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Get Acrobat Reader You will need Acrobat Reader to view pdf CONQUEST® Flangeless Piping
Thermal Expansion & Expansion Loops

Like other piping materials, CONQUEST flangeless piping from Crane Resistoflex requires the designer or specifier to consider system movement caused by thermal expansion and contraction of piping components. This movement can typically be compensated for by using expansion loops and direction changes, along with the proper placement of piping supports and anchors.

You may find it necessary to conduct a computer-generated stress analysis of your piping system because of its size and complexity. Although most stress analysis programs simulate the movement of a single piping materials and plastic-lined piping is a composite of plastic and steel, use the coefficient of thermal expansion for steel in your stress analysis. That's because Crane Resistoflex Plastic-Lined Piping Products uses a swaging fabrication process for CONQUEST piping that locks the liner inside the steel shell and restricts its movement relative to the steel. The locking process distributes the liner's thermal expansion and contraction stress evenly throughout the entire steel pipe.

Coefficients of Thermal Expansion for Plastic Liners and Steel
Material α
(in/in/°F)
α
(mm/mm/°C)
Polypropylene (PP) 4.8 x 10-5 8.64 x 10-5
Polyvinylidene Fluoride
(PVDF Homopolymer)
6.6-8.0 x 10-5 11.9-14.4 x 10-5
PVDF/Hexafluoropropylene
(PVDF/HFP Copolymer)
7.8 x 10-5 14 x 10-5
Polytetrafluoroethylene (PTFE) 5.5 x 10-5 9.9 x 10-5
Perfluoroalkoxy (PFA) 7.8 x 10-5 14 x 10-5
Steel 5.9 x 10-6 10.6 x 10-6

How to Calculate Expansion Loop

Size and Dimensional Change - The expansion and contraction (ΔL) of a piping system is a function of the coefficient of thermal expansion for the piping material (α), the length of the pipe, and the upper and lower temperature limits of the system. These limits are the highest and lowest temperatures the system will experience at start-up, shut-down, and during operation.

Use Equation 1 to calculate the growth of shrinkage of pipe after a thermal cycle, where:

ΔL = Dimensional change due to thermal expansion or contraction (inches).
α = Expansion coefficient (in./in/°F or mm/mm/°C), refer to Table 1 for steel.
(T1 - T2) = Change in temperature (°F or °C).
L = Length (in inches or mm) of straight pipe being considered.

Equation 1:    L = α x (T1 - T2) x L
The minimum offset and loop size can be determined from the calculated dimensional change using Equation 1 & 2.

The loop size is a function of the pipe diameter and the length the pipe moves during a thermal cycle. See Equation 2. The expansion loop depicted in Figure 1 can be fabricated by using a combination of straight pipe, elbows, and/or MULTI-AXIS® precision-bent pipe.

To calculate loop size, use Equation 2 where:

R = Minimum expansion loop length (in feet or mm)
D = Actual outside diameter of the pipe (in inches or mm)
ΔL = Change in length (in inches or mm) due to expansion or contraction

Equation 2:   R = 6.35 x (D x ΔL)1/2
(Metric)         R = 76.4 x (D x ΔL)1/2

Example: To determine how much expansion and contraction will occur in a 530-foot straight length of 2" PVDF-lined pipe and how long the expansion loop will have to be to compensate for this, you must first determine the highest and lowest temperatures the system will experience. Assume the pipe will be installed at 60°F, operated at 75°F, and experience temperatures of 0°F in winter and 120°F in summer.

With this information, use Equation 1 to determine the dimensional change of the straight pipe section.

ΔL = 5.9 x 10-6 x (120-0) x 530 x 12 = 4.5 inches

The change in length of the straight pipe section due to expansion is 4.5 inches. Substituting 4.5 inches for ΔL in Equation 2, determines the loop size to compensate for this expansion.

R = 6.35 x (2.375 x 4.50)1/2 = 20.8 ft.

Therefore, the minimum expansion length offset or direction change is 20.8 feet.


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