Encyclopedia of Environmental Science and Engineering, Volume I and II

STACK SAMPLING 1105

the probe liner is regulated with a variable voltage controller.

The controller is calibrated by introducing air at various tem-

peratures in the range of the stack temperature and deter-

mining the controller setting necessary to maintain the probe

temperature required by the Method (120 
 14ºC) or the

specific regulation, such as a subpart of 40 CFR Part 60. The

probe liner, with the heating element, is inserted in a stain-

less steel tube.

The probe liner is cleaned in much the same way as the

nozzle. Once it has cooled it is removed from the train and the

ends wiped free of silicone grease and covered. During clean-

ing, the probe is loosely held on an incline with utility clamps.

The probe is then rinsed with acetone while slowly rotating

the probe. A nylon brush, extended with teflon tubing, is used

to scrub the inside of the probe liner. The acetone is saved in

the bottle labeled Container 2 for later analysis.

Pitot Tube

A type S pitot tube is secured to the outside of the probe.

The pitot tube was discussed in the Method 2 description.

The special relationship to the nozzle is critical, in terms of

both the location and the alignment. The pitot tube should

be inspected before and after each run to insure that it has

not been damaged. The pitot tube and the tubing connecting

it to the manometer should be leak checked before and after

each run. This can easily be done by slipping rubber tubing

over the end of one side of the pitot, blowing gently on the

rubber tubing producing at least 3 inches water pressure, then

clamping the rubber tubing with a pinch clamp. No change

in pressure should be observed in 15 seconds.

Filter

The filter holder is made of borosilicate glass with a glass

frit filter support and silicone rubber gasket. Clamps of vary-

ing designs are used to seal the filter between the two halves

of the holder.

The filter is a glass fiber filter capable of capturing at

least 99.95% of 0.3 micron particles. Filters, desiccated at

room temperature and ambient pressure, are weighted every

six hours until the change is less than 0.5 mg. This process

is called desiccating to constant weight. Alternatively the

filters can be dried in an oven to constant weight. They are

allowed to cool to room temperature in a desiccator before

each weighing.

After the test, the filters are inspected for signs of gases

passing around the edges of the filter and for water stains

on the filter. Either would seriously compromise the results.

The filter is carefully transferred to a petri dish. Any pieces

of filter sticking to the housing are removed with forceps or a

sharp instrument. The front half of the filter holder is rinsed

with acetone and the acetone saved in the bottle labeled

Container 2 for later analysis.

The filter holder must be maintained at 120 
 14ºC, or

as specified in the applicable regulation.

Any heating system capable of providing this tempera-

ture around the filter holder during the run is acceptable.

TEMPERATURE SENSOR

TEMPERATURE

SENSOR

PROBE

PROBE

PITOT TUBE

PITOT MANOMETER

TYPE S

PITOT TUBE

ORIFICE

THERMOMETERS

DRY GAS METER AIR TIGHT

PUMP

MAIN VALVE

BY-PASS VALVE

IMPINGERS ICE BATH

VACUUM

GAUGE

HEATED AREA

STACK

WALL

THERMOMETER THERMOMETER

FILTER HOLDER

VACUUM

LINE

CHECK

VALVE

IMPINGER TRAIN OPTIONAL, MAY BE REPLACED

BY AN EQUIVALENT CONDENSER

Schematic of Method 5 sampling train.

FIGURE 6 Schematic of Method 5 sampling train.

C019_003_r03.indd 1105C019_003_r03.indd 1105 11/18/2005 11:07:15 AM11/18/2005 11:07:15 AM