Burnham SCG manual Gas Piping, Gravity Factor

V. Gas Piping

WARNING

4. Specific gravity of gas. Gas piping systems for

gas with a specific gravity of 0.70 or less can be

sized directly from Table 7, unless authority having

Failure to properly pipe gas supply to

jurisdiction specifies a gravity factor be applied.

boiler may result in improper operation and

For specific gravity greater than 0.70, apply gravity

damage to the boiler or structure. Always

factor from Table 6. If exact specific gravity is not

assure gas piping is absolutely leak free

shown choose next higher value.

and of the proper size and type for the

connected load.

Table 6: Specific Gravity Correction Factors

An additional gas pressure regulator may

be needed. Consult gas supplier.

Specific

Correction

Specific

Correction

A. Size gas piping. Design system to provide adequate gas

Gravity

Factor

Gravity

Factor

----

----

0.85

0.81

supply to boiler. Consider these factors:

1. Allowable pressure drop from point of delivery to

----

----

0.90

0.82

boiler. Maximum allowable system pressure is ½

0.60

1.00

1.00

0.78

psig. Actual point of delivery pressure may be less;

0.65

0.96

1.10

0.74

contact gas supplier for additional information.

Minimum gas valve inlet pressure is stamped on

0.70

0.93

1.20

0.71

the rating label located in the boiler’s vestibule

0.75

0.90

1.30

0.68

compartment.

2. Maximum gas demand. Refer to the boiler’s input

0.80

0.87

1.40

0.66

as printed on it’s rating label. Also consider existing

and expected future gas utilization equipment (i.e.

For materials or conditions other than those listed

water heater, cooking equipment).

above, refer to National Fuel Gas Code, NFPA54/ANSI

3. Length of piping and number of fittings. Refer to

Z223.1, or size system using standard engineering

Table 7 for maximum capacity of Schedule 40 pipe.

methods acceptable to authority having jurisdiction.

Table 8 lists equivalent pipe length for standard

fittings.

Table 5: Gas Ratings

Boiler

Natural/LP

Minimum Natural

Minimum LP

Natural

LP

Maximum

Gas Pressure

Gas Pressure

Manifold

Manifold

Model

Gas Pressure

(in. w.c.)

(in. w.c.)

Pressure

Pressure

Number

(in. w.c.)

Inlet to Gas Valve

Inlet to Gas Valve

(in. w.c.)

(in. w.c.)

SCG-3

SCG-4

SCG-5

SCG-6

14

4.5

11.5

3.5

10.5

SCG-7

SCG-8

SCG-9

NOTICE

SCG boilers built for altitudes greater than 4,999 feet above sea level need to be specially orificed to adjust for changes in atmospheric conditiions. The SCG boiler "H" Model has been certified to operate in atmospheric conditions from 5,000 to 10,000 feet above sea level. Input is derated by 10% for applications at 5,000 feet above sea level, and 20% for applications at 10,000 feet above sea levels. Derate is based on 2% reduction per 1000 feet.

The SCG boiler is available in two (2) altitude Models: The "S" Model 0-4,999 feet above sea level, and the "H" Model 5,000-10,000 feet above sea level.

For applications above 10,000 feet, consult the manufacturer.

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