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The ML®670 Total Reduced Sulfur (TRS) system provides an accurate and convenient method of measuring Total Reduced Sulfur required for Emission Monitoring. The TRS system uses our specially designed TRS Dilution Sampling System combined with the T-Series® TRS analyzer to provide reliable TRS measurement.  This system can be configured as an Open Architecture Design for ease of maintenance.





​The ML®670 or 670 ®Open Architecture (OA) is a pre-engineered Continuous Emissions Monitoring System (CEMS) designed for use in EPA 40 CFR Part 60 and Part 63 compliance applications and for process control. This dilution based system can be configured to accurately measure Total Reduced Sulphur (TRS) with SO2 and O2 on a dry basis.  Additional gasses such as NOx, CO, CO2 can also be measured.

Both configurations of the ML®670 CEMS consist of a heated probe, heated sample umbilical, single bay cabinet, analyzers, control equipment, and a dilution air cleanup package.  The Open Architecture version has the dilution air cleanup package mounted on a wall instead of the cabinet.

In order to measure TRS, sample is extracted from the process, filtered and dried, and then diluted with air. Using dilution extractive principles, pressurized dilution-air is used as the motive force to provide suction that mixes a small amount of stack gas into the same dilution air stream.  The diluted sample is split between two streams.  The main part of the sample is routed to a sample manifold so gasses such as NOx and SO2 can be measured.  The TRS sample is scrubbed of any SO2 and then heated to oxidize the TRS compounds into SO2.  The resultant SO2 measurement is then equal to the TRS concentration.  An O2 sensor is located after the moisture removal, but prior to dilution in a separate stream, to provide a corresponding diluent measurement. A precision mass flow meter is used to determine an accurate, real time dilution ratio.

A programmable logic controller (PLC) performs all automatic sequencing of the sample cycle, daily calibration cycle, and back purge cycle.  During calibration mode, zero and span gases are injected into the probe head to comply with EPA calibration requirements.  Back purge air is delivered to the probe on a periodic basis to clean the heated probe filter, providing months of continued operation without maintenance.

In addition, the PLC has the ability to log fuel flows and provide the required analog outputs in units of diluent corrected ppm concentration (ppmc), lb/mmBtu, and lb/hour. Standard relay outputs that signal system status and fault information are also generated from the PLC.  A RegPerfect® Data Acquisition System (DAS) may be attached to the PLC via Ethernet to provide long term data collection, compliance report generation, remote control and diagnostic information.

The ML®670 is a self-contained system requiring single point attachment for power, instrument air, and calibration gases.  All utility distributions are routed through the ML®670 internally. No duplication of utilities is required on the stack.


  • EPA certifiable for all 40 CFR 60 and 40 CFR 63 applications.
  • Well suited to generate reliable and accurate process control information.  Typical applications include recovery furnaces, industrial sources, and power boilers.
  • State of the art TML T-Series® analyzers are utilized for pollutant monitoring.  This allows a single source for system as well as analyzer support.
  • Automatic, local and  remote initiation of any system sequence is available. This includes the ability to zero and span a single analyzer both through the entire sampling train or directly at the analyzer to diagnose sampling system anomalies.
  • Minimal maintenance is required. Weekly manual calibrations, quarterly probe checks, and quarterly filter changes are typically all the system requires to achieve uptime of 95% or greater, and
  • Self-diagnosing alarm package.  The ML®670 will alarm the user for sample train heater failures, dilution air delivery problems, probe and analyzer faults.  This system is smart enough to protect itself during a fatal fault condition ensuring no moisture can contaminate any analyzer.
  • Hazardous area classification model available to meet Class 1, DIV1/2 requirements.​



Standard 316L Stainless Steel or Hastelloy probe straw
EPA approved lengths

2 micron filter standard, other sizes available

Heated probe filter maintained above 250°F [121°C]

Insulating jacket provided



¼" [.95 cm] Teflon calibration line

½" [0.64 cm] Polyethylene backpurge line

14 AWG triad for probe heater power

Fire retardant jacket



3/8" [0.95 cm] Teflon or 316 Stainless Steel sample tube

Recommended maximum length 250 feet [76.2 meter]

Line temperature controlled to 300°F [148°C]

Low temperature alarm provided to Controller

Insulated fire retardant jacket



Thermo-electric cooler

Negligible loss of SO2

Teflon diaphragm pump

Peristaltic moisture drain pump

2 micron Teflon sample filter

Water slip alarm, sample dew point alarm

Probe and sample line vacuum alarm



Single bay, 19" [48.3 cm] Rack Mount

Standard NEMA 12 with fan ventilation or HVAC.

Other NEMA ratings are available.

Dimensions 81"H x 25"W x 39"D [2.0 x 0.6 x 1.0 meter]  Approx. 400lbs.[181Kg]

Front door and rear doors, removable side panels, sight glass available

Lifting lugs and/or castors can be provided



Open rack with optional desk.

Dimensions  80"H x 63"W x 30"D [2.0 x 1.6 x 0.8 meter] Approx. 300lbs. [136Kg]

Sample Conditioning Plate.

28"H x 24"W x 9"D [0.7 x 0.6 x 0.2 meter] Approx. 60 lbs. [27Kg]



GE or Allen Bradley Controller, C3io provides data buffering, digital inputs, digital outputs, analog inputs, analog outputs, and Ethernet communications.  Optional HMI provided for manual system control.



Model Number T102, for TRS with external convertor

Zirconium Oxide Sensor for O2



SO2           0-5000ppm

O2             0-100%

TRS           0-10ppm



± 20% of Reference Methods for 40 CFR 60/63



Less than 90 seconds to 95% full scale from system inlet



Zero and Span

± 0.5% absolute for O2%         

± 2.5% of full scale for TRS  ppm


REPEATABLILITY:  ± 1% of full scale

PROCESS:  80-1800°F [27-982°C] , up to 50% moisture

AMBIENT:  Varies by Engineered Enclosure

SYSTEM UTILITIES:  -40°F [-40°C] dew point instrument air, 80 psig [551.6 KPa] minimum, 0.5 SCFM [14 lpm] , Single point attachment of 240Vac, single phase, 60 hertz, 50 amp power



  • Regulatory Consultation
  • LightHawk® 560 Opacity Monitor integration
  • LaserHawk® 360 Particulate Monitor integration
  • Ultraflow 150 Ultrasonic Stack Flow integration
  • Automatic Cylinder Gas Audits
  • RegPerfect® Data Acquisition System
  • Training
  • Installation supervision
  • Startup
  • EPA Certification
  • Maintenance Contracts​​


  • Pulp, paper and wood products
  • Oil, gas and petrochemical
5/22/2018 2:47 PMJon Adams
5/22/2018 2:47 PMJon Adams
3/21/2019 3:55 PMJack Pearson
5/22/2018 2:48 PMJon Adams