LEV Fume Flow

Overview

A UK high-performance polymer manufacturer needed flow measurement on a Local Exhaust Ventilation duct carrying solidifying process fume. Quality Lab Solutions assessed four measurement technologies — including our own SIL-capable QMASS Coriolis range — and advised the one that fits the medium, not the one that fits the catalogue.

The challenge

The duct was rated 0–5,000 m³/h (nominal 2,601 m³/h), running at slight vacuum around 750 mbar absolute and up to 250 °C. The extracted fume changes phase as it cools, solidifying into fibrous material at the measurement point — and the installation demanded SIL-rated instrumentation.

• Tolerate fume that solidifies into fibrous, deposit-forming material.
• Measure reliably at around 750 mbar absolute and elevated temperature.
• Meet the site's SIL functional-safety requirement.
• Remain maintainable without shutting down the LEV system.

Our solution

We compared differential-pressure, ultrasonic, Coriolis and thermal-mass measurement against one criterion: tolerance to solidifying, fibrous media. Our QMASS Coriolis meters are functional-safety assessed to IEC 61508 (Systematic Capability SC 3 — SIL 2 capable in 1oo1 and SIL 3 in 1oo2 architectures), so a certified Coriolis option existed in our own range — but a vibrating-tube meter in a duct of fibrous, coating fume is the wrong instrument no matter whose name is on it. We advised against our own product on the medium and specified an insertion thermal-mass arrangement instead.

• Selection driven by the fouling failure mode, not the catalogue.
• Insertion thermal-mass with sensor purge specified for the duty.
• Retractable hot-tap mounting for inspection without shutdown.
• Carrier-air mass flow measured — the parameter LEV performance depends on.

Results

The customer received a complete, site-ready selection specification driven by the process reality, and wrote to thank us for a "suitable and appropriate" recommendation. When the duty suits Coriolis, the QMASS range covers 360 kg/h to 480,000 kg/h with SIL-capable functional safety; when it doesn't, we say so.

Customer benefits

• Selection based on the medium's failure mode.
• SIL requirements addressed honestly.
• A maintainable measurement strategy for fouling service.
• Confidence that recommendations aren't catalogue-driven.