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STM-12B Mercury Sorbent Trap Monitoring System

STM-12B Mercury Sorbent Trap Monitoring System

The automated STM-12B MercSampler™ for Sorbent Trap Monitoring Systems is designed for continuous dual sampling of vapor-phase mercury emissions from stationary combustion sources, in accordance with the U.S. EPA MATS published in 40 CFR, Part 60-63, Appendix A, Subpart UUUUU and Performance Specification 12B.

The Apex Instruments STM-12B MercSampler™ simplifies most sampling requirements by automating data acquisition, sample flow adjustments, leak checks, calculations, temperature control, and calibrations. Data is easily transferred to a Microsoft Windows based PC through Ethernet, USB or an optional Wireless Interface. The STM-12B MercSampler™ captures all data necessary for paired sorbent trap sampling in accordance with PS 12B. The sample flow rate is controlled proportionally to the stack flow rate and determines the standardized volume extracted through each sorbent trap. To collect the samples, two diaphragm vacuum pumps which work with the proportional valves and mass flow sensors, pull the samples through sorbent traps.

All applicable components are rated 120V/60Hz or 240V/50Hz.

SKU: STM-12B Category:


Performance Specification 12B – Specifications and Test Procedures for Monitoring Total Vapor Phase Mercury Emissions from Stationary Sources Using a Sorbent Trap Monitoring System – EPA Literature PDF


Sampling Unit:

  • Fully Automated Paired Sampling.
  • Proportional Flow Control.
  • Customer Configured Alarms.
  • Dual Gas Meters with Optical Encoders (1cc resolution).
  • External Inputs: Stack Flow, Remote Pause, Moisture Analyzer.

Stirling Cooler:

  • Robust, closed, dual-channel gas conditioning system.
  • Cools Gas to Constant Dew Point.
  • Removes Moisture & Acid Gases.
  • Uses Acid Scrubbing Sorbent.

Heated Sample Probe:

  • Dual-Trap Probe.
  • Dual Zone Heater.
  • Insulated Junction Box.
  • Stack, Trap & Probe Thermocouples.
  • C276 Alloy (Hastelloy).
  • Cam-lock port connecter.

Heated Umbilical/Sample Line:

  • Heavy Duty, Lightweight.
  • Self-Regulated.
  • Replaceable Sample Lines.
  • Flexible, robust construction with High Temperature Jacket.


  • Powder Coated Aluminum.
  • Easy Access Door.
  • Durable Compact Design.
  • Optional Heating & Cooling System.

STM-12B Page VisualSTM-12B Page Visual 3STM-12B Page Visual 2


  • Dry Gas Meters:
    • Model SK25EX series, positive displacement type.
    • 0.7 liter per revolution.
    • Optical encoder sensor with quadrature    pulse output.
    • 8 digit LCD Display, 1 cc resolution.
  • Sample Pumps:
    • BTC Diaphragm, Brushless Motor – 12 Vdc, 20” Hg Vacuum, 10,000 hour MTBF, 3900 RPM, Max. PSIG 24”.
  • Sample Flow Control:
    • Stainless steel sample manifolds fitted with mass flow sensors, vacuum sensors, and   proportional valves.
    • Proportional or constant flow sampling.
    • Mass Air Flow: proportional flow control, 100 to 2000 ccm, port style, manifold mount.
    • Proportional Valve: Voltage Sensitive   Orifice (VSO), 12 Vdc.
  • Data Acquisition Control Board (DAC):
    • Enhanced Flash 16 bit RISC based microcontrollers;   main and Digital Signal Processing (DS). Real time   clock with auto backup and write protection to   external SRAM.
    • High Speed 14bit A/D convertor with parallel   DSP interface.
    • SD Memory Card for data storage – stores up to 99 tests (30 day test runs). Embedded Ethernet Port with full TCP/IP Protocol and 256 bit encryption.
    • USB 2.0 Comm Input connection.
  • Thermocouple Multiplexer:
    • Accepts Type K Thermocouple inputs; input protection  includes gas discharge tubes for ESD and surge protection.
    • 11 Pic Microcontrollers, 1 for each channel & MUX circuitry
    • MUX Circuitry to receive multiple inputs and transmit   selected output.
    • 10 microcontrollers, one for each optically isolated channel.
  • Integrated Temperature Control:
    • Designed into DAC for probe/trap heat control output via 25 amp SSR.
  • Barometric Pressure:
    • 600 to1100 mbar, 17.7 to 32.4”Hg, temperature compensated, amplified output.
  • Vacuum:
    • 0 to 30” Hg, 0 to 101 kPa, 2% accuracy.
  • Communications:
    • PC user interface via Ethernet
    • Remote access and control via onboard   configurable router to owners Network Computer.
    • Optional TCP/IP MODBUS (ASCII or RTU) Communications to the DAS.
    • Optional interface to DAS system via TCP/IP Modbus.
  • Weight:
    • 34 lbs. (15.5 Kg).
  • Dimensions:
    • HxWxD 14” x 19” x 15.5” (35.56 cm x 48.26 cm x 39.37 cm).


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