Natural gas quality on Pakistani transmission lines, city-gate stations, custody-transfer skids and plant fuel-gas headers only stays trustworthy when hydrocarbon dew point and water moisture are written as separate measurement questions. Hydrocarbon dew point (HCDP) answers “when will C6+ start to condense at pipeline pressure?” Water moisture answers “how much H₂O vapour is in this sales-gas / transmission / fuel-gas stream?” A chilled-mirror Condumax II Dark Spot analyzer owns the HCDP question. A OptiPEAK TDL600 TDLAS analyzer owns continuous water moisture in natural gas (and biomethane). The catalogue Condumax II + OptiPEAK TDL600 combined system answers both in one footprint when operators want a single installation. Mixing those jobs with dryer dew point, QCM process moisture, or a generic “dew-point analyzer” label invents false comfort on gas-quality programmes.
This note is for pipeline, city-gate, custody-transfer, underground storage, and plant fuel-gas instrumentation teams specifying Michell Condumax II HCDP, OptiPEAK TDL600 TDLAS moisture, and the combined system. It maps practical selection to catalogue slugs michell-condumax-ii, michell-optipeak-tdl600, and secondary michell-condumax-ii-optipeak-tdl600. The angle is deliberately distinct from the site’s earlier general hydrocarbon and water dew-point overview, from Galvanic AccuLase-D1 TDLAS H₂S / CO₂ / H₂O analysis, from QMA601 QCM process moisture, and from Easidew compressed-air / dryer dew point.
Why HCDP and water moisture both matter on Pakistani gas networks
Contracts, grid codes and plant fuel-gas envelopes typically separate hydrocarbon liquid dropout from water content. Typical Pakistani contexts include:
- Transmission and custody transfer — HCDP protects metering and compressors from C6+ condensate; continuous water moisture protects dehydration performance and contractual water limits.
- City-gate and distribution interfaces — Gas quality at pressure let-down where condensation risk and water content both affect downstream networks and industrial offtakers.
- Plant fuel gas and turbine superheat control — Fuel-gas headers where hydrocarbon dew point and moisture drive superheat margins and turbine / heater integrity.
- Underground storage and export / LNG receiving interfaces — Streams where composition and moisture can swing with injection, withdrawal, blending or biomethane injection into the network.
Write two measurement questions first — HCDP (onset of hydrocarbon condensate) vs water moisture (ppmV / dew point of H₂O) — before you pick “a dew-point analyzer.” Condumax II is Dark Spot chilled-mirror HCDP; OptiPEAK TDL600 is TDLAS water moisture in NG; the combo is both in one system. Neither is an Easidew-class dryer transmitter, nor a QMA601-class QCM process moisture analyzer, nor automatically the same framing as AccuLase-class TDLAS.
Condumax HCDP vs OptiPEAK TDLAS vs QCM vs AccuLase vs Easidew — do not conflate
| Need | Typical approach | Catalogue / note fit |
|---|---|---|
| Automatic on-line hydrocarbon dew point (C6+ condensate onset) | Dark Spot direct chilled-mirror HCDP | Michell Condumax II |
| Continuous water moisture in NG / biomethane (TDLAS) | Tuneable diode laser absorption spectroscopy | OptiPEAK TDL600 |
| Both HCDP + TDLAS moisture in one footprint | Combined Condumax II + OptiPEAK system | Condumax II + OptiPEAK combo |
| TDLAS H2S / CO2 / H2O in natural gas (Galvanic note) | TDLAS multi-component analyzer (water in ppm) | See AccuLase-D1 TDLAS note |
| Continuous QCM process / refining ppmV H₂O | Quartz crystal microbalance process moisture | See QMA601 QCM process moisture note |
| Compressed-air dryer / utility dew point | Ceramic / polymer hygrometer transmitters | See Easidew online dew-point note |
HCDP protects metering and compressors from hydrocarbon liquid dropout. OptiPEAK-class TDLAS protects contractual water limits with composition-tolerant optical moisture. QCM process moisture protects refining / petrochemical continuous ppmV duties. AccuLase-class TDLAS is a separate Galvanic H2S / CO2 / H2O analyzer. Dryer dew point protects instrument air. Many Pakistani sites need more than one of these stories — but Condumax II / OptiPEAK (and the combo) are specified when the written duties are pipeline / custody HCDP and/or NG TDLAS water moisture.
When Condumax II fits
The Condumax II provides continuous, automatic on-line hydrocarbon dew-point measurement using the patented “Dark Spot” direct chilled-mirror technique. A thermo-electrically cooled mirror is monitored optically; as the mirror cools, hydrocarbon condensation forms a detectable dark spot at the dew-point temperature, delivering objective, highly repeatable results with catalogue 0.5°C HCDP accuracy. Features include a self-cleaning mirror (no purge or cooling gas required), optional ceramic metal-oxide water dew-point measurement in parallel, Modbus RTU output, compact explosion-proof enclosure, indoor and outdoor sampling systems for gas up to about 138 barg, and compatibility with natural gas containing up to about 20% hydrogen without modification. Hazardous-area certifications include IECEx, ATEX, UKCA, cQPSus and GOST Ex.
Prefer Condumax II when the written duty is automatic on-line HCDP for natural gas processing, custody transfer, transmission monitoring, or fuel-gas superheat control; when chilled-mirror objectivity matters versus manual dew-point testing; and when sample systems must handle high line pressures. It is not a substitute for OptiPEAK / AccuLase TDLAS water moisture, not a QMA601 QCM process moisture analyzer, and not an Easidew-class dryer transmitter.
When OptiPEAK TDL600 fits
The OptiPEAK TDL600 is a tuneable diode laser (TDLAS) analyzer for automatic online moisture measurement in natural gas and biomethane, with an operating range down to about 1 ppmV. Its D-MET system is factory-ready for varying gas compositions — for example after stream blending or shale gas / biomethane injection into a network — and the non-contact optical measurement is positioned for low maintenance even with changing methane concentrations or sour gas. Catalogue positioning includes integrated sample handling, ATEX / IECEx / UKCA / cQPSus certification, and hydrogen-blend compatibility up to about 20% H₂ without modification.
Prefer OptiPEAK when the written duty is continuous NG / biomethane water moisture (glycol dehydration outlets, transmission monitoring, custody transfer, storage, offshore export, LNG receiving / re-gas, vaporized NGL, biomethane), when composition swings must not invent false moisture, and when TDLAS (not chilled-mirror HCDP, not QCM, not ceramic dryer dew point) is the specified technology.
When the Condumax II + OptiPEAK combined system fits
The combined Condumax II + OptiPEAK TDL600 system pairs Dark Spot chilled-mirror HCDP with TDLAS moisture in a single convenient footprint — so pipeline operators get the widely accepted automatic hydrocarbon dew-point method together with spectroscopic moisture measurement without two separate installations. Catalogue moisture range for the OptiPEAK side is about 1 to 1000 ppmV with ±1 ppmV class accuracy independent of gas-composition changes; HCDP range is up to about Δ55 K depression from main unit operating temperature, with direct photo-detection of hydrocarbon condensate. Prefer the combo when both parameters are contractual at the same sample point (custody transfer, transmission, city-gate, plant fuel gas) and installation space / cost favour one system.
Sample system and integration — brief but non-optional
HCDP and TDLAS moisture readings are only as good as the gas that reaches the sensors. Sample systems must manage pressure let-down, flow, filtration and (where needed) heat tracing so analyzers see representative vapour — not condensed liquid, ambient wet air, or a dead-leg. Confirm whether contractual numbers are quoted as dew point at a stated pressure, ppmV, or mg/Nm³; mixing those bases invents false comfort. Integrate Modbus (and plant DCS/SCADA) into the same gas-quality narrative as alarms, and treat analyzer diagnostics as part of the written control story. Hydrogen-blend readiness (catalogue up to ~20% H₂ on both Condumax II and OptiPEAK) only helps if future fuel mixes are written into the specification early.
Practical use cases in Pakistan
- Transmission and custody-transfer skids — Condumax II for automatic HCDP; OptiPEAK (or combo) where continuous TDLAS water moisture is also contractual.
- City-gate and industrial offtake stations — Gas quality at pressure reduction where both condensate risk and water content matter to downstream users.
- Plant fuel-gas / turbine superheat control — HCDP and moisture on fuel-gas headers feeding turbines, heaters and boilers.
- Glycol dehydration and processing outlets — OptiPEAK for continuous moisture trending; Condumax where HCDP is separately written.
- Storage, blending and biomethane injection — OptiPEAK D-MET composition handling where methane / blend changes are expected.
- Complementary stack — Keep AccuLase-class TDLAS, QMA601 QCM process moisture, and Easidew dryer dew point as separate layers where those duties are written (see related notes).
Selection and integration tips
- Write HCDP and water moisture as separate clauses — one “dew-point” label does not close both.
- Choose Dark Spot chilled-mirror for HCDP — Condumax II when automatic on-line hydrocarbon dew point is required.
- Choose TDLAS for NG water moisture — OptiPEAK when continuous optical moisture with composition handling is required.
- Prefer the combo when both parameters share one sample point and footprint.
- Own the sample system — Pressure, flow, filtration and heat tracing are part of the measurement.
- Do not substitute Easidew, QMA601, or AccuLase by habit — match technology to the written duty and manufacturer framing.
FAQ
Is Condumax II the same as a water-moisture or dryer dew-point analyzer?
No. Condumax II measures hydrocarbon dew point with the Dark Spot chilled-mirror technique. Water moisture in natural gas is a separate parameter — typically OptiPEAK TDL600 (TDLAS), AccuLase-class TDLAS, or QMA601-class QCM depending on duty. Easidew answers compressed-air dryer dew point — see the Easidew note.
When does OptiPEAK TDL600 fit Pakistani natural gas duties?
When you need automatic online water moisture in NG or biomethane with TDLAS (down to about 1 ppmV), D-MET composition handling, sour-gas compatibility, Ex certification, and hydrogen-blend tolerance up to about 20% H₂.
When should operators specify the Condumax II + OptiPEAK combined system?
When both HCDP and TDLAS water moisture must be measured at the same location and a single system footprint is preferred. See the combo catalogue page.
How does this differ from AccuLase, QMA601, and the general HCDP overview?
AccuLase-D1 is a Galvanic TDLAS H2S / CO2 / H2O analyzer; QMA601 is QCM process moisture for refining/petrochemical streams; the earlier HCDP / water overview is a broader primer. This note focuses on Michell Condumax II, OptiPEAK TDL600, and their combined system for Pakistan pipelines and gas plants.
Can Condumax / OptiPEAK replace a BTU / composition GC?
No. Dew point / moisture and calorific value / composition are different process parameters. Use Condumax / OptiPEAK for HCDP and water moisture; use a process GC (see AccuChrome BTU note) when energy content and composition are the written duty.
How Tetracon supports HCDP and NG moisture choices
Tetracon supplies gas analysis and industrial instrumentation for Pakistan industry, including Michell Instruments hydrocarbon dew-point and TDLAS moisture analyzers used on pipelines, custody transfer, city-gate and plant fuel-gas duties. Application support through the contact page and services team can help match analyzers, sample systems, and communications to your streams and area classifications. Start with the catalogue pages for Condumax II, OptiPEAK TDL600, and the combined system, or browse Michell Instruments on the site.
Key takeaways
Hydrocarbon dew point and water moisture on Pakistani natural gas pipelines are separate written questions. Condumax II answers automatic Dark Spot chilled-mirror HCDP; OptiPEAK TDL600 answers continuous TDLAS water moisture (including variable / biomethane compositions); the combined system answers both in one footprint. Do not conflate these with AccuLase-class TDLAS framing, QMA601 QCM process moisture, or Easidew dryer dew point. Write the measurement questions and sample-system story first, then match Condumax II, OptiPEAK, or the combo to the contractual gas-quality clauses on transmission, custody, city-gate and plant fuel-gas duties.