PVC Pipes - Expansion Loops

Temperature expansion and contraction in PVC piping systems

Temperature expansion and contraction in PVC piping systems can be compensated through

• expansion loops consisting of pipes and 90^o 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 adapted to the actual situation.

The length of leg A can be calculated by formula

A = 0.72 (D δl)^1/2         (1)

where

A = length of leg (ft)

D = nominal outside diameter (inches)

δl = thermal expansion of pipe (inches)

The length of leg B can be calculated by formula

B = 1.44 (D δl)^1/2        (2)

where

B = length of leg (ft)

Example - Expansion Loop

A length of 300 ft straight pipe of 2" diameter PVC Schedule 40 is installed at 75^oF and operating at 120^oF. The expansion coefficient of PVC is set to 28 10^-6 in./in^oF.

The expansion can be calculated as

δl = α L_o δt

    = (28 10^-6 in/in ^oF) (300 ft) (12 in/ft) ((120 ^oF) - (75 ^oF))

    = 4.5 inches

where

δl = expansion (inch)

L_o = length of pipe (inch)

δt = temperature difference (^oF)

α = linear expansion coefficient (in./in.^oF)

The length of leg A can be calculated as:

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 as:

B = 1.44 (D δl)^1/2

    = 1.44 [(2.375 in) (4.5 in)]^1/2

    = 4.7 ft

• The Expansion Loop calculation as Excel file

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