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TRANSCRIPT
Designing Systems
toCompensate
forThermal
Expansionand
Contraction
Things We Have Learned From Being Sued
6” Model MC - 6 CorrugationsAnchor Load @ 150psi - 11,600#
This is why you should use guides
Riser F3 Floor 4‐25 Room 2‐4
Use Any Natural Flexibility In The piping layout
2008 ASHRAE Handbook
Heating, Ventilating, and Air Conditioning Systems and Equipment
Chapter 45
Or this can be simplified to
L = 6.225 √ΔD
L = 3ΔDE√(144in²/ft²)SA
Where Δ = Thermal expansion of leg ABD = Pipe Outside DiameterE = Modulus of ElasticitySA = Allowable Stress
For a Basic Expansion ElbowHard Pipe Δ
L
Anchor
Anchor
A
B
C
L = 4 √ΔD Where Δ = Thermal expansion of leg ABD = Pipe Outside DiameterE = Modulus of ElasticitySA = Allowable Stress
For a Basic Expansion “Z” Bend Hard Pipe
X
X
Guide
Guide
AnchorAnchor
L
L
L
A
B
Anchor to Anchor Expansion
So what kind of expansion joint to use?
L = 6.225 √ΔD
W = L/5H = 2*W
Where Δ = Thermal expansion of runD = Pipe Outside DiameterE = Modulus of ElasticitySA = Allowable Stress
For a Basic Expansion Loop Hard Pipe
XX
AnchorAnchor
Guide
Guide
Anchor to Anchor Expansion
2H 2H
W
H
Hard Loops Pro/Con
Same material as the rest of piping
Constructed on site, costly to fabricate, hang and insulate
Grandfather used ‘em
Medium anchor loads
Constructed on site
Pro
Needs lots of room
High lateral loads on moment guides.
Con
Flexible Expansion Loop
“V” Loops
The flexible pipe loop is also smaller and has less anchor load than a hard pipe loop
Hose Basics
Corrugated stainless steel hose by itself
has great hoop strength, but poor tensile
strength
Virtually any amount of movement
Cap weld,
welding the
hose, braid and
collar together
Weld the End Fitting to the Hose
On a flex loop the braid is the anchor
X
X
165
Feet
2.85
”Exp
.
50 Feet
.59” Exp.
19 F
eet
19 Feet
Guides
4” Sch 40 Carbon Steel With Hard Pipe Expansion 90
Anchor with 582 pounds force
X
X
165
Feet
2.85
”Exp
.50 Feet
.59” Exp.
3 Fe
et3 Feet
Guides
4” Sch 40 Carbon Steel With H&B Dog Leg
Anchor with 180 pounds force
Hose & Braid
Flexible Loop Pro/Con
Very compact Some pressure limitations
No maintenance
Minimal guiding requirements
Lowest anchor loads, almost no structural considerations.
Least expensive optionStandard or custom fit
Large movement
Seismic capable
Pro Con
• Axial movement• Lateral movement• Angular movement
There’s a lot of choices of Bellows
Axial Bellows Externally Pressurized Axial Bellows
Untied Double Bellows Gimbal Bellows
Dual Tied BellowsDouble Hinged
BellowsSingle Hinge
Bellows
Internally Pressurized
Externally Pressurized
Axial movement onlyCapable of Axial, Lateral and
Angular movements.
Expansion
Compensators
externally
pressurized
Atmosphere
Built in Liner
Squirm- Strut Instability - Limits the movement of internally pressurized bellows
The balance between the number of convolutions needed for the movement exceeds the stability of the bellows
Internally Pressurized Bellows
Axial
Are Primarily Designed to Handle
Axial Movement
On the other hand,a dual-tied bellows moves
And laterally
Axially
Dual-tied bellows joint
Anchors
• Pressure ThrustPressure X effective area ( Use test pressure if greater )
Calculating forces on anchors
•Deflection Load –Published Spring Rate X movement of the joint
• Frictional ResistanceTotal weight of pipe, media, insulation & equip. X coefficient
• Pressure ThrustPressure X effective area ( Use test pressure if greater )
• Example:4”= 35.96 sq. in effective area x 125 PSI = 4495 #.
Calculating forces on anchors
To calculate the thrust load:Effective Areas
Pressure Thrust for the Model MC Ring Controlled Self-Equalizing
Expansion Joint The average car weighs only
3000#
Deflection Load (spring rate)
Totally independent of pressure or temperature
• Published Spring Rate X Actual movement of the joint
• Example:4” with 6” Axial = Spring rate of 143 lbs/in
X4.3 (total amount of expansion)
= 614.9 lbs
Deflection Load on Anchors
•Frictional ResistanceTotal weight of pipe, media, insulation & equip. X coeff.
•Example4” sch. 40 pipe at 10.8 #/ft x 75 ft = 1890 #
4” pipe internal area 12.73 sq.in. / 144 in. per sq.ft. = 0.088 cu.ft. x 175 linear ft. = 15.4 cu.ft. total volume
125 PSI steam = 3.23 cu.ft. per pound = 4.76# weightadd guides & joint & insulation at 500#
Total 2395# x 0.3 Coeff. = 719# frictional resistance
Calculating forces on anchors
Total Anchor Force
4495 Pressure Thrust614 Deflection Load719 Friction Resistance5,828.9 lbs force
The engineer may add other loads such as snow, ice, wind, based on project conditions
Intermediate AnchorsIntermediate anchors between expansion devices do not see the full load.
X
Intermediate Anchor
MainAnchor
X X
MainAnchor
Expansion Joint
EJMA recommends to design intermediate anchors for the spring load of one of the joints
X
MainAnchor
X
X
Expansion Joint
Anchors at fittings can have multi-directional loads
Force
Force
Expansion Joint
Location
Makes a Difference
Guiding
Column strength of pipe.
Total Anchor Force
4495 Pressure Thrust614 Deflection Load719 Friction Resistance5,828.9 lbs force
Remember our Example
LINERS•When velocity is high and could set up vibration in bellows
•Compressed air lines
•Exhaust gases
•Abrasive flow media
•Rule of Thumb :When velocity > 10 FPS
Install 1st. Guide a max. of 4 pipe dia. From the expansion joint.Install 2nd. Guide a max. of 14 pipe dia. From the 1st. Guide. Additional guides as per EJMA recommendations
Bellows Pro/Con
Low/ no pressure drop High anchor loads
Externally pressurized-large movement
Easy to insulate
Custom fit
No maintenance
Very compact Engineered anchors
Considerable guiding requirements
Pro Con
Torque can be a problem
Slip type Joints
Slip Type Joint
Slip Joint construction detail
Ball Joints
Always in, at least pairs
Similar construction with Slip joints
Same maintenance issues
Slip Type Pro/Con
Low/ no pressure drop High anchor loads
Custom fit
Large movementVery compact
Very expensive
Low or no cycling is a detriment.
Very High maintenance –packing frequently needed
Crucial and Considerable guiding requirements
Engineered anchors
Pro Con
12”8”
6”
250’ 75’
85’ 75’
150’
150’
75’
Lets Start With Determining The Pipe Size and Pipe Dimensions
To Calculate Expansion
1 Determine design temperature – for example 200° F.
2 Establish installation temperature - For example 50° F
3 Find the expansion rate per 100 feet –1.179” / 100 feet for steel – 1.728” / 100 feet for copper
4 Determine the length of pipe run – for example 165 feet
5 Multiply the expansion rate by the length.(165 / 100) X 1.179 = 1.94” Expansion
6 If the joint is for both thermal and seismic, the values must be added together!
For An Example
Lets use
Pipe Material Carbon SteelService Hot WaterDesign Temperature 200°FInstallation Temperature 50° FTemperature Difference ΔT 150°FExpansion Rate ΔL 1.179 inches / 100 Feet
12”8”
6”
250’ 75’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.88”
0.88”
Lets Calculate How Much The Pipe Will Expand
12”8”
6”
250’ 75’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.88”
0.88”
Lets Establish The Anchor Points
X
X X
X
XX
Anchor(typ)
Anchor(typ)
First check for Natural
Flexibility
First check for Natural
Flexibility
Keep in Mind
90° changes in direction are the most efficient piping configuration to use to take up thermal expansion or contraction.
Smaller angles will compound the movements!
12”8”
6”
250’ 75’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.88”
0.88”
Next, Use Any Natural Flexibility Of The System
X
X X
X
XX
Anchor(typ)
Anchor(typ)
22’
13’
12”8”
6”
250’ 75’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.88”
0.88”
Next, Complete The System WithFlexible Pipe Loops
X
X X
X
XX
Anchor(typ)
Anchor(typ)
22’
13’MLW81200
MLW80800
MLW30600
12”8”
6”
250’ 75’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.88”
0.88”
X
X X
X
XX
Anchor(typ)
Anchor(typ)
22’
13’
Or, Complete The System WithExpansion Joints
Don’t forget about the guides. Note the placementof the Metragators
12”8”
6”
250’ 75’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.88”
0.88”
What if the 75 foot run was only 18 feet?
X
X X
X
XX
Anchor(typ)
Anchor(typ)
22’
13’
12”8”
6”
250’ 18’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.21”
0.88”
Option 1Use a Hose & Braid Dog Leg
X
X X
X
XX
Anchor(typ)
Anchor(typ)
40”
13’
12”8”
6”
250’ 18’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.21”
0.88”
Option 2Add an Anchor, and another expansion device
X
X X
X
XX
Anchor(typ)
Anchor(typ)
18’
13’
X
12”8”
6”
250’ 18’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.21”
0.88”
Next, Complete The System WithFlexible Pipe Loops
X
X X
X
XX
Anchor(typ)
Anchor(typ)
18’
13’MLW81200
MLW80800
MLW30600
X
MLW30800
12”8”
6”
250’ 18’
85’ 75’
150’
150’
75’
2.95”
1.0”
1.77
”1.
77”
0.88
”
0.21”
0.88”
Or with Expansion Joints
X
X X
X
XX
Anchor(typ)
Anchor(typ)
22’
13’
X
