ZS8100-HF Process Hydrogen Fluoride Analyzer

Potroom fugitive HF typically sits between 0.05 and 5 ppm, with the OSHA PEL at 3 ppm as an 8-hour TWA and EU BREF abatement targets driving post-GTC stack concentrations into sub-ppm territory. The ZS8100-HF is sized for that envelope — the 0–10 ppm range covers fugitive potroom duty, the 0–50 ppm range handles GTC inlet excursions, and the 0–500 ppm range handles pot-start and feed-failure events. The <0.05 ppm detection floor is claimed as fugitive-useful, not as a trace-metrology figure; the achievable number in a real potroom depends on path length, sample-line cleanliness and the baseline fluorides background (HF ≠ total fluoride). Total-fluoride sampling (particulate + gaseous via EPA Method 13A / 13B or ISO 15713) is the reference for compliance reporting; the TDLAS provides the continuous HF-only trace that feeds the control loop.

Hastelloy C-276 is a Ni-Mo-Cr alloy containing 15–16 % molybdenum. Anhydrous and low-moisture HF attacks the Mo component via fluoride-complex formation, pits the surface and then leaches Mo into the sample — unacceptable for both instrument longevity and sample integrity. Monel 400 is a Ni-Cu alloy with no reactive Mo content and is the industry reference for HF-wetted service (refinery alkylation loops, HF storage, semi acid-etch vent). Internal tubing uses PTFE or PFA to reduce HF wall adsorption at low ppm, since HF is sticky on bare metal relative to HCl. HCl does not share the Mo-attack chemistry, so the ZS8100-HCl uses Hastelloy C-276 where weldability and strength at high temperature matter more. HF and HCl SKUs therefore look mechanically similar but cannot share sample paths.

Semi etch exhaust sits downstream of a wet scrubber where HF is typically held below 1 ppm in the vent, with abatement targets approaching single-digit ppb depending on fab commitments and local permitting. The ZS8100-HF is claimed as low-ppm / fugitive-useful with a <0.05 ppm detection floor — the TDLAS can reach this range on an optimised heated-path configuration, but delivering repeatable ppb performance needs extended-path optics, PFA-lined sample lines, dedicated zero-gas discipline and a longer averaging window, all of which are scoped project-by-project as a Conditional engineering-review path rather than a default catalogue configuration. Fabs that require continuous sub-ppb audit typically co-deploy a dedicated trace instrument (cavity ring-down, ion-mobility, or ion-chromatography on a scrubber take-off) alongside the TDLAS loop.

HF has its strongest ro-vibrational structure in the 2.4–2.7 μm fundamental band and a strong overtone near 1.27 μm. The 1.27 μm overtone is the industry-preferred TDLAS window because telecom-grade near-IR diode lasers, InGaAs detectors and optical components are mature and field-rugged; the 2.5 μm fundamental is stronger per line but demands mid-IR lasers and detectors that are costlier and less robust in plant environments. At 1.27 μm the selected HF line sits in a valley between H2O continuum features, and the TDLAS tuning across the line centre at MHz-scale resolution resolves HF from adjacent H2O, CO2, SO2 and HCl absorbers. Broadband NDIR photometers can struggle on stack matrices where water and acid gases are all present.

A UV-DOAS (differential optical absorption spectroscopy) long-path alternative is specified for long-path stack geometries — flue ducts with open-path insertion, multi-point averaging or large-bore geometry where extractive sampling is impractical. UV-DOAS trades the low-ppm fugitive sensitivity of TDLAS for better integration over long open paths, so it is positioned as the stack-geometry option rather than a potroom fugitive option. Electrochemical HF sensors (ppb-range) are widely used for single-point safety alarm on alkylation loops but are a consumable, drift-prone technology with aggressive cross-sensitivity to HCl, Cl2 and SO2 — appropriate for personal / area-alarm F&G duty, not for reference-method process or CEMS measurement. GESHINE tracks EC HF safety as a Conditional engineering-review path so application engineering can confirm the fit before it is bundled into a self-branded catalogue.