Silane cross-linked polyethylene pipe INTERSOL ... - Watts Industries

SILANE CROSS-LINKED POLYETHYLENE PIPE
We shall show an example of calculating the factor of safety :
12
Suppose we have a pipe with dimensions 16 x 2 - Max. operating pressure = 3 bar
Max. operating temperature = 70°C - Required duration = 50 years
On the basis of the above data, we can deduce the equivalent force:
e =
P x (de - s)
20 x s
=
3 x (16 - 2)
20 x 2
= 1,05 N mm 2
from the regression curve at 70°C it can be seen that max. stress for the period of 50 years is equal to:
max = 5,4 N/mm 2
hence the factor of safety is as follows:
fs = max
e
= 5,4 = 5,1
1,05
For example, in accordance with UNI 9338 standard, two classes of nominal pressure are defined (max. permissible
pressure for continuous duty with water at 20°C), namely PN10 and PN16, depending on the dimensions, as given
table 11. Therefore having defined a factor of safety equal to 1.3, table 12 shows the safety operating pressures for
different temperature and time ranges.
Table 11 Table 12
Nominal
O.D.
Average
O.D.
Wall thickness
PN 10 PN 16
10 10 +0,3 - 1,8 +0,1
12 12 +0,3 - 2,0 +0,2
14 14 +0,3 - 2,0 +0,2
15 15 +0,3 2,0 +0,2 2,5 +0,2
16 16 +0,3 2,0 +0,2 2,5 +0,2
17 17 +0,3 2,0 +0,2 2,3 +0,2
18 18 +0,3 2,0 +0,2 2,5 +0,2
20 20 +0,3 2,0 +0,2 2,8 +0,2
22 22 +0,3 2,0 +0,2 3,0 +0,3
25 25 +0,3 2,3 +0,2 3,5 +0,3
28 28 +0,3 3,0 +0,3 4,0 +0,3
32 32 +0,3 3,0 +0,3 4,4 +0,4
Temperature (°C) Factor Duration Max.permissible Max. permissible
of safety (years) safety force operating pressure
(MPa)
(bar)
PN 10 PN 16
up to 60°C 1,3 50 5,0 10 16
over 60°C
up to 80°C
1,3 50 3,8 6 10
over 80°C
up to 95°C
1,3 10 3,2 6 10