sampling. For shell boilers a sample point should be at least 150 mm below normal water level; sampling should be taken during normal operation (not during firing).
• Isokinetic sampling: emphasizes isokinetic techniques where the probe inlet velocity matches stream velocity to obtain representative particulate samples, with guidance and figures for port spacing and division of pipe cross‑section (multiport probes).
• Sampling point siting: advises avoiding stagnant zones, locating points where complete mixing has occurred (downstream of pumps, bends or turbulence promoters), and preferred installation locations relative to flow disturbances (guidance on internal pipe‑diameter distances).
• Lines, valves and pressure considerations: sampling lines should be as short as practical, designed to withstand full system pressure/temperature and arranged with isolating valves and flow control; for high‑pressure systems a pressure‑reducing valve may be required.
• Sample cooling and handling: cooling is recommended for samples >50 °C; typical target temperatures after cooling are about 25–30 °C. Cooler design, materials and relief devices are discussed.
• Steam sampling: covers both single‑port and multiport probes, recommendations for saturated vs superheated steam, and minimum mass‑flow guidance (tabulated by steam pressure) to ensure representative sampling.

Applications and users

ISO 5667‑7 is used by:

• Boiler plant and power plant engineers (non‑nuclear)
• Water treatment and chemical control specialists
• Maintenance and reliability teams
• Environmental and analytical laboratories performing boiler water/steam analyses
• Consultants specifying sampling systems and procurement of sampling hardware

Practical uses include corrosion/product monitoring, chemical treatment verification, condensate and feedwater quality checks, and operational troubleshooting.

Related standards

• ISO 5667‑1, ‑2, ‑3 (sampling programme design, techniques, preservation/handling)
• ISO 6107 (water quality vocabulary)
• ISO 8199 (micro‑organism enumeration guidance)

Keywords: ISO 5667‑7, boiler plant sampling, water and steam sampling, isokinetic sampling, sampling probes, boiler water quality, sample cooling, stainless steel sampling equipment.