Mesman A0 Poster LESAM.indd

Condition assessment of PVC water mains
G.A.M. Mesman1,*, B. Schultz2
Introduction
The Dutch drinking water network has a total length of about 116.000 km.
More than 50% of this network is made of PVC pipes and the cohort has
an average age of about 30 years, ranging from 60 to 0 years. The failure
rate, as recorded systematically in a national database, shows to be low
(0.025 failure/km/year). There is no clear time dependency in the failure
pattern, which can be explained by earlier research results showing the
material not to deteriorate under normal ground conditions.
Failure is due to overloading of the pipe or insufficient initial quality.
Three test methods are developed and tested to determine the (initial)
quality of the PVC: the failure break surface inspection, the resistance
of the material to DiChloroMethane at a specified Temperature (DCMT)
test and the Resistance against Slow Crack Growth (RSCG). With these
test methods failures can be analysed together with the loading pattern
to determine the cause of failure and which subsequent action is best. A
protocol for testing is developed that helps to determine the appropriate
and most economical asset management strategy.
60
50 year
50
σY (MPa)
Condition
PVC main?
25 year
40
30
20
10
0
Yes
2
0
Figure 2. Result from DCMT test “Attacked”.
1
1
2
3
4
5
6
log t (sec)
3
7
8
9
10
y = -3.5475x + 43.691
Figure 1. Failed PVC drinking water main..
Failed
pipe?
No
Yes
Particles
present?
4
Figure 4. Particles in the PVC matrix
on the surface of the crack, probably
crystaline PVC. Growth rings caused
by slow crack growth can be seen
around the particle.
No
DCMT =
attacked
Yes
Figure 3. Result of a test for the
resistance against slow crack
growth, σγ below 12.5 MPa for
50 years. The 95% confidence
interval lies between the dotted
lines.
No
RSCG50y
< 12.5 MPa
Yes
No
Yes
Failure rate
high?
No
No
Failure rate
high?
Yes
Bad quality PVC.
Replace main
Replace pipe
and monitor
failure rate of main
Failure rate (#/km/year)
0.07
0.06
0.05
Yes
freq USTOREweb
0.04
0.03
0.02
0.01
0
1956- 1961- 1966- 1971- 1976- 1981- 1986- 1991- 1996- 2001- 20061960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
5
Years
Wrong choice SDR.
Replace main
Figure 5. Averaged failure frequency of PVC water mains for
the years 2009-2010 for the different years of construction.
Figure 6. Scheme for condition assessment of PVC drinking water mains.
Conclusions
Condition assessment of PVC pipes will give an answer to the question which part of a failed main has to be replaced. For the condition
assessment of PVC pipes three techniques have to be combined. These techniques are:
• Visual inspection of the cracks of failed pipes on particles;
• DCMT test on the investigated pipe;
• Assessment of the resistance against slow crack growth.
By using a protocol for ranking the techniques the total number of experiments can be limited. An answer to the question whether the
whole main or just the failed pipe has to be replaced will follow from the protocol.
1.
KWR Watercycle Research Institute, PO Box 1072, 3430 BB Nieuwegein, the Netherlands
Watercycle Research Institute
2.
OASEN, PO Box 122, 2800 AC Gouda, the Netherlands
* Corresponding author:
[email protected]
This project was conducted
within the Joint Research
Program of the Dutch
water companies
110802gm