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Table 9—Model 58MSA Orifice Size and Manifold Pressure for Correct Input
(Tabulated Data Based on 20,000 Btuh per Burner, Derated 2% for Each 1000 Ft Above Sea Level)*
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
and
Canada
850
43
3.7
43
3.8
42
3.2
42
3.3
42
3.4
875
43
3.5
43
3.6
43
3.7
43
3.8
42
3.2
900
44
3.7
43
3.4
43
3.5
43
3.6
43
3.7
0
925
44
3.5
44
3.7
44
3.8
43
3.4
43
3.5
950
44
3.4
44
3.5
44
3.6
44
3.7
44
3.8
to
975
44
3.2
44
3.3
44
3.4
44
3.5
44
3.6
1000
45
3.7
45
3.8
44
3.2
44
3.4
44
3.5
2000
1025
45
3.5
45
3.6
45
3.7
44
3.2
44
3.3
1050
45
3.3
45
3.4
45
3.6
45
3.7
45
3.8
0%
1075
45
3.2
45
3.3
45
3.4
45
3.5
45
3.6
derate
1100
47
3.6
47
3.7
45
3.2
45
3.4
45
3.5
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
and
Canada
U.S.A.
775
43
3.8
42
3.2
42
3.3
42
3.4
42
3.5
Altitudes
800
43
3.5
43
3.7
43
3.8
42
3.2
42
3.3
2001 to
825
44
3.8
43
3.4
43
3.6
43
3.7
43
3.8
3000
850
44
3.6
44
3.7
44
3.8
43
3.5
43
3.6
or
875
44
3.4
44
3.5
44
3.6
44
3.7
43
3.4
Canada
900
44
3.2
44
3.3
44
3.4
44
3.5
44
3.6
Altitudes
925
45
3.7
45
3.8
44
3.2
44
3.3
44
3.4
2001 to
950
45
3.5
45
3.6
45
3.7
45
3.8
44
3.3
4500
975
45
3.3
45
3.4
45
3.5
45
3.6
45
3.8
5%
1000
45
3.1
45
3.2
45
3.4
45
3.5
45
3.6
derate
1025
45
3.0
45
3.1
45
3.2
45
3.3
45
3.4
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
Only
750
43
3.7
43
3.8
42
3.3
42
3.4
42
3.5
775
43
3.5
43
3.6
43
3.7
43
3.8
42
3.2
800
44
3.7
43
3.4
43
3.5
43
3.6
43
3.7
3001
825
44
3.5
44
3.6
44
3.8
43
3.4
43
3.5
850
44
3.3
44
3.4
44
3.5
44
3.7
44
3.8
to
875
45
3.8
44
3.2
44
3.3
44
3.5
44
3.6
900
45
3.6
45
3.7
45
3.8
44
3.3
44
3.4
4000
925
45
3.4
45
3.5
45
3.6
45
3.7
44
3.2
950
45
3.2
45
3.3
45
3.4
45
3.5
45
3.7
7%
975
45
3.0
45
3.2
45
3.3
45
3.4
45
3.5
derate
1000
45
2.9
45
3.0
45
3.1
45
3.2
45
3.3
*Orifice numbers 45 are factory installed.
Percents of derate are based on midpoints of U.S. altitude ranges.
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