Stork DEWRay Portable Chilled-Mirror Dew Point Meter

Overview

The Stork DEWRay is a field-deployable, high-accuracy chilled-mirror dew point meter engineered for trace moisture analysis in industrial process gases and compressed air systems. It implements the primary reference method for dew point measurement—chilled-mirror hygrometry—combined with Stork’s proprietary beam-splitting optical detection system. Unlike conventional cold-mirror instruments that assume ice formation below 0 °C, the DEWRay dynamically distinguishes between frost and supercooled water on the mirror surface in real time using dual-wavelength reflectance analysis. This capability eliminates systematic errors of up to 4 °C commonly observed in legacy instruments when measuring sub-zero dew points in hydrocarbon-rich or low-thermal-conductivity gas matrices. The device operates on the thermodynamic principle that dew point is defined as the temperature at which water vapor in a gas phase reaches saturation and condenses onto a cooled, polished surface—provided that condensate phase identity (ice vs. liquid) is unambiguously resolved. The DEWRay’s copper-gold-coated mirror ensures optimal thermal conductivity and spectral reflectance stability across its full operating range.

Key Features

• Beam-splitting optical detection system for automatic, real-time discrimination between ice and supercooled water—no manual observation or forced pre-cooling required
• Triple-range dew point capability: −30 °C to +90 °C (standard single-stage Peltier), −40 °C to +90 °C (dual-stage cooling), and −20 °C to +130 °C (high-temperature mode with heated mirror assembly)
• Self-cleaning mirror function via controlled thermal cycling and inert gas purge, minimizing contamination-induced drift
• Integrated 4-wire 100 Ω 1/10 DIN Class B Pt100 sensor for precise mirror temperature metrology, independently traceable to ITS-90
• Rechargeable lithium-ion battery supporting >10 hours of continuous operation at ambient conditions; hot-swappable with AC adapter (90–264 VAC)
• IP65-rated polypropylene enclosure with Swagelok-compatible stainless-steel fittings and 0.3 µm particulate filtration
• Multi-parameter display: dew point (°C/°F), relative humidity (%RH), absolute humidity (g/m³, g/kg), water activity (a_w), and temperature depression (Δt = T_gas − T_dew)

Sample Compatibility & Compliance

The DEWRay is validated for use with non-corrosive, non-condensing process gases including nitrogen, argon, helium, hydrogen, natural gas, instrument air, SF₆, and purified compressed air. It supports pressure operation from vacuum to 2.5 MPa (25 MPa optional with reinforced manifold), enabling direct inline measurement in transmission pipelines, drying skids, and gas cylinder filling stations. All optical and thermal subsystems comply with IEC 61000-6-2 (immunity) and IEC 61000-6-4 (emissions). Calibration certificates are issued with uncertainty budgets referenced to national metrology institutes (e.g., PTB, NPL) and conform to ISO/IEC 17025 requirements. The instrument meets relevant sections of ASTM D1193 (Type I–IV reagent water specifications), ISO 8573-1 (compressed air purity classes), and EU GMP Annex 1 (moisture control in sterile manufacturing environments).

Software & Data Management

Data acquisition and configuration are managed via the Stork DewControl™ PC software suite (Windows-based), supporting bidirectional communication over RS-232 or RS-485. The internal non-volatile memory logs timestamped dew point, mirror temperature, gas temperature, flow rate, and diagnostic flags at user-selectable intervals (1 s to 60 min). Export formats include CSV and XML, compatible with LIMS integration and statistical process control (SPC) platforms. Audit trail functionality records all parameter changes, calibration events, and user logins—meeting FDA 21 CFR Part 11 requirements when deployed under electronic record protocols. Firmware updates are delivered via secure USB interface with cryptographic signature verification.

Applications

• Petrochemical refining: Monitoring moisture in hydrogen reformer purge streams, ethylene cracker off-gas, and LNG dehydration units
• Power generation: Ensuring dew point compliance in turbine inlet air, SF₆ insulation gas, and hydrogen-cooled generator purge systems
• Pharmaceutical manufacturing: Qualifying compressed air per ISO 8573-1 Class 2:2:2 for Grade A/B cleanrooms and lyophilizer chamber blanketing
• Aerospace & defense: Verifying dryness of avionics purge gas, missile propulsion system purge lines, and radar waveguide pressurization
• Nuclear facilities: Moisture surveillance in primary coolant cover gas (helium/nitrogen mixtures) and spent fuel pool ventilation exhaust
• R&D laboratories: Reference-grade validation of cavity ring-down spectroscopy (CRDS) and tunable diode laser absorption spectroscopy (TDLAS) moisture analyzers

FAQ

How does the DEWRay resolve the supercooled water problem inherent in traditional chilled-mirror hygrometers?
The DEWRay employs a dual-beam reflectance photometer that monitors both specular and diffuse reflection components simultaneously. Ice and supercooled water exhibit measurably distinct scattering signatures at near-infrared wavelengths. The embedded algorithm classifies condensate phase in <100 ms without requiring manual intervention or artificial nucleation techniques.

Is the DEWRay suitable for high-pressure natural gas applications?
Yes. Standard configuration supports up to 2.5 MPa. An optional high-pressure manifold rated to 25 MPa enables direct connection to transmission pipeline taps and custody transfer stations, with pressure compensation applied to thermodynamic calculations per ISO 18453.

Can the DEWRay be used for regulatory-compliant calibration of other moisture analyzers?
Absolutely. Its primary-standard chilled-mirror architecture, combined with NIST-traceable calibration and documented measurement uncertainty (<±0.2 °C k=2), qualifies it as a transfer standard in accredited calibration laboratories per ISO/IEC 17025 Clause 6.5.2.

What maintenance is required between calibrations?
Mirror cleaning is performed automatically during each measurement cycle. Annual verification of Pt100 sensor linearity and optical alignment is recommended. No consumables—other than optional 0.3 µm filter elements—are required under normal operating conditions.