Compressed-air dryers and process-gas lines only protect equipment and product quality if you can prove dew point at the outlet and at critical use points. On Pakistani refining, chemical, pharma, textile, power, and industrial sites, “the dryer is running” is not a moisture-control story — a live dew-point reading (and alarms into DCS/PLC) is.
This note is for plant, HSE, and instrumentation teams specifying online dew-point monitoring for compressed air and process gases. It maps practical selection to two catalogue Michell Instruments products available through Tetracon — the Easidew Online Dew-Point Hygrometer (sensor + sample block + configurable 1/8 DIN display) for general continuous monitoring with local readout and alarms, and the Easidew PRO I.S. Intrinsically Safe Moisture Transmitter for rugged, hazardous-area process gas (and non-polar liquid) duties. Brief selection context for the loop-powered Easidew EA2 and dedicated Easidew I.S. transmitters is included where it clarifies stocked options. It is deliberately distinct from the site’s notes on portable dew-point hygrometers, field calibration, trace-moisture technology comparison, hydrocarbon/water dew point in natural gas, and moisture in hydrocarbon liquids.
Why online dew-point monitoring matters
ISO 8573-1 class targets, instrument-air quality specs, and process-gas dryness limits only hold if moisture is measured continuously where the risk lives. Typical Pakistani plant contexts include:
- Compressed-air dryer outlets — Refrigeration, membrane, and adsorption (desiccant) dryers serving Class 1–6 duties; continuous dew point catches breakthrough, valve faults, and purge failures before tools, instruments, and product see wet air.
- Instrument and utility air — Control valves, transmitters, and pneumatic panels fail silently when condensate freezes or fouls — online dew point at the dryer and selected headers is cheaper than repeated instrument damage.
- Process and specialty gases — Inert, welding, medical, and process feed gases where ceramic metal-oxide transmitters cover −110 to +20 °Cdp class ranges without chilled-mirror complexity on every point.
- Hazardous-area process moisture — Natural-gas production, CNG drying, pipeline drying, and petrochemical streams that need intrinsically safe transmitters rather than a safe-area panel display alone.
Write the duty (panel display + alarms vs 2-wire IS transmitter), the dew-point range and alarm limits, sample pressure, and whether the location is hazardous-area classified — before you pick “a dew-point meter.” Online systems and portable spot-check hygrometers answer different questions on the same moisture programme.
Online system vs transmitter vs portable — what each is for
| Need | Typical approach | Catalogue fit |
|---|---|---|
| Continuous dew point with local display, analog/Modbus, dual relay alarms (safe-area panel / dryer room) | Complete hygrometer kit: sensor + sample block + 1/8 DIN monitor | Easidew Online |
| Rugged 2-wire IS transmitter for demanding process gas (or non-polar liquid) in classified areas | Ceramic moisture transmitter, Ex ia, high pressure rating | Easidew PRO I.S. |
| Simple loop-powered transmitter for Class 1–6 compressed-air / industrial gas (safe or I.S. variant) | 2-wire 4–20 mA ceramic transmitter | Easidew EA2 / Easidew I.S. |
| Spot checks, dryer surveys, SF6 / multi-point portable verification | Portable hygrometer | See portable dew-point note |
| Technology choice (ceramic vs chilled mirror vs TDL) | Application-led comparison | See trace moisture tech note |
| Hydrocarbon + water dew point on natural gas | Dedicated hydrocarbon dew-point / water dew-point systems | See NG dew-point note |
Match the instrument to the question you must answer every shift. If operations need a live local dew-point reading plus relay alarms at a dryer panel, Easidew Online is the natural frame. If the mounting location is hazardous-area classified and the duty is a rugged process transmitter into DCS/PLC, Easidew PRO I.S. earns its keep. Portable MDM300 / Easidew PDP-class tools still belong on the same programme for commissioning and multi-point surveys — they complement online points rather than replace them.
When Michell Easidew Online fits
The Easidew Online is a universal, quick-to-install hygrometer system supplied complete with a 2-wire Easidew ceramic metal-oxide sensor, sample block, and configurable 1/8 DIN display. Catalogue performance covers −110 to +20 °Cdp (−100 °Cdp variant), accuracy ±2 °Cdp, 4–20 mA or 0–20 mA output, Modbus RTU over RS485, dual configurable relay alarms, AC or DC supply options, and a traceable 13-point calibration certificate. The monitor processes dew point or moisture content (scaled ranges such as −110 to +20 °Cdp or 0–3000 ppmV); sensor operating pressure is listed to 525 barg with typical sample-block flow 1–5 Nl/min.
Prefer Easidew Online when you want an out-of-the-box continuous system with local display and alarms at a dryer room, instrument-air panel, or safe-area process point; when field-reconfigurable outputs via the display menu matter more than a bare transmitter; and when Class 1–6 compressed-air or general industrial gas monitoring is the primary duty. It is not a substitute for an intrinsically safe process transmitter in Zone 0 / Division 1 locations — keep PRO I.S. / Easidew I.S. for that — and it is not a portable survey tool.
When Michell Easidew PRO I.S. fits
The Easidew PRO I.S. is a rugged, high-accuracy 2-wire intrinsically safe dew-point transmitter for trace-moisture measurement in demanding process and refinery applications, in either gases or non-polar hydrocarbon liquids. Catalogue features include −110 to +20 °Cdp range (−100 °Cdp variant), accuracy ±1 °Cdp (+20 to −60 °C) / ±2 °Cdp (−60 to −110 °C), ATEX / IECEx / UKCA / cQPSus / TR CU Ex certification, 525 barg pressure rating, 316 stainless-steel housing with IP66, screw-terminal wiring via M20 gland, and a traceable 13-point calibration certificate. For gas duty it can scale dew point to ppmV using a programmed fixed pressure; liquid duty (PRO LQ I.S.) uses factory saturation constants for ppmW.
Prefer PRO I.S. when the sample point is (or may be) hazardous-area classified; when natural-gas production, pipeline drying, CNG, LNG, or petrochemical process moisture needs a process transmitter rather than a panel hygrometer; when 525 barg-class pressure and rugged mechanical packaging matter; or when one platform must cover gas and non-polar liquid moisture. Keep Easidew Online when the primary need is a safe-area display with relay alarms at a dryer panel.
Optional: Easidew EA2 and Easidew I.S. for transmitter-only duties
Where a simple loop-powered transmitter is enough — without the Online monitor kit — the Easidew EA2 covers Class 1–6 compressed-air dryers and industrial gas duties (−110 to +20 °Cdp, ±2 °Cdp, 4–20 mA, optional I.S. variant). The dedicated Easidew I.S. is the intrinsically safe transmitter for flammable gases and non-polar liquids with global Ex ia certification. Use EA2 / Easidew I.S. when DCS/PLC needs a 2-wire dew-point loop and a separate local display is not required; step up to Easidew Online when operators need the panel readout and dual relays at the dryer; step up to PRO I.S. when the process environment and certification package demand the heavier transmitter platform. Browse the full Michell Instruments range on the site.
Sample conditioning — brief but non-optional
Ceramic dew-point sensors measure the sample they are given. Condensation, liquid carryover, oil aerosol, and dead legs invent moisture or slow response. For dryer and process duties, keep sample tubing short and clean, control flow (typical sample-block guidance 1–5 Nl/min), filter particulates, and decide whether to measure at line pressure or after a controlled let-down. Compact sampling blocks and modular systems (for example Michell Easidew Sampler / ES20-class kits where applicable) reduce joints and lag. Treat the sample system as part of the analyzer — invented dew point is an expensive false alarm.
Practical use cases in Pakistan
- Adsorption / desiccant dryer outlets (Class 1–3) — Continuous Easidew Online at the dryer panel with dual relay alarms; portable spot checks after tower changeover or purge anomalies.
- Refrigeration and membrane dryer monitoring (Class 4–6) — Online dew point confirms the dryer still meets the written ISO 8573-1 class; EA2-class transmitters suit multi-point OEM dryer packages.
- Instrument-air headers — Online or transmitter loops on critical headers feeding control valves and analyzer houses; protect against condensate-related instrument failures.
- Hazardous-area process gas / CNG / pipeline drying — Easidew PRO I.S. or Easidew I.S. for classified sample points into DCS/PLC.
- Pharma, textile, and packaging compressed air — Documented dew-point limits for product and machine protection; Online for the main dryer, portable for satellite use points.
Selection and integration tips
- Write range and class targets first — °Cdp vs ppmV, ISO 8573-1 class, and trip setpoints before the purchase order.
- Panel kit vs bare transmitter — Need local display + dual relays → Easidew Online; need 2-wire into DCS only → EA2 / I.S. / PRO I.S.
- Area classification — Safe-area dryer rooms can use Online; Zone 0 / Div 1 process points need PRO I.S. or Easidew I.S.
- Own the 4–20 mA / Modbus / relay story — Dew-point alarms belong in the same DCS/PLC narrative as dryer purge and instrument-air pressure.
- Calibrate on a written rhythm — Traceable certificates plus field/lab calibration catch drift and sample-system faults early.
- Do not conflate duties — Online compressed-air dew point is not hydrocarbon dew point on sales gas, not moisture-in-liquids, and not a portable-only programme.
FAQ
Can a portable hygrometer replace Easidew Online on a dryer?
No for continuous control and alarms. Portables (MDM300 / Easidew PDP-class) are for spot checks, surveys, and commissioning. Continuous dryer and instrument-air duties need an online system or fixed transmitter with a live signal into the control system.
When is Easidew Online the better first buy than PRO I.S.?
When you need a complete sensor + sample block + local display with dual relay alarms in a safe-area dryer room or instrument-air panel, and hazardous-area Ex ia packaging is not required at that point.
When should we choose Easidew PRO I.S. instead?
When the sample point is hazardous-area classified, the process is high-pressure or mechanically demanding, or you need a rugged IS transmitter platform for gas (or non-polar liquid) moisture into DCS/PLC without a panel hygrometer kit.
Where do EA2 and Easidew I.S. fit?
As simpler 2-wire transmitter options for Class 1–6 compressed air and industrial gases (EA2), or dedicated intrinsically safe transmitter duties (Easidew I.S.), when a full Online monitor kit is not required.
How Tetracon supports online dew-point choices
Tetracon supplies dew-point and moisture instrumentation for Pakistan industry, including Michell ceramic hygrometers and intrinsically safe transmitters used on compressed-air dryers and process-gas duties. Application support through the contact page and services team can help match online systems and transmitters to your dryer classes, instrument-air headers, and classified process points. Start with catalogue pages for Easidew Online, Easidew PRO I.S., optionally Easidew EA2 and Easidew I.S., or browse Michell Instruments on the site.
Key takeaways
Online dew-point monitoring for compressed air and process gases on Pakistani plants is about proving dryer outlet and process moisture continuously — with local alarms where operators need them, and with intrinsically safe transmitters where the area classification demands them. Use Easidew Online for complete panel hygrometer duties; Easidew PRO I.S. for rugged hazardous-area process moisture; EA2 / Easidew I.S. when a simple 2-wire transmitter is enough; and keep portable hygrometers for surveys. Write range, class targets, and area classification before the purchase order, protect the sample path, and own the dew-point signal in the same control story as the dryer.