16
continued on page 17
Setting or Verifying Flow Rate
When performing multiple-tube sampling using an adjustable low
fl
ow
holder (dual, tri, or quad), ensure the regulator has been activated and the
pump
fl
ow rate is set at 1.5 L/min. The maximum
fl
ow rate through any one
tube is 500 ml/min*. Calculate the sum of all tube
fl
ow rates. If the sum is
≤
1000 ml/min, proceed with calibration and sampling without any further
adjustment to pump
fl
ow rate. If the sum is > 1000 ml/min, set the pump
fl
ow rate 15% higher than the sum of tube
fl
ow rates.
* Back pressure across some sample tubes can be higher than average. In these instances,
the maximum
fl
ow rate of 500 ml/min per tube may not be achieved.
Before use, allow pump to equilibrate after moving it from one temperature
extreme to another.
Ensure pump has run for
fi
ve minutes before proceeding with
calibration.
Ensure the pump is set for low
fl
ow
(see Activating the Regulator,
page 11)
.
Connect the adjustable low
fl
ow holder (Figure 3, page 15) to the
pump intake (Figure 1, #13) using 1/4-inch Tygon tubing.
Insert an opened sorbent tube into each rubber sleeve of the
low
fl
ow holder (Figure 3, #3 and 4) with the arrow on the tube
pointing toward the holder.
If sampling with fewer tubes than number of ports, insert unopened
sorbent tubes in the empty ports to seal them.
Note the
fl
ow rates speci
fi
ed by each sampling method and add
them together. If the sum is
≤
1000 ml/min, proceed to the next
step. If the sum is > 1000 ml/min, multiply the total tube
fl
ow rate
by 1.15 and set the pump for that
fl
ow rate.
Connect a calibrator to the exposed end of a sorbent tube, loosen
the brass
fl
ow adjust screw on the low
fl
ow holder, and activate
the pump by pressing Flow and Battery Check.
Connect holder to
pump intake and tube
inlet to calibrator.
2
