Michell Promet EExd Process Moisture Analyzer
Overview
The Michell Promet EExd is a complete process moisture analysis package for critical gas applications, combining one or two measurement channels, integrated electronic pressure measurement and a premium sample conditioning system in a single field-mounted flameproof installation. It measures dew point from -120 to +30 °C, equivalent to 1 ppbV to 30,000 ppmV, which allows one platform to cover everything from trace moisture ahead of cryogenic liquefaction to sales gas quality at the outlet of a glycol dehydration unit.
Seven Star LLC supplies the Michell Promet EExd to gas processing, LNG, refining and petrochemical operators in Oman and the GCC, backed by engineering support in Muscat. We help project and maintenance teams choose between the single and dual channel versions, indoor panel or outdoor enclosure layouts and the sampling system configuration that matches the process conditions at each tapping point.
Measurement Principle
At the core of the Michell Promet EExd is the Michell ceramic metal-oxide moisture sensor, produced with thick- and thin-film semiconductor techniques on metallized ceramics. The sensor responds to the partial pressure of water vapor in the gas, which relates directly to dew point temperature, and it offers sensitivity down to 10 ppbV with pressure capability up to 138 barg. According to the manufacturer, the ceramic construction is immune to the pressure shock that can damage older aluminum oxide sensors during commissioning and shutdown, and its inert nature gives strong resistance to chemical attack even in gas with percentage levels of H2S.
Each Michell Promet EExd sensor is calibrated against fundamental dew point systems in a laboratory traceable to NPL in the UK and NIST in the USA, and its calibration data is stored in on-board non-volatile memory. Integral pressure measurement lets the firmware convert dew point into moisture content, or into dew point at a different pressure, using ideal-gas data or natural gas specific methods from ISO 18453 or IGT Research Bulletin No. 8. Best accuracy is ±1 °C dew point between -59.9 and +20 °C, or ±10% of reading in moisture content terms.
Engineering Design of the Michell Promet EExd
The main unit holding the electronics and sensors is a cast copper-free aluminum flameproof enclosure, black polyester powder coated, certified for Zone 1 and Zone 2 or Class I Division 1 and 2 hazardous areas. Because it is flameproof, the Michell Promet EExd needs no barrier units or safety earth; a single low-power AC supply of 90 to 260 V feeds both the analyzer and its sampling system. The enclosure is internally temperature controlled at the normal maximum local ambient, which limits adsorption and desorption effects in sample components during day-night temperature swings, and a compensation algorithm protects accuracy if the heater fails or ambient exceeds the set point.
The Michell Promet EExd user interface is a bright vacuum fluorescent display with capacitive touch-through-glass keys, so settings can be changed without opening the housing. Each channel provides two non-isolated 4 to 20 mA outputs, one process alarm contact and one instrument status alarm, and Modbus RTU at 9600 baud gives access to all values and alarm states. A rolling log of 150 records stores time, date, moisture and pressure per channel at intervals from 5 to 60 minutes.
Key Features
Engineers typically select the Michell Promet EExd for the following reasons.
- Single or dual channel moisture measurement in one flameproof main unit, with sample pressure measured on each channel.
- Wide measuring range of -120 to +30 °C dew point, with a calibrated range of -100 to +20 °C dew point.
- Ceramic metal-oxide sensors tolerate pressure shock and remain stable in sour gas with high H2S content.
- Calibration Exchange Service lets a newly calibrated sensor be fitted with no programming, renewing calibration with minimal downtime.
- Field calibration is also possible against a portable dew point generator, a reference hygrometer or certified moisture-in-gas cylinders.
- Natural gas conversions to ppmV, lb/MMSCF and mg/m3 per ISO 18453 or IGT#8, chosen at order.
- Premium sampling systems for natural gas dehydration and for trace moisture ahead of molecular sieve beds, with custom designs available.
- ATEX, IECEx, UKCA and cQPSus certification with operating pressures up to 138 barg in the T3 rating.
Industrial Applications
The Michell Promet EExd is used where moisture control protects both equipment and product quality. Typical duties listed by the manufacturer include natural gas glycol dehydration, offshore export pipelines, transmission pipeline monitoring, LNG production, hydrogen production and storage including hydrogen injection into natural gas, ethylene feedstock to polymer plants and specialty gas production. The trace moisture sampling system is optimized for molecular sieve dehydration ahead of cryogenic liquefaction, where a particulate filter and isolation valve are the only components upstream of the sensor so the reading follows the process with minimal lag.
In Oman, these conditions are found at gas processing plants in the interior, at LNG trains in Sur, at refinery and aromatics units in Sohar, and at the hydrogen projects being developed around Duqm and Salalah. Seven Star LLC supplies the Michell Promet EExd for these sites, along with related moisture instruments such as the Michell Easidew EA2 dew point transmitter, the Easidew PRO I.S. intrinsically safe moisture transmitter and the Michell CD2-WDC-002 water dew-point sensor assembly.
Where hydrocarbon dew point is also required, consider the Michell Condumax II hydrocarbon dew-point analyzer.
Technical Specifications
The following Michell Promet EExd data is taken from the manufacturer datasheet; the exact rating depends on the selected order code and sampling system.
| Parameter | Specification |
|---|---|
| Model | Michell Promet EExd |
| Channels | Single or two channel |
| Sensor technology | Michell ceramic metal-oxide moisture sensor |
| Measurement range | -120 to +30 °C dew point; 1 ppbV to 30,000 ppmV; 0 to 250 barg |
| Calibration range | -100 to +20 °C dew point; 10 ppbV to 23,000 ppmV |
| Accuracy | ±1 °C dp (-59.9 to +20 °C), ±10% moisture content; ±2 °C dp (-60 to -100 °C), ±20%; pressure ±0.25% FS |
| Units | Dew point °C/°F; ppmV; lb/MMSCF and mg/m3 for natural gas; barg, MPa, psig |
| Outputs | Two non-isolated 4–20 mA per channel, 500 Ω max load |
| Alarms | Two volt-free contacts per channel (process and instrument status) |
| Communications | Modbus RTU, 9600 baud |
| Display / interface | Vacuum fluorescent display, capacitive touch-through-glass keyboard |
| Operating pressure | 30 to 138 barg (other variants to order) |
| Sample connections / flow | 1/8 inch NPT (F); 1 Nl/min; flow alarm standard |
| Power supply | 90 to 260 V AC, 50/60 Hz, 180 W main unit |
| Operating environment | -20 to +60 °C, max 95 %rh, shaded location |
| Enclosure | Flameproof Ex db, cast copper-free aluminum, black powder coat |
| Hazardous area | ATEX/UKCA II 2 G and IECEx Ex db IIB+H2 Gb (T5/T4 to 60 barg, T3 to 138 barg); cQPSus Class I Div 1 Groups B, C, D |
How to Order
For a quotation on the Michell Promet EExd, send Seven Star LLC the number of channels, gas type, H2S content, line pressure, expected dew point range and installation location. Download the datasheet on this page for your design review, and contact our Muscat instrumentation team about availability, sampling system options, sensor exchange planning and delivery anywhere in Oman and the GCC.
- Datasheet Michell Promet EExd Datasheet Download
Michell product families on this page
The Condumax II is an automatic hydrocarbon dew-point analyzer for natural gas. Several of its parts are listed separately: the CD2-SCR-002 hydrocarbon dew-point sensor cell, the CD2-WDC-002 water dew-point sensor assembly and the CD2-SX-WDC-002, which is the exchange version of that water dew-point sensor. The Easidew line is represented by the Easidew EA2 dew point transmitter and by the Easidew PRO I.S., an intrinsically safe moisture transmitter for hazardous areas. A ceramic impedance moisture sensor module is also listed, the sensing element behind these transmitters.Where Michell analyzers are used
Hydrocarbon and water dew point are contract quality parameters for natural gas, so the Condumax II is found at gas processing plants, pipeline entry points and custody transfer stations throughout the GCC. Easidew transmitters monitor dryers for instrument air and industrial gases, glove boxes, and dry gas feeds to processes that cannot tolerate water.Ordering Michell parts: what we need
For Condumax II parts send the analyzer serial number and the part code, such as CD2-SCR-002, and state if a new assembly or the exchange item is wanted. For Easidew transmitters we need the measuring span in dew point or ppm, the process connection thread, the output signal, the operating pressure, the gas and the area certification. A photo of the label on the old transmitter usually answers most of these in one go.Browse MICHELL Instruments products by category: Gas Analyzer Accessories, Gas Analyzer Systems.
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