27
Table 9 – Orifice Size and Manifold Pressure (In. W.C.) for Gas Input Rate
(Tabulated Data Based on 21,000 Btuh High--Heat/14,500 Btuh for Low--Heat Per Burner, Derated 4 Percent for Each 1000 Ft.
(305 M) Above Sea level)
ALTITUDE RANGE
FT. (M)
AVG. GAS
HEAT VALUE
(BTUH/CU
FT.)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
USA
0 to
2000
(0 to 610)
900
42
3.2/1.5
42
3.3/1.6
42
3.4/1.6
42
3.5/1.7
925
43
3.7/1.8
43
3.8/1.8
42
3.2/1.5
42
3.3/1.6
950
43
3.5/1.7
43
3.6/1.7
43
3.7/1.8
43
3.8/1.8
975
43
3.3/1.6
43
3.4/1.6
43
3.5/1.7
43
3.7/1.7
1000
44
3.6/1.7
43
3.3/1.6
43
3.4/1.6
43
3.5/1.7
1025
44
3.4/1.6
44
3.6/1.7
43
3.2/1.5
43
3.3/1.6
1050
44
3.3/1.6
44
3.4/1.6
44
3.5/1.7
43
3.2/1.5
1075
45
3.8/1.8
44
3.2/1.5
44
3.3/1.6
44
3.4/1.6
1100
46
3.8/1.8
45
3.7/1.8
44
3.2/1.5
44
3.3/1.6
ALTITUDE RANGE
FT. (M)
AVG. GAS
HEAT VALUE
(BTUH/CU
FT.)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
USA
2001 to
3000 (610
to 914)
800
43
3.8/1.8
42
3.2/1.5
42
3.3/1.6
42
3.4/1.6
825
43
3.5/1.7
43
3.7/1.7
43
3.8/1.8
42
3.2/1.5
850
43
3.3/1.6
43
3.5/1.6
43
3.6/1.7
43
3.7/1.8
875
43
3.2/1.5
43
3.3/1.6
43
3.4/1.6
43
3.5/1.7
900
44
3.4/1.6
44
3.5/1.7
43
3.2/1.5
43
3.3/1.6
925
44
3.2/1.5
44
3.3/1.6
44
3.5/1.6
44
3.6/1.7
950
45
3.7/1.8
45
3.8/1.8
44
3.3/1.6
44
3.4/1.6
975
46
3.7/1.8
46
3.8/1.8
45
3.8/1.8
44
3.2/1.5
1000
46
3.5/1.7
46
3.6/1.7
46
3.8/1.8
45
3.7/1.8
ALTITUDE RANGE
FT. (M)
AVG. GAS
HEAT VALUE
(BTUH/CU
FT.)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
USA
3001 to
4000 (914
to 1219)
775
43
3.5/1.7
43
3.7/1.7
43
3.8/1.8
42
3.2/1.5
800
43
3.3/1.6
43
3.4/1.6
43
3.5/1.7
43
3.7/1.7
825
44
3.6/1.7
43
3.2/1.5
43
3.3/1.6
43
3.4/1.6
850
44
3.4/1.6
44
3.5/1.7
44
3.6/1.7
43
3.2/1.5
875
45
3.8/1.8
44
3.3/1.6
44
3.4/1.6
44
3.5/1.7
900
46
3.8/1.8
45
3.8/1.8
44
3.2/1.5
44
3.3/1.6
925
46
3.6/1.7
46
3.7/1.8
45
3.7/1.8
45
3.8/1.8
950
46
3.4/1.6
46
3.5/1.7
46
3.7/1.7
46
3.8/1.8
ALTITUDE RANGE
FT. (M)
AVG. GAS
HEAT VALUE
(BTUH/CU
FT.)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
USA
4001 to
5000
(1219 to
1524)
750
43
3.3/1.6
43
3.4/1.6
43
3.5/1.7
43
3.6/1.7
775
44
3.6/1.7
43
3.2/1.5
43
3.3/1.6
43
3.4/1.6
800
44
3.3/1.6
44
3.4/1.6
44
3.6/1.7
43
3.2/1.5
825
45
3.8/1.8
44
3.2/1.5
44
3.4/1.6
44
3.5/1.6
850
46
3.8/1.8
45
3.7/1.8
45
3.8/1.8
44
3.3/1.6
875
46
3.5/1.7
46
3.7/1.7
46
3.8/1.8
45
3.7/1.8
900
47
3.8/1.8
46
3.5/1.7
46
3.6/1.7
46
3.7/1.8
925
47
3.6/1.7
47
3.7/1.8
47
3.8/1.8
46
3.5/1.7
* Orifice number 43 are factory installed
