THE BEOWN-DUVEL MOISTURE TESTER 
25 
Table 3. 
■Variations in gas pressure affect the heating time and cause varia- 
tions in moisture test results 
[Excessive pressure results in too fast heating time and too high moisture test. Burners adjusted to 
1.2 inches gas pressure] 
Gas pressure 
Average 
Maxi 
mum 
Minimum 
Range 
Average error 
from correct 
method 
Heating 
time 
Mois- 
ture 
Heating 
time 
Mois- 
ture 
Heating 
time 
Mois- 
ture 
Heating 
time 
Mois- 
ture 
Heating 
time 
Mois- 
ture 
Inches 
1.2 
Min. 
17 
13 
11 
10 
17 
Per cent 
11.7 
12.1 
12.3 
12.6 
11.7 
Min. 
18 
14 
11 
10 
17 
Per cent 
11.9 
12.4 
12.7 
13.0 
11.9 
Min. 
16 
12 
10 
9 
16 
Per cent 
11.6 
11.8 
12.0 
12.1 
11.6 
Min. 
2 
2 
1 
2 
1 
Per cent 
0.3 
0.6 
0.7 
0.9 
0.3 
Min. 

-4 
-6 
-7 
Per cent 

2.2 
.4 
3.2 
.6 
3.6 
.9 
Correct (1.2 inches) 
with gas regulator 
Note. — Data given in this table summarize 18 tests for each gas-pressure series on the same sample of 
Conversely, if the burners are adjusted to give the correct heat- 
ing time at a higher gas pressure on the supply lines and the gas 
pressure decreases, a corresponding increase in the time of heating 
and a decrease in moisture results. Such variation in pressure must 
be overcome to give accurate results. 
GAS PRESSURE REGULATOR 
Variations in gas pressure can be overcome by the use of a gas 
pressure regulator, commonly called a gas governor. One type of 
gas governor is shown in Figure 1, attached to a moisture tester, 
and diagrammatically in Figure 20. 
In operation, the gas pressure regulator, when once correctly ad- 
justed, will deliver gas to the burners of the tester at a constant pres- 
sure regardless of pressure variations on the gas supply line, or of 
variations in the number of burners in operation simultaneously; 
whereas, without the use of a gas pressure regulator, it is necessary 
for correct and uniform moisture test results to adjust the gas valve 
which regulates the gas supply (pressure) to the burners of the 
moisture tester at different periods of the day and to adjust the 
flame for every burner still in use each time that one of the burners 
is cut off. 
Table 4 gives the correct size of gas pressure regulator for moisture 
testers having varying numbers of burners. The table also gives 
the various sizes of gas supply lines to be used and the minimum gas 
pressure on the supply lines at which the regulators will operate. 
The size of regulator and pipe lines for moisture testers should con- 
form to the specifications given in the table to insure against possible 
overtaxing of the gas supply. 
The regulator may be installed at any place on the gas supply line 
between the meter and the moisture tester, although it is desirable 
to place it as close to the tester as is possible. A gas pressure regula- 
tor, however, is not capable of compensating for changes in the 
British thermal units, or for changes in the density of the gas sup- 
plied the consumer. If these change, the heating time will change. 
and the burners in the moisture tester will have to be restandardized. 
