Page 234 - Boiler plant and distribution system optimization manual
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Boiler Plant Calculations 219
STEAM LEAK RELIEF VALVE 1,165 lb/hr x 837 Btu/lb = 975,000 Btu/hr
(Ans .: $8 .00 x 0 .975 MBtu/hr = $7 .80/h,($187 .20/
A relief valve on a low pressure, 30 psig, day) ($5,616.00/mo) ($67,392.00/yr)
header has started to blow steam. An examina-
tion of the make-up water readings indicates an 4. The condensate temperature drops from
increase of 28,776 gallons per day starting when 200F to 155F returning to the boiler plant,
the relief valve began blowing steam. how much is this costing?
Fuel is distillate no. 2 costing Average condensate return 100,000 lb/hr
$4.50 per million Btus
City water 50F Heat loss 45 Btu/hr
18 Btu/lb
Fuel Btus needed to make 30 psig steam with Replace heat with 80%
a boiler efficiency of 80% efficient boiler 56 Btu/lb
(1172 – 18)/.80 = 1443 Btu/lb)
(Ans .: 56 Btu/lb x $8 .00 MBtu x
1. How many pounds of steam is escaping from 100,000 lb/hr = $44 .80/hl
the steam system a day? ($1,075.20/day) ($32,256/mo) ($387,072/yr)
28,776 gallons/day x 8.34lb/gal =
240,000 lb/day
Condensate Losses $387,072/yr
2. How much is this costing in fuel dollars? Steam Pipe losses $ 67,392/yr
——————
240,000 lb. x 1443 Btu/lb = $454,464/yr
346 MBtus/day
346 x $4.50 = $1,557/day
ELECTRICAL LOSSES
DISTRIBUTION SYSTEM INSULATION LOSSES The purpose of this section is to show how
electrical losses play a pmt in the overall energy
Situation: You are investigating putting a new consumption of a boiler plant. Operating electri-
boiler in a building 2,500 ft from the boiler plant cal equipment, especially if it is oversized for the
to cut losses. You need to know how much money load on the plant can add to unnecessary plant
you can save by eliminating the 2,500 ft of6,” 250 losses. The examples in this section are based on
psi steam piping and 2” condensate piping. nameplate data, field measurements of electrical
loads should be taken to confirm actual condi-
1. How would you find out how much heat is tions.
being lost in the steam piping?
(Ans .: You weigh the water formed in its steam Example 1. You find a grossly oversized 40 hp
traps and collect 1,165 pounds an hour.) blower in your plant. A 5 hp could do the same
job how much money could be saved by changing
2. How much energy was given up by the out the 40 hp unit?
steam to form this water? With a cost for electrical power of 10 cents
(Ans .: The latent heat of 250 psi steam is 837 per kilowatt hour, what will the difference in cost
Btu/lb.) be to run with the smaller blower?
3. Steam costs $8.00/MBtus, how much is the A. How much does it cost to operate the 40 hp
steam piping insulation losses costing? blower per hour? (Ans.: $3.50/hr)
