In Memoriam:
Steve Clark
President & CEO, Aquatherm
November 1, 1957 – May 24, 2013
THERMAL EXPANSION
IN PIPING SYSTEMS
New Solutions to an age old
Engineering Challenge
Steve Clark, P.E., C.E.M.
President & CEO
Aquatherm
THERMAL EXPANSION
a = Thermal Expansion Coefficient
Steel -- 1”/100 oF/100 FT
Copper – 1.5”/100 oF/100 FT
Plastics - 10”/100 oF/100 FT
L = Straight length of pipe
dT = Max operating Temp – Installed Temp
THERMAL EXPANSION FORCE
• F = AE a (T2–T1)
• Notice that the initial length and change in length
do not matter in calculating the stresses and
forces.
• A = Cross section of pipe in
• E = Young Modulus
• Steel 27.5 x 106 lbf /in2
• Polypropylene .29 x 106 lbf /in2
• a = Coefficient of Linear Expansion
THERMAL EXPANSION STRESS
• Steel – 19,148 lb/in2 Irresistible
force
• Polypropylene – 2,518 lb/in2
Manageable force
A LITTLE INTERNAL RESTRAINT
• Fiber strips in bedded middle layer
running parallel with the axial force
• Resist Thermal Expansion
• Reduce expansion from 10
inches per 100’ per 100 F
to 2.3 inches per 100’ per
100 F
• Also increase the R-value
of the pipe wall from 1 to
1.4 per inch
WHY ENGINEERED PP-R SYSTEMS?
The Right Features
Faser-composite Layer
Innovative fiber
core layer reduces
thermal linear
expansion by 75%
(comparable to copper expansion)
Faser-composite PPR vs. Regular PPR
THERMAL EXPANSION STRESS
• Steel – 19,148 lb/in2 – Irresistible force
• Polypropylene – 2,518 lb/in2 Manageable
force
• Polypropylene with fiber – 630 lb/in2 Minor
force
A LITTLE EXTERNAL RESTRAINT
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For buried pipe, the frictional force
Eq. 1: F = ApC ƒ c + LpWtan(ƒØ Ø)
Where: Ap = , ft2 ; area of pipe surface bearing against the soil
C = Cohesion of the soil, lb/ft2
ƒ c = proportionality constant based on shear tests of surface to soil
interface
Lp = Length of pipe, ft.
ODp = Outside diameter of pipe, ft.
W = 2We + Wp + Ww , lb/ft.; normal force per unit length
We = Vertical load on top and bottom surfaces (prism load), lb/ft
Wp = Weight of pipe, lb/ft
Ww = weight of water in pipe, lb/ft
RESTRAINED BY THE SOIL
Using this worst-case soil (silty sand)
loading for a section of Aquatherm SDR 7.4
PP-R piping results in a frictional force of
5,634 lbf at a burial depth of 1 ft. This is well
above the axial force imposed by the
thermal expansion (4,800 lbf ) and will
readily restrain the pipe from movement.
Note that at a burial depth of 3 ft., this
frictional force increases to 16,350 lbf over
this same section of piping.
ELIMINATING THERMAL
EXPANSION LOOPS
• Saves Installation costs - Pipe, fittings, labor,
space
• Energy Savings–Increase Pressure Drop
• Maintenance Cost Savings
• Fusion connections make thrust blocking
unnessary
• 5 to 40 % more
pressure drop
• More heat loss
ADDITIONAL DISTRIBUTION SAVING
OPPORTUNITIES
• Reduce heating supply temperature, but
keep high delta T
– Reduces thermal expansion and stresses
– Reduces heat loss
– Energy Source options
• Higher efficiencies
• More flexibility in Energy Sources
Heat pumps, solar, waste heat,…
ADDITIONAL DISTRIBUTION SAVING
OPPORTUNITIES
• Use Natural Insulation
– Dry Sand
– R- value is .3 to .7 per inch
– 10 inches sand replaces 1 to 1.5 inches of
insulation
CHILLED WATER DISTRIBUTION SAVING
OPPORTUNITIES
• Raise Chilled Water Return temperature, high delta T
– Reduces thermal expansion and stresses
– Reduces heat gains
– Energy Source options
• Higher efficiencies
• More flexibility in Energy Sources
Heat pumps, geothermal, thermal storage,…
• Use Natural Insulation
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Dry Sand
R- value is .3 to .7 per inch
10 inches sand replaces 1 to 1.5 inches of insulation
Drainage, do not trap moisture against pipe
TRENCH DESIGN
CLEAN ENERGY OPTIONS
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Co-generation
Tri-generation
Solar thermal
Geothermal
Ground or ground water
source heating and cooling
Waste energy recovery
Fuel switching
Bio-fuels
High efficiency chillers
Direct cooling from tower
cooling
Thermal storage
Time of day rates
HVAC SYSTEMS EUROPEAN TRENDS
• Hydronics
– Moving thermal energy with air takes 10 times more energy
than with water.
• Radiant heat – Low temp heat source
– Lower room temperature
– Low auxiliary energy
• Radiant cooling – Warmer cooling source 55° F
– Warmer room temp
– Low auxiliary energy
– In Germany over 60% of new construction uses radiant cooling
OVERCOMING ROADBLOCKS FACING
THERMAL DISTRIBUTION
• Campus disruption
• First cost
• Maintenance cost
AVOIDING CAMPUS DISRUPTION
• The future is boring…
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Directional (horizontal) boring and pulling the pipe
Fusing pipe together before pulling
Avoids trenching and ripping up surface
Go under parking lots or tennis courts, trees, etc..
REDUCING FIRST COST
• Horizontal pipe pulling
• Eliminate insulation
• Insulation systems can cost more then the
pipe
• IECC and ASHRAE have added an exception
for Buried Chilled Water Pipe Insulation
• Eliminate thrust blocking
• Eliminate expansion loops
REDUCING MAINTENANCE COSTS
• Eliminate Leaks
– From Joints
• Fusion connections
• No leak path
• Strongest part of System
– From Pipe
• Right material
• Compatible with water
• Compatible with all common chemicals
THERMAL FUSION JOINTS
• Two pieces heat and become one
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Socket fusion
Butt welding
Electro-fusion
Outlet fusion
THE RIGHT CONNECTION:
HEAT FUSION (WELDED)
• Perfectly bonded connection
(stronger than the pipe)
• Labor saving
• No glues, gaskets, solders or crimps
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Most socket connections in
under 2 min
No dangerous chemicals or open
flames
No FM burn permits required
BUTT WELDING
LARGE PIPE
• Face pipe ends flat
• Heat pipe ends
• Hold together under
pressure
MINIMIZES LIABILITY
• No leaks
– No weak links at fittings
– No gaskets
– No bad crimps
– No working its way loose
– Abrasion resistant
– Chemical resistant
– 10 year warranty
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Covers parts, labor, and water damage
METAL AND WATER DON’T MIX
WHY PP-R SYSTEMS?
• Polypropylene-Random
– produced using a by product of refining process
• Sustainable
– 50 – 60 year service life rating for most systems
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Recyclable
LEED friendly
Non-toxic
Energy saving
– Low Pressure Drop / Low Heat Loss
Eliminates: Corrosion,
Abrasion, Leaching,
Toxins, Leaks
INSULATION OPTIONS
• Insulating Chilled Water Lines unnecessary
• Not required under ASHREA 90.1 or IECC 2012
• Does not pay back
• Insulating Hot Water lines may be done
using sand
• Saves first cost
• About R=.5 per inch
UNIVERSITY OF SOUTHERN
MISSISSIPPI
• $10 million Science Building
• USMGP Physical Plant
• 7 years old – energy efficient
• district energy plan – had
sufficient capacity
• Located approximately 2,000 feet
away
USM – CHILLED WATER
DISTRIBUTION OBSTACLES
• Campus Icon: The Friendship Oak.
• 500 years old
• On The Beach - salt-laden environment
USM – CHILLED WATER
DISTRIBUTION FEEDBACK
• Trench through open field
• Directional Boring under
Tennis Courts, Campus
thoroughfare, building and
The Friendship Oak.
SUMMARY
• District Energy Systems
are the best answer to our
energy dilemma.
• Medium-temperature fluid
thermal distribution
systems offer the most
advantages for District
Energy.
• Technologies like
eliminating expansion
loops, horizontal boring,
heat fusion, and
engineered polypropylene
pipe make it better than
ever!
In Memoriam:
Steve Clark
President & CEO, Aquatherm
November 1, 1957 – May 24, 2013