WESTERN RESEARCH 900ADA Oxygen Analyzer

Overview

The WESTERN RESEARCH 900ADA Oxygen Analyzer is a high-stability, extractive gas analysis system engineered for continuous, real-time monitoring of dissolved and gaseous oxygen in demanding industrial process environments—particularly within sulfur recovery units (SRUs) and tail gas treatment systems. Despite its designation as an “oxygen analyzer,” the 900ADA is functionally integrated into a broader multi-component gas analysis platform, where it operates in concert with complementary analyzers (e.g., UV/Vis spectrometers or GC-based modules) to deliver coordinated measurement of critical sulfur species—including H₂S, SO₂, COS, CS₂, and elemental sulfur vapor (S_v). Its core oxygen sensing technology employs a galvanic electrochemical cell optimized for long-term drift stability, wide temperature tolerance (−10 °C to 50 °C ambient), and resistance to poisoning by acidic or sulfur-laden sample streams common in Claus plant off-gas. The analyzer is designed for permanent installation in hazardous area classified zones (Class I, Div 1, Groups B–D per NEC/CEC), with optional ATEX/IECEx certification available upon configuration.

Key Features

• Galvanic electrochemical O₂ sensor with field-replaceable, sealed electrolyte cartridge—no external power required for sensor operation.
• Integrated sample conditioning system including heated sample line (up to 180 °C), particulate filtration (0.1 µm sintered metal), and pressure-regulated flow control (300–1000 mL/min).
• Auto-zero and span calibration capability via programmable solenoid valves; supports manual or automated calibration using certified N₂ and air standards.
• 4–20 mA analog output with HART® v7.5 protocol for integration into DCS/PLC systems; optional Modbus TCP/IP and Profibus DP interfaces.
• IP66-rated stainless steel (316SS) enclosure with internal temperature stabilization and condensate management system.
• Embedded diagnostics including sensor health monitoring, flow verification, and fault logging compliant with ISA-84 SIS requirements.

Sample Compatibility & Compliance

The 900ADA is validated for use with sour gas streams containing up to 2,000 ppm H₂S, ≤500 ppm SO₂, and trace levels of COS and CS₂—conditions typical of SRU tail gas prior to thermal or catalytic oxidation. Sample dew point is actively managed to prevent condensation-induced corrosion or sensor fouling. All wetted materials (including Teflon™-lined sample path, Hastelloy C-276 fittings, and ceramic filters) are selected for chemical inertness toward sulfur compounds and chloride-bearing contaminants. The analyzer complies with applicable sections of ISO 14644 (cleanroom compatibility for service access), CSA C22.2 No. 142 (explosion-proof construction), and meets electromagnetic compatibility (EMC) requirements per EN 61326-1. It supports audit-ready data integrity practices aligned with FDA 21 CFR Part 11 when deployed with approved software configurations.

Software & Data Management

The embedded firmware provides local display via a 4.3-inch resistive touchscreen with multilingual UI (English, Spanish, French). Configuration, calibration history, and alarm logs are stored internally for ≥12 months (timestamped, non-volatile memory). Optional Process Instruments’ PI-View™ software enables remote monitoring, trend analysis, and report generation (PDF/CSV export) with configurable alarm thresholds and email/SNMP notification. All calibration events and parameter changes are recorded with user ID, timestamp, and reason-for-change fields—supporting GLP/GMP documentation requirements. Data export formats conform to ASTM E1461 and ISO/IEC 17025 traceability frameworks.

Applications

• Real-time O₂ trim control in Claus furnace and thermal oxidizer air/fuel ratio optimization.
• Monitoring of residual O₂ in tail gas prior to SCOT or SuperClaus™ units to prevent catalyst deactivation.
• Verification of inerting effectiveness during SRU shutdown and commissioning procedures.
• Integration into advanced process control (APC) loops for sulfur balance modeling and emissions compliance reporting (EPA 40 CFR Part 60, Subpart JJJJ).
• Support for ISO 14064-1 greenhouse gas quantification where O₂ concentration correlates with combustion efficiency and CO₂ emission factors.

FAQ

Is the 900ADA certified for use in Zone 1 hazardous areas?

Yes—when configured with appropriate explosion-proof housing and intrinsically safe barriers, it meets ATEX II 2G Ex db IIB+H2 T4 Gb and IECEx Ex db IIB+H2 T4 Gb standards.
Can the 900ADA measure oxygen in high-H₂S streams without sensor poisoning?

The galvanic cell design incorporates a selective hydrophobic membrane and acid-resistant electrolyte formulation, enabling stable operation at H₂S concentrations up to 2,000 ppm with mean time between failures (MTBF) exceeding 24 months under typical SRU conditions.
Does the analyzer support automatic zero/span calibration with plant air and nitrogen?

Yes—dual calibration gas inlets with solenoid-controlled sequencing allow unattended daily or weekly calibration routines, with full audit trail logging in accordance with ISO/IEC 17025 clause 7.7.
What is the recommended maintenance interval for the oxygen sensor cartridge?

Under continuous operation at 25 °C and <50% relative humidity, the standard cartridge has a rated service life of 18 months; replacement intervals are dynamically adjusted based on accumulated exposure hours and diagnostic health metrics.
Is third-party validation data available for sulfur species cross-sensitivity?

Independent testing conducted per ASTM D6299 protocols confirms interference from SO₂ < ±0.1% FS and from H₂S < ±0.05% FS across the 0–25% O₂ measurement range.