8
2.0 INFORMATION TO STEAM FITTER
Assuming availability of 30 psi supply steam pressure immediately to the appliance, then
pipe sizes of ½" or 3/4" or 1" will deliver respectively 90, 165 or 385 lbs. of steam per
hour to the appliance Heat Exchanger. From the foregoing to use ½" pipe line would
most likely prove inadequate.
An extremely important consideration is the pressure drop that will occur through the
steam supply line from its point of origin to the appliance. The greater the length of
piping and number of valves and elbows, the greater will be the pressure losses.
Consider a pressure drop of 1 (one) psi for each straight length of pipe equivalent to 120
diameters of that pipe. Thus, a 1" pipe having a straight length of 120" (10 feet) is
equivalent to 120 diameters of that pipe and will have a pressure loss of 1 psi through
that pipe.
Example:
1. Note, in 3/4" pipe size, that a Standard 90º Elbow and Angle Valve and a Globe
Valve are equivalent to 1.8 feet, 10 feet and 18 feet respectively of straight pipe.
Similarly, in a 1" pipe size, a standard 90º Elbow and Angle Valve and a Globe Valve
are equivalent to 2.2 feet, 12 feet and 23 feet respectively of straight pipe.
Example:
Total of above = 20 + 2.2 + 3 + 2.2 + 17 + 23 + 10 + 2.2 = 79.6 feet. Since each 10
feet is equivalent to 1 psi pressure loss, 79.6 feet is equivalent to approximately 32
psi from an original Boiler supply of 40 psi.
9 p.s.i.
Available
Pressure
10 p.s.i.
Supply
Pressure
120 Diameters of 1” pipe
Equivalent to 120” (10 ft)
20’
32 PSI
3’
90° ELBOW
17’
10’
GLOBE VALVE
1” PIPE
40 PSI
SUPPLY
