PVC Pipes - Expansion Loops
Temperature expansion and contraction in PVC piping systems
Temperature expansion and contraction in PVC piping systems can be compensated with
- expansion loops consisting of pipes and 90o elbows
- flexible bends
- bellows and rubber expansion joints
- piston type expansion joints
Expansion Loops
Expansion loops are made of standard pipes and elbows and can be produced on the site and adapted to the actual situation.
The length of leg A can be calculated as
A = 0.72 (D δl)1/2 (1)
where
A = length of leg A (ft)
D = nominal outside diameter (inches)
δl = thermal expansion of pipe (inches)
The length of leg B can be calculated as
B = 1.44 (D δl)1/2 (2)
where
B = length of leg B (ft)
Example - Expansion Loop
A 2" PVC Schedule 40 straight pipe with length 300 ft is installed at 75oF and operated at 120oF. The expansion coefficient of PVC is 28 10-6 in/in oF.
The expansion of the PVC pipe can be calculated as
δl = α Lo δt
= (28 10-6 in/in oF) (300 ft) (12 in/ft) ((120 oF) - (75 oF))
= 4.5 inches
where
δl = expansion (inch)
Lo = length of pipe (inch)
δt = temperature difference (oF)
α = linear expansion coefficient (inch/inch oF)
The length of leg A can be calculated:
A = 0.72 (D δl)1/2
= 0.72 [(2.375 in) (4.5 in)]1/2
= 2.4 ft
The length of leg B can be calculated:
B = 1.44 (D δl)1/2
= 1.44 [(2.375 in) (4.5 in)]1/2
= 4.7 ft
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