The AMETEK Model 933 UV Analyzer is a sophisticated instrument designed for continuous monitoring of hydrogen sulfide (H2S), carbonyl sulfide (COS), and methyl mercaptan (MeSH) levels in pipeline quality natural gas. It employs non-dispersive ultraviolet (UV) photometric analysis combined with AMETEK Western Research’s proprietary frontal elution chromatography system. This integrated approach ensures accurate gas analysis by effectively separating and eliminating interfering species from the sample stream. The analyzer is microprocessor-based, which simplifies its operation and management.
Function Description:
The core of the Model 933 Analyzer's operation involves UV photometric analysis. It utilizes two ultraviolet light sources (source lamps) to generate UV light. This light passes through a Chopper Wheel (also referred to as a Filter Wheel), which contains up to six interference filters. A Beam Splitter then directs the light through front-surfaced mirrors and into a Gas Measuring Cell. The gas sample flows through this cell, and the UV light interacts with the target species (H2S, COS, MeSH). Finally, two matched Photodetectors measure the light intensity, allowing for the determination of gas concentrations.
The sample conditioning system, mounted on the analyzer's backpan, plays a crucial role in maintaining constant pressure and temperature, and conditioning the sample gas for accurate analysis. Key components of the sample system include:
- Sample Probe: Extends into the sample stream to collect a representative sample.
- Pressure Regulator: Adjusts sample gas pressure to the analyzer's operating pressure (typically 80 PSIG/550 KPAG).
- Pressure Gauge: Used for setting the proper sample pressure.
- Solenoid Block: Manages gas flow between Zero, Column A, and Column B solenoids, and includes a pressure relief valve.
- Column Switching Solenoids: Automatically switch sample gas between columns for conditioning.
- Zero Solenoid: Flushes the sample system with Zero gas during Auto-Zero or Span processes.
- Column Block: Where the frontal elution chromatography takes place, using proprietary material for correct sample analysis.
- Heat Exchanger Block: Reduces the temperature of the conditioned gas sample before it enters the Measuring Cell.
- Measuring (Sample) Cell: A chamber with optical-grade quartz windows through which the radiation beam passes.
- Flow Indicator (Rotameter): Provides a visual indication of the sample flow rate.
- Filterblock Assembly (optional): Removes condensables and particulates from the sample gas through three filtration stages.
Important Technical Specifications:
- Methodology: Non-dispersive ultraviolet analysis with frontal elution chromatography.
- Target Species: Hydrogen sulfide (H2S), carbonyl sulfide (COS), and methyl mercaptan (MeSH).
- Full-Scale Ranges (Standard Measuring Cells, 40 cm or Smaller):
- H2S: 4,000 / (Cell length) PPM maximum; minimum ranges are 1/4 of maximum.
- COS: 20,000 / (Cell length) PPM maximum; minimum ranges are 1/5 of maximum.
- MeSH: 10,000 / (Cell length) PPM maximum; minimum ranges are 1/5 of maximum.
- Full-Scale Ranges (Low Range Measuring (White) Cell Option, 81.2 cm):
- H2S: 0–5 PPM minimum and 0–50 PPM maximum.
- COS: 0–25 PPM minimum and 0–250 PPM maximum.
- MeSH: 0–15 PPM minimum and 0–100 PPM maximum.
- Response Time (excluding external sample system):
- H2S: Typically < 30 seconds to T90.
- COS: Typically < 60 seconds to T90.
- MeSH: Typically < 180 seconds to T90.
- Accuracy:
- ± 2.0 % full-scale for Standard Ranges (Cells 40 cm or smaller).
- ± 5.0 % full-scale for Low Range option (White Cell, 81.2 cm).
- Repeatability: ± 2.0 % full-scale of standard ranges (including Column effects).
- Linearity: ± 2.0 % full-scale of standard ranges.
- Stability (Noise): 1.0 % of standard ranges (excluding cross-talk effects).
- Sensitivity: 0.5 % of standard ranges.
- Cross-Talk (H2S measurement): < 2 % of the sum of COS and MeSH concentrations.
- 24-Hour Zero Drift (with Auto-Zero disabled):
- Standard Range: < 2.0 % full-scale or equivalent of 10 °C Temperature Drift.
- Low Range: < 5.0 % full-scale.
- Electrical Requirements:
- Maximum Start-Up Power: < 500 W.
- Supply Voltage/Maximum Current: 120 VAC, 50/60 Hz, 3 A Max (ATEX/CSA); 240 VAC, 50/60 Hz, 1.5 A Max (ATEX); 104-132 VAC, 50/60 Hz, 3 A Max (CSA); 208-264 VAC, 50/60 Hz, 2 A Max (CSA).
- Sample Gas Flow Rate: Max 20 NLM (42.4 SCFH) for High Pressure/Low Range Kit.
- Zero Gas: Instrument zero purity Carbon Dioxide, UHP Nitrogen, or UHP Methane.
- Ambient Limits:
- Temperature: 0 °C to 50 °C (32 °F to 122 °F).
- Humidity: 0–95 % RH (environmental purge option required if > 70 % RH).
- Maximum Altitude: 2000 m.
- Sample Pressure Requirement: Max Cell Pressure 1380 kPag (200 psig).
- With Filterblock: 830–13 790 KPAG (120–2000 PSIG).
- Without Filterblock: 830–20 700 KPAG (120–3000 PSIG).
- Physical Dimensions (on Backpan): Height 1185 mm (46.65"), Width 780 mm (30.7"), Depth 254 mm (9.97").
- Weight: Approx. 100 kg (220.5 lb).
- Approvals and Certifications: CSA (Class I, Division 1, Groups C and D, Ex d IIB T3), ATEX (II 2 G Ex db IIB+H2 T3 Gb or Ex db IIB T3 Gb), IECEx (Ex db IIB+H2 T3 Gb or Ex db IIB T3 Gb), GOST, PED, EMC (EN 61326 Industrial), LVD (EN 61010-1), RoHS (2011/65/EU).
Usage Features:
The Model 933 Analyzer is designed for indoor operation and requires installation in a location free from vibrations. It communicates with a computer via the AMETEK System 200 Configurator Software, which provides a user interface for configuring operating parameters, controlling functions, and viewing live and historical data.
- Configurator Software: Allows users to set up communication parameters, modify device settings (e.g., temperature control for Optical Bench, Measuring Cell, Column Block), configure output signals (analog outputs, digital communication, digital inputs), and manage calibration parameters.
- Auto-Zero/Manual Zero: The analyzer can perform automatic or manual zero adjustments using Zero gas to maintain accuracy.
- Span Gas Calibration: Allows for manual spanning of individual gas species.
- Analog Output Calibration: Current and voltage outputs can be calibrated to ensure accurate data transmission.
- Modbus Communication: Supports RS-485 for customer data acquisition and remote service.
- Temperature Control: Maintains stable operating temperatures for the Optical Bench and Column Block to ensure consistent elution times and prevent condensation.
- Alarms and Diagnostics: Features a built-in alarm detection system that monitors key parameters, indicating Fault or Warning conditions through relays and the Configurator Software.
Maintenance Features:
Preventive maintenance is crucial for optimal performance and longevity of the analyzer. The manual outlines a schedule for various tasks:
- Every 6 Months: Check and replace Zero Gas cylinders, inspect and replace air filters for sheltered systems.
- 9–12 Months: Replace UV Source Lamps. Lamps may need earlier replacement if alarms like "Warning ALC" or "Fault Lamp Failure" are triggered.
- Every Year: Replace o-rings and clean interior surfaces of the Measuring Cell. More frequent cleaning may be required based on sample conditions.
- Every 2 Years: Replace Check Valves, Filters, Flow Restrictors, and o-rings in the Column Block Assembly. Replace Chopper Motor Drive Belt and Chopper Wheel Bearings in the Chopper Assembly.
- Flamepath Gap Checks: During each maintenance, use a feeler gauge to check flamepath gaps on enclosures and other components to ensure they meet specifications (e.g., 0.1 mm for Group IIB, 0.04 mm for Group IIB+H2).
- Troubleshooting Guide: Provides detailed corrective actions for various alarm conditions originating from the Host Controller and Microcontroller boards, including issues with EEPROM, output range, temperature, internal communication, and lamp failures.
- Spare Parts List: A comprehensive list of recommended spare parts for the Optical Bench, Sample System, Column Block, and fuses is provided to facilitate timely replacements.
- Technical Support: AMETEK offers technical support, aftermarket sales, and training for service technicians.
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