44 march 2015 | FUEL OIL NEWS | www.fueloilnews.com
By GeorGe Lanthier*
Steam - Part 5
W
hen I discussed cutoffs previously in
January, I asked the following questions.
Did you find the answers?
1. What are the flow rates for most pipe
sizes that would be used on a fresh water (potable) feed
to a steam boiler, specifically ½" and ¾" pipe and at a
working pressure of 55-60 psi?
2. What is the average water content of a typical four
section steam boiler for oil (about 135,000 Btus? How
about the same boiler for gas?
The answer to the first question is that with a ½" pipe
you can flow about 10 gallons per minute and at ¾" you
can flow about 16 gpm, that's forced pressurized flow,
not heat transfer flow. The answer to the second question
is that a typical 4 section, residential, steam, oil boiler,
Figure 1, holds about 12 gallons of water to the "working
water line" and gas, steam boilers, Figure 2, hold about
9 gallons of water.
Now another couple of other questions? How long
will it take at 10 gpm to fill an empty boiler to the work-
ing water line? In either case you're talking, at full flow,
the ability to fill either boiler in about a minute and that's
from empty! How long does it take to put in a gallon or
two, well about 6 to 12 seconds, right?
So now we go back to the dilemmas. How do you fill
that boiler slowly and how do you protect the boiler from
HVAC/ HYDRONICS
Figure 2
Figure 1
Figure 3
Those 3/8" valves have a very definite
purpose, to control flow. you see a 3/8" pipe
only has a flow rate of 6 gpm at 55-60 psi,
but a ¼" pipe only has a flow of 3 gpm at the
same pressure.
