SOP - Light Absorption Coefficient - Filter-based - Thermo 5012 Multi Angle Absorption Photometer (MAAP)

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CSIRO Marine and Atmospheric Research
Cape Grim Baseline Air Pollution Station
 
Thermo 5012 Multi Angle Absorption Photometer (MAAP) – black carbon /light absorption
 
Work Instruction Manual

Return to Standard Operating Procedures

Contents

Amendment Record Sheet

Amendment Officer Amendment Date Section Number Brief description of amendment
J Ward July-Aug 2008 All Initial Draft of all sections
JG, JW Dec 2008 All revision

Introduction and description

The 5012 Multi Angle Absorption Photometer (MAAP)

The Thermo Electron Corporation (Teco) Model 5012 Multi Angle Absorption Photometer (MAAP) utilises single wavelength light absorption to infer black carbon (BC) concentration, from the light absorption coefficient at a nominal wavelength of 630 nm. It uses a multi-angle absorption photometer to measure the radiation fields in the forward and back hemisphere of a glass-fibre filter caused by deposited particles. This approach allows use of aerosol radiative transfer theory to essentially remove scattering effects that otherwise impact on the derived light absorption coefficient; the data inversion algorithm takes multiple scattering processes inside the deposited aerosol and between the aerosol layer and the filter matrix explicitly into account.

For more details on the theory of operation, see Section 8 of the MAAP manual.

The Cape Grim 5012 operates with the following configuration:

            240Vac Line voltage setting

            PM-1 Size Selective Inlet (a BGI VSCC), operated at < 40% RH

            RH controlled inlet heater system set to keep sample RH to <40%

Operational flow rate is controlled to 16.67 Lm-1 (1000 litres per hour at the cyclone), at ambient pressure and cyclone temperature.

Filter advance: Auto with transmission < 20%

            Exhaust port exhausted to outside laboratory, via bench-end extractor.

Measurement Interval: RS232: 1-sec, data reported: 1-minute, further processed to 1-h statistics.

Standard conditions for reported concentrations 0 ºC, 1 atm., flow is calibrated at ambient.

During normal operation, the keyboard usually is locked. The majority of the menu points and all displays can be accessed by pressing the BACK, NEXT and YES keys. Changing operational and calibration parameters are only possible after enabling the keyboard. With the keyboard enabled only operational changes are possible. To calibrate the unit, a code must be entered to access calibration rights.

Primary Reference

Teco Model 5012 MAAP Instruction Manual for v1.2, edition 1 Dec 2003, p/n 100076-00

Work Instructions

Maintenance, Audit, Calibration Frequency Acceptance Criteria Operating Manual

Reference

Responsibility
Daily checks Daily various Whole manual
CG Staff
Weekly checks Once per week various Whole manual
CG Staff
Filter tape As needed n/a Chapter 2
CG staff
Flow Audit 3 monthly ± 0.2 Lm-1 Chapter 4 & 5
CG staff /QA visit by CMAR staff
Temp/Press/RH sensor cal 12 monthly Temp: ±1 ºC

Press: ±10 hPa

Chapter 4 & 5
CG staff /QA visit by CMAR staff
Flow Calibration 12 monthly ± 0.2 Lm-1 Chapter 4 & 5
CG staff /QA visit by CMAR staff
HEPA check 12 monthly 0 ng/m3 BC Chapter 6
CG staff /QA visit by CMAR staff

Daily checks

Purpose

This procedure describes how to perform the Daily checks.

Scope

This should be performed every day of the working week.

Reference

Teco Model 5012 MAAP Instruction Manual for v1.2, edition 1 Dec 2003, p/n 100076-00

Equipment

CG BAPS Daily check sheet.

Procedure

1.  View the Status LED’s next to the Display. A green LED next to “ready” indicates the instrument is operating normally. Red “error” LED’s indicated an instrument error that may need to be rectified. Record in check sheet.

2.  Observe the instrument display. Check if there are any instrument Status conditions or Errors present. Identifying and interpreting the error codes are described in Chapters 3 and 6 of the manual. Record in check sheet and Particles Logbook.

3.  Observe instrument output – check that data are within normal expected ranges.  In Baseline typically expect BC < 25 ng m-3 and non-Baseline typically < 100ng m-3, although many mg m-3 is possible during strong pollution, e.g. smoke, events.

3-Monthly checks

Purpose

This procedure describes 3-monthly checks, to be carried out by station staff or by CMAR staff on QA/QC visits.

Scope

The principal 3-monthly check is an audit of the MAAP inlet flow.  Flow rate in the MAAP is determined using an orifice plate located after the filter tape. The flow rate is then calculated from the pressure drop measured at the orifice plate (together with pressure and temperature), see Figure 1.

Figure 1


Reference

Teco Model 5012 MAAP Instruction Manual for v1.2, edition 1 Dec 2003, p/n 100076-00

Equipment

Station flow standard – (Gillibrator)

Procedure

Flow check as per Chapter 5 of the manual. Disconnect the inlet line from top of MAAP and attach flow audit connector (5/8” to 3/8” reduction) to enable connection to the Gillibrator. With the MAAP running take a minimum of 10 readings at 10 second  intervals on the Gillibrator.  Record the average reading in the particle log, the value should be 16.7 L m-1.  If the measured flow diverges more than ± 0.2 L m-1 from 16.67 L m-1 a flow calibration should be initiated (this will require temperature and pressure checking/calibration first).

Clean the grit-pot on the in-line cyclone and regrease lightly with silicone grease. Re-tighten “finger-tight”.

Record all test details in Particles Logbook.

12-Monthly checks

Purpose

This procedure describes annual checks, to be carried out by station staff or by CMAR staff on QA/QC visits.

Scope

The principal additional annual checks are an audit of the MAAP environmental sensors (temperatures and pressure), with recalibration if necessary, (manual also recommends check/replace pump vanes) a filter check for zero and check of the set point humidity for the SSI humidity control heater.

Reference

Teco Model 5012 MAAP Instruction Manual for v1.2, edition 1 Dec 2003, p/n 100076-00

Equipment

Reference Thermometer with an accuracy of ±0.5 ºC

Reference Barometer with an accuracy of ±5 hPa (or station barometric pressure)

Humidity Salt Solutions

Reference manometer

Procedures

1. Temperature and pressure calibration are described in section 4.3.1 of the manual.  Put MAAP into calibration mode (will require the access code: 147), scroll down to Outside temperature, measure temperature of SSI temperature sensor using the transfer thermometer.  If the difference in temperatures exceeds ±1 ºC, proceed to the recalibration.  Record details in the Particles log.

2. Scroll down to Barometric Pressure, record pressure indicated by MAAP and either station level pressure (from Obs) or from a traceable barometric sensor. If the difference in pressures exceeds ±10 hPa, proceed to the recalibration.  Record details in the Particles log.

3. Carry out flow audit, and then a zero check, also perform differential pressure sensor calibration if the flow calibration has shifted appreciably.   For the zero check attach a Hepa cartridge filter to the inlet, scroll down to the Service menu, enable the keys and proceed to open the head and advance the filter, stop the motor and close the head.  Scroll back to normal operation.  Leave the filter in place for sufficient time to determine the zero level, this can be read by scrolling down the display to give last hour, 3 hour and 24 hour averages.   It is desirable to run for at least 3 hours with filtered air to assess the noise level.  Record all information in the Particles log.

4. Calibrate the Humidity Sensor in the Inlet Heater system over several points encompassing 40% RH, and set to the Controller to activate at 40% RH. Record initial and final readings in the Particles Logbook

5. If required, replace the carbon vanes in the vacuum pump as per chapter 5 and 7 of the manual. Service the pump outside of the laboratory so that carbon dust does not contaminate the airspace.

Installing the Filter Tape

Purpose

This procedure describes how to install a new Filter Tape.

Scope

This should be performed when the instrument is first installed and/or when the previous filter tape finishes.

Reference

Teco Model 5012 MAAP Instruction Manual for v1.2, edition 1 Dec 2003, p/n 100076-00

Equipment

New Filter Tape, Teco p/n: FH111.

Double-sided sticky tape.

Procedure

1.  Follow the steps under “Filter Tape Installation” on page 2-7 of the manual, which refer to the Front View diagram on page 2-2.

2.  Be sure to check correct rotation of the spools and correct spool tension. Follow the checks in the last paragraph on page 2-7.

3.  Record in Particles Logbook that a filter change has occurred.

References

By John Gras and Jason Ward.

CMAR-CG-BAPS-MAAP5012 1st Edition

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