PVC Pressure Pipe Endures Over Ten Million Cycles

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the water distribution system as well as the
sanitary and storm sewer systems. A majority of
North American cities are recog- nizing the
efficiency and high reliability of PVC pipes by
authorizing their use for infrastructure
construction. The Burroughs of Sainte-Foy
Sillery decision makers have gone one step fur-
ther in recognizing the superior performance of
the PVC material by specifying its sole use in
order to promote sustainable development. In
addition to the citizens living in the bur-
roughs, all Quebec City citizens are benefit-
ing from the superior performance of PVC water
pipes their use allows the city engi- neers to
devote their efforts to the sectors
CONTINUED FROM PAGE 7
detection programs are not necessary in the
sectors where the water distribution lines are
constructed with PVC pipes. This fact allows us
to concentrate our limited resources where they
are most needed, in the sectors built with iron
pipe, states Mr. Perreault, who points out that
flushing is also a thing of the past for the PVC
sectors. To this day, the Technical Services
officials for the West Infrastructures Division
of Quebec City, which includes the Burroughs of
Sainte- Foy-Sillery and Laurentien, are
specifying PVC pipes for constructing and
rehabilitating its water distribution system.
While Mr. Proulx is
Mr. Perreault (right) was one of the decision
makers who laid the groundwork for lasting
infrastructure by using PVC for the Burrough of
Sainte-Foy. Mr. Desrosiers (left) is a part of
the current team that continues the legacy of
lasting infrastructure by using PVC for Quebec
Citys cities are struggling to breach the
infrastruc- ture gap, which is caused mainly by
corro- sion, there are solutions available that
will allow the building of reliable
infrastructure within a sustainable development
concept. The professionals of the
Sainte-Foy-Sillery Laurentien Burroughs of
Quebec City have shown it is possible. Follow
their lead and you will soon be writing one of
the most durable chapters of your own citys
history.
THIS FACT ALLOWS US TO CONCENTRATE OUR LIMITED
RESOURCES WHERE THEY ARE MOST NEEDED, IN THE
SECTORS BUILT WITH IRON PIPE
now enjoying a well-deserved retirement, Mr.
Perreault is supported by a new technical team,
which includes Mr. Donald Desrosiers, P. Eng.
Mr. Desrosiers also recognizes the sever- al
qualities of PVC pipes that make it a reliable
investment for underground infrastructure for
where conventional materials are currently
failing due to corrosion, knowing that the PVC
sectors will continue to offer their supe- rior
level of performance. At this juncture where all
North American
PVC Pressure Pipe Endures Over Ten
Million Cycles Figure 1 Test Apparatus for
cyclic testing. The blue pipe is AWWA C900,
DR18, from Phase I. The white pipe is ASTM
D2241, SDR41, introduced in Phase II
By Craig Fisher, P.E. Technical Director
over 10 million cycles without any failures. Ten
Million! That is a one with seven zeros after
it 10,000,000! The researchers at Utah State
University (USU) cycled the DR 18,
which has a Pressure Class of 150 psi, between
185 psi and 235 psi for exactly 10,209,535
cycles. At 18 cycles per minute, it took a total
of 394 days and two research phases to finish
the testing. The test was stopped without any
of
the AWWA C900 specimens fail- ing. The pump and
the pressure relief valve did not fare as well.
During the testing, USU failed six pumps and
five relief valves in order to log ten million
cycles on
Nof six-inch, DR 18,
o, it is not a typographi-
cal error. Ten specimens
AWWA C900 pipe endured
CONTINUED ON PAGE 10
P V C P I P E N E W S S P R I N G 2 0 0 4
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TABLE 1. TEST PRESSURES AND STRESSES TABLE 1. TEST PRESSURES AND STRESSES TABLE 1. TEST PRESSURES AND STRESSES TABLE 1. TEST PRESSURES AND STRESSES TABLE 1. TEST PRESSURES AND STRESSES TABLE 1. TEST PRESSURES AND STRESSES TABLE 1. TEST PRESSURES AND STRESSES TABLE 1. TEST PRESSURES AND STRESSES
Test Specimen Description Minimum Pressure (psi) Maximum Pressure (psi) Mean Stress (psi) Stress Amplitude (psi)
One DR 18, AWWA C900, PC 150 psi 185 235 1787 213
Two SDR 41, ASTM D2241, PR 100 psi 82 123 2000 400
Three SDR 41, ASTM D2241, PR 100 psi 0 154 1500 1500
Four SDR 41, ASTM D2241, PR 100 psi 56.5 149 2000 900
Uni-Bell first contracted with USU in 1999 to
re-evaluate the cyclic capabilities of PVC pres-
sure pipe. At the time, there were two
competing theories.
edition of The Handbook of PVC Pipe Design and
Construction
lished his finding in February of 2001. That
testing showed that the cyclic life of PVC was a
func- tion of two variables - not one. PVC pipe
fatigue is a function of both the mean stress
and the stress amplitude. (The fourth edition
of the Handbook, pub- lished in August of 2001,
shows Mosers 2001 theory.) Phase I The first
phase involved only AWWA C900 pipe. As mentioned
earlier, this pipe was cycled from 185 psi to
235 psi, which resulted in an average stress of
1,787 psi and a stress amplitude of 213 psi.
Vinsons formula predicted failure at 322,000
cycles. After success- fully logging 3.5 million
cycles, the first phase of testing was conclud-
ed and a new cyclic theory for PVC was
published. However, Dr. Moser stated that more
data points were needed in order to fine-tune
the design chart that he developed. Phase II So
in April of 2001, Uni-Bell entered its second
contract on this project with USU in order to
continue the work begun in Phase I. This time,
ASTM D2241 PVC pipe would be subjected to
pressures and amplitudes well beyond that
recommended in the design standards. Also, the
testing on the AWWA C900 pipe would be
re-started. SDR 41, ASTM D2241 pipe, with a
Pressure Rating of 100 psi, was selected for the
abusive cyclic
CONTINUED FROM PAGE 9 the PVC pipe. The test
set-up is shown in Figure 1 on page 9. The blue
pipe is the AWWA C900 pipe, and the white pipe
is six- inch, SDR 41, ASTM D2241 pipe. This
testing was a part of Phase II of USUs research
project on the cyclic capabilities of PVC pres-
sure pipe. In the Spring 2001 edition of the PVC
News, we reported on the research results from
Phase I and said that more data points would be
collected. Well the data is in, and the results
are impressive. Background
shows Vinsons theory.) The Europeans had a
competing the- ory that stated the cyclic life
was
DURING THE TESTING, UTAH STATE UNIVERSITY FAILED
SIX PUMPS AND FIVE RELIEF VALVES IN ORDER TO LOG
TEN MILLION CYCLES ON THE PVC PIPE.
The first theory was developed by Vinson and
stated that the cyclic life of PVC was a
function of peak stress only. (The third
a function of only the stress amplitude. Dr.
Moser complet- ed the first phase of the testing
in the summer of 2000 and pub-
Figure 3 New cyclic design chart updated after
collecting extra data points from the second
phase of testing.
CONTINUED ON PAGE 19
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P V C P I P E N E W S S P R I N G 2 0 0 4
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The How-To Handbook of PVC Pipe 522 PAGES
The only complete reference for those who plan,
design, install and operate PVC sys- tems for
municipal water mains, sanitary sewer and storm
water drainage systems. If you are planning, or
now operate a PVC pressure or non-pressure
system, this handbook is a must!
O N L Y 4 0 P E R C O P Y (Includes
postage and handling for US and Canadian orders.)
Payable in US Funds, Texas Residents add 8.25
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Figure 2 The cyclic pressures applied during
testing followed a sawtooth pattern.
CONTINUED FROM PAGE 10
pressure combinations. Using pipe with a higher
dimension ratio allowed higher stresses to be
generated in the pipe wall at lower pressures.
Generating the same stresses in DR 18 would
require a prohibitively expensive pumping system.
Also, the researchers learned in Phase I to
expect equipment failures. The extreme pressures
take their toll on the equip- ment, and so,
replacement pumps were a large part of the
equipment cost in the research budget. Table 1 on
page 10 shows the average pressure and amplitude
for the four pressure combinations. The corre-
sponding wall stresses are also listed. The
pattern of cyclic pressure applied was a
sawtooth. The computer screen in Figure 2
(above) displays the pressure wave applied. The
minimum and maximum pres- sures on Test One were
regulated to within /- 5 psi. A more accurate
control system was used on Test Two, Three, and
Four. Pressures were regulated to within /- 3
psi. Temperature was 22C /- 2 (71.6F /-
3.6). Cyclic Design Graph With the help of the
new data points, a fine-tuned design graph is
now available. It appears in Figure 3 on page
10. The chart is a wonderful design tool for
engineers involved in turf irrigation or sewer
force main design. Those types of systems
sometimes see surges of greater magnitude with
greater frequency. We plan a follow-up article
that provides a cyclic design example for a force
main system.

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