Page 126 - PRESS-FIT SYSTEMS FOR DIVERSE APPLICATIONS

3.0 TECHNICAL DATA
SYSTEM DESIGN CONSIDERATIONS

AND TUBE EXPANSION

CALCULATION OF THE EXPANSION COMPENSATION ∆L ∆L
LENGTH 2 2
Bd
In case of greater expansion, expansion compensators or, in ∆L
complicated cases Ω-shaped compensating loops will need to Bd Lb Lb
be fitted and calculated. The formula with which the expansion ∆L 2
equaliser in mm is calculated is as follows:
B = k x √(d x ∆l) ∆L
d
e
= expansion compensation length (mm) (Figure 12) (Figure 13) (Figure 14)
B d
k = material constant
The nomogram in graph 1 enables the fast and accurate
45 for XPress Stainless and Carbon tube, establishment of the expansion bend length (B ) considering the
d
35 for copper tubes respective tube types and the expansion to be compensated
(∆). Graph 2 shows the values (L b) for the installation situation
d e = outside diameter of the tube (mm)
illustrated in figure 14.
∆l = linear expansion that needs to be The following is an example of an analytical calculation: A tube
compensated (mm)
network with a length of 16m consisting of XPress Stainless tubing
with a diameter of 22mm subject to a temperature difference of
Nomogram for calculating the Z and T expansion equaliser for stainless steel 60 K. When using the equation for calculating the expansion, the
Minimum length ( B d ) of the expansion equaliser (mm) Without the requirement for the mathematical calculation, we
result is:
∆l = 16 x 0.0166 x 60 = 15.936
would get the same result through interpolation of the data
in table 20. With the expansion for the respective section of
the pipeline, we need to calculate the length of the expansion
compensator required for its compensation - see figures 12 and 13.
Using the nomogram in graph 1, we get ca. 830mm. The analytical
calculation shows:

In case of an Ω-shaped expansion connection, the calculated
value of the expansion equaliser also visible from figure 14 is to be
Length change ( ∆l ) in mm B d = 45 x √(22 x 15.936) = 827.2 mm
Graph 1: Nomogram (for XPress Stainless) for calculating the halved as it is actually two expansion sections. The value (B ) is not
d
situation fig. 12 and 13. Expansion B (mm) exactly divided by two, but should be divided by a factor of 1.8:
d
L = 25 x √(22 x 15.936) = 468.1 mm
b
Nomogram for calculating the Ω expansion equaliser or otherwise: b
Minimum length ( B d ) of the expansion equaliser (mm) As can be seen in figures 12-14, a correct compensation of the
L = B / 1.8 = 842.58 / 1.8 = 468.1 mm
b
d
Graph 2 shows a value for L of ca. 468mm.
expansion depends also on the placement of fixing devices
such as saddles and clips. Never plan for or place tube saddles
as a mounting device close to a tube connection. Clips should
be positioned such that they do not behave as a fixed restraint.
When there are straight segments of tube, without expansion
compensation, use only one saddle to prevent possible
segment as possible: in this way, any expansion will be distributed
in both directions and the length of the expansion equaliser
Length change ( ∆l ) in mm deformation. Position it as close to the middle of the straight
required will be halved. It is recommended that tube saddles with
Graph 2: Nomogram for calculating the situation Fig. 14 a rubber inlay are used as this muffles any possible noise and
Expansion compensator L (mm) vibration and provides a better distribution of the stresses.
b

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