Steam Basics
©2008 Armstrong International, Inc.
Steam Basics - Overview
• What is Steam?
• Why is Steam Used?
• How Do We Create Steam?
• How Do We Identify Steam Properties?
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This Is Not Steam!
• Steam is a vapor
form of water, and
is colorless,
tasteless, and
odorless
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What is Steam Used For?
Steam is Used to Transfer Heat
Energy From One Location to
Another
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Why Use Steam
We have already
developed the
equipment and
expertise to design
and install steam
systems for many
different
applications
We have a lot of
knowledge
concerning
steam
Steam is an
efficient heat
transfer
medium
Steam is
easily
controlled
How We Create Steam
• Steam is created by adding Heat Energy to water.
• Heat Energy is expressed in Btu’s.
• 1 Btu is the amount of Heat Energy required to
raise the temperature of 1 pound of water by 1F.
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How We Create Steam
The Heat Energy required to create steam has two
forms:
Sensible Heat
Latent Heat
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Heat Energy – Sensible Heat
• Sensible Heat is the amount of Heat Energy
required to raise the temperature of water from
32°F to the boiling point (saturated liquid) at a given
pressure
– Sensible Heat raises the temperature of the water and
can be sensed with a thermometer
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Heat Energy – Sensible Heat
O PSIG
212 F.
1 lb. Water
HEAT
1 Lb. of Saturated Water at
Atmospheric Pressure Contains
180 Btu’s of Sensible Heat
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Adding Heat Energy – Sensible Heat
250 F.
15 PSIG
1 Lb. of Saturated Water at
15 PSIG Contains
218 Btu’s of Sensible Heat
HEAT
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Heat Energy – Sensible Heat
308 F.
60 PSIG
1 Lb. of Saturated Water at
60 PSIG Contains
277 Btu’s of Sensible Heat
HEAT
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Heat Energy – Latent Heat
• Latent Heat is the amount of Heat Energy required
to transform water at the boiling point (saturated
liquid) to steam
– Adding Latent Heat does not raise the temperature –
saturated liquid and steam have the same temperature
for a given pressure
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Adding Heat Energy – Latent Heat
O PSIG
212 F.
1 lb. Steam
HEAT
1 Lb. of Steam at Atmospheric
Pressure Contains
970 Btu’s of Latent Heat
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Adding Heat Energy – Latent Heat
250 F.
15 PSIG
HEAT
1 Lb. of Steam at 15 PSIG
Contains 945 Btu’s of
Latent Heat
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Adding Heat Energy – Latent Heat
308 F.
60 PSIG
1 Lb. of Steam at 60 PSIG
Contains 904 Btu’s of
Latent Heat
HEAT
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What is the Effect of Pressure?
Increased Pressure:
– Decreases the amount of Latent Heat
– Increases the amount of Sensible Heat
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What is the Effect of Pressure?
1000
900
800
700
600
500
400
300
200
100
0
0 psig
15 pig
50 psig
Latent
Heat
BTU/lb
Sensible
Heat
BTU/lb
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What Is The Effect Of Pressure?
• Increased Pressure:
– Decreases the Specific Volume
Spe cific Volume v s. Pre ssure
(cu. ft / lb)
30
(psig)
26.8
0 PSIG
25
15 PSIG
20
13.8
60PSIG
15
10
5.8
5
0
1
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What Is The Effect Of Pressure?
• Increased Pressure:
– Increases the Steam Temperature
Steam Temperature vs. Pressure
(psig)
(Deg. F)
400
300
0 PSIG
308
250
212
15 PSIG
60PSIG
200
100
0
1
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Specific Volume
Latent Heat
Sensible Heat
Steam Pressure
The Pressure / Temperature /
Volume Relationship
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Identifying Steam Properties
Steam Tables
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Steam tables allow us to
identify all of the important
properties of steam, given
either the steam temperature or
the steam pressure
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Example: Steam at 250oF is at 15 psig, with 945 Btu’s/lb of Latent Heat
Steam at 5 psig is at 228oF, with 196 Btu’s/lb of Sensible Heat
Now That We’ve Made Steam
What Do We Do With It
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Since Steam is used to Transfer
Heat Energy From One Location
to Another . . .
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It only makes sense that we take
the heat energy back out and
use it to do work.
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Removing Latent Heat
1 lb. of Steam at 212F, with a TOTAL HEAT content
of 1150 Btu/lb. – 970 Btu’s of LATENT HEAT
= 1 lb. of boiling water (Saturated Liquid) at 212F
with a heat content of 180 BTU’s/lb.
1200
1000
Btu's
970
1150
800
600
400
180 212
200 32
0
212
Atmospheric Pressure
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Remember:
The Latent Heat added at the boiler is what we have
available to do work in our equipment
BUT . . .
When we remove Latent Heat we create Condensate
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Latent Heat can be removed
intentionally, in a piece of heat
exchange equipment, or
unintentionally, from radiation
heat loss in piping
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What does this Unintentional Heat
Loss Mean to your Steam System?
Condensate
Steam
Vapor
50.3 psig
297.97F
100 psig
337.9F
PRV
Trap
Trap
Trap
Trap
Trap
Trap
Vent
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It Means:
The Steam System is Constantly Being Filled With
Water (Condensate)
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It Means:
Your Steam System is Subject to Corrosion
( CO2 + H2O = H2CO3 )
Subcooled Condensate + CO2
Forms Carbonic Acid
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It Means:
Your Steam System is Subject to Water
Hammer
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It Means:
Your Heat Exchange Equipment is
Less Efficient
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It Means:
Your System Must Be Properly Piped
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It Means:
Your Equipment Must Be Properly Trapped
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Armstrong Promise
We provide intelligent system solutions that improve
utility performance, lower energy consumption, and
reduce environmental emissions . . . while providing
an “enjoyable experience”!
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©2008 Armstrong International, Inc.