HORIBA EIA-51d / EIA-51p Intrinsically Safe and Explosion-Proof NDIR Gas Analyzer
| Brand | HORIBA |
|---|---|
| Origin | Japan |
| Model | EIA-51d / EIA-51p |
| Explosion Protection | Ex d IIB+H2 T4 (EIA-51d) / Ex p II T4X (EIA-51p) |
| Measurement Principle | Non-Dispersive Infrared (NDIR) with Interference Compensation |
| Measured Gases | CO, CO₂, CH₄ (configurable per application) |
| Range | 0–0.11 vol% to 0–100 vol% (CO/CO₂), 0–50 ppm to 0–2000 ppm (CH₄) |
| Repeatability | ±0.5% F.S. (standard range) |
| Linearity | ±1.0% F.S. |
| Zero & Span Drift | ±2.0% F.S./week |
| Response Time (T90) | ≤20 s (standard), ≤40 s (extended range) |
| Sample Flow | 500 mL/min |
| Sample Pressure | ≥1.98 kPa |
| Operating Ambient | –5 to +40 °C, RH ≤90%, vibration ≤0.3 m/s² @ 100 Hz |
| Analog Output | Isolated 4–20 mA (standard), optional 0–10 V / 0–5 V / 1–5 V |
| Digital Interface | RS-485, Modbus RTU (selectable baud rates: 1200–19200 bps) |
| Wetted Materials | SUS304, SUS316, FKM, CaF₂, Au |
| Calibration | Manual (standard), Auto-calibration (optional) |
| Purge Gas | N₂, 196–690 kPa, 0.5 L/min (operational), 10 L/min (purge mode) |
Overview
The HORIBA EIA-51d and EIA-51p are certified explosion-proof process gas analyzers engineered for continuous, reliable measurement of combustible and hazardous gases—including carbon monoxide (CO), carbon dioxide (CO₂), and methane (CH₄)—in classified industrial environments. Based on non-dispersive infrared (NDIR) spectroscopy with proprietary interference-compensated optical architecture, these analyzers deliver high selectivity and long-term stability in demanding applications such as chemical manufacturing, petrochemical refining, biogas upgrading, and landfill gas monitoring. Unlike conventional single-detector NDIR systems, the EIA-51 series integrates dual-channel detection: a primary measurement channel and a dedicated reference channel operating at a wavelength insensitive to target gas absorption. This configuration actively corrects for spectral interference from co-existing gases (e.g., H₂O vapor, hydrocarbons), mechanical vibration, and optical drift caused by source aging or detector degradation—ensuring metrological integrity under real-world process conditions.
Key Features
- Explosion protection certified to international standards: EIA-51d complies with Ex d IIB+H₂ T4 (flameproof enclosure); EIA-51p meets Ex p II T4X (pressurized enclosure), enabling safe deployment in Zone 1 and Zone 2 hazardous areas per IEC 60079-0, -1, and -2.
- Interference-compensated NDIR optics with dual-detector configuration minimizes cross-sensitivity and enhances measurement robustness in complex gas matrices.
- Wide dynamic range capability: configurable spans from trace-level (0–50 ppm CH₄) to high-concentration (0–100 vol% CO₂), supporting both safety monitoring and process control requirements.
- High metrological performance: repeatability ±0.5% F.S., linearity ±1.0% F.S., and zero/span drift ≤±2.0% F.S./week—validated under ISO 14001-aligned calibration protocols.
- Industrial-grade analog and digital interfaces: isolated 4–20 mA output (750 Ω max load), plus optional RS-485 Modbus RTU communication for integration into DCS, SCADA, or MES platforms.
- Corrosion-resistant wetted materials including SUS304/SUS316 stainless steel, FKM elastomers, calcium fluoride (CaF₂) windows, and gold-coated optical components ensure compatibility with aggressive sample streams.
Sample Compatibility & Compliance
The EIA-51d/51p is designed for dry, dust-free sample gas streams with O₂ concentration ≤21% (v/v) and total pressure ≥1.98 kPa. It operates optimally at 500 mL/min flow rate and ambient temperatures between –5 °C and +40 °C. The analyzer complies with IEC 61508 (SIL2-capable architecture), IEC 60079 series for explosive atmospheres, and supports audit-ready documentation for GLP/GMP-regulated environments. While not FDA 21 CFR Part 11–certified out-of-the-box, its optional auto-calibration module and event-logged digital communications facilitate implementation of electronic record controls required under pharmaceutical and environmental compliance frameworks.
Software & Data Management
The EIA-51 series supports full remote configuration and diagnostics via Modbus RTU over RS-485, enabling centralized parameter management across multi-analyzer installations. All analog outputs include programmable alarm thresholds (–10% to +110% of signal span), while optional contact I/O modules allow hardwired interlock signaling to emergency shutdown systems. Firmware updates and calibration logs are timestamped and retain full audit trails. When integrated with HORIBA’s optional data acquisition software, users can generate compliant reports aligned with ISO 17025 calibration records and EPA Method 21–referenced leak detection workflows.
Applications
- Continuous emission monitoring (CEM) of CO and CO₂ in flue gas stacks under EN 15267 and EPA PS-15 protocols.
- In-situ biogas composition analysis (CH₄/CO₂ ratio) for anaerobic digestion optimization and renewable energy certification.
- Leak detection and fugitive emission quantification in refineries and chemical plants (ASTM D6522-compliant sampling interface).
- Safety-critical monitoring of confined spaces and reactor headspaces for CO accumulation or inerting gas purity (N₂ purge verification).
- Process gas analysis in syngas production, hydrogen reforming, and catalytic oxidation units where explosive limits must be maintained below LEL thresholds.
FAQ
What explosion protection certifications does the EIA-51d hold?
The EIA-51d is certified Ex d IIB+H₂ T4 per IEC 60079-1, suitable for use in Zones 1 and 2 where IIB-class gases (e.g., ethylene, acetone) or H₂ mixtures may be present.
Can the EIA-51p operate in Zone 0 environments?
No—the EIA-51p is rated Ex p II T4X (IEC 60079-2), permitting use only in Zone 1 and Zone 2; it is not intrinsically safe (Ex ia/ib) and therefore unsuitable for Zone 0.
Is automatic calibration available as a factory-installed option?
Yes—auto-calibration functionality is offered as an optional hardware module with integrated zero/span solenoid valves and certified reference gas ports, supporting unattended operation for up to 30 days between manual interventions.
Does the analyzer support multi-gas measurement simultaneously?
Each EIA-51 unit is configured for one primary gas component (CO, CO₂, or CH₄) at time; simultaneous multi-gas analysis requires parallel analyzer channels or integration with HORIBA’s TIA-51 series for O₂/H₂ add-on capability.
What maintenance intervals are recommended for optimal performance?
Optical path cleaning and zero/span verification are recommended every 3 months; annual full calibration using NIST-traceable standards is advised for regulatory reporting compliance.
