| Welding Methods SRPP and SRVF piping systems are assembled using reliable
thermal fusion. Simtech recommends socket welding for systems up to 1-1/4". Butt
fusion welding should be used for systems 1 ½" and larger.
Weather Resistance
Nearly all thermoplastics used for piping require
stabilizers to reduce the effects of sunlight and oxygen. PVDF is the major exception in
that it suffers no significant degradation when used outdoors. All other materials are
generally compounded with UV stabilizers and anti-oxidants to retard the rate of
degradation. While this procedure is effective, it does not totally eliminate the
phenomena. To maximize the service life of a system, it can be covered, coated, wrapped or
painted.
Moisture Absorption
SR Series PP and SRVF PVDF are water repellent. There
is no swelling or dimensional change. A slight weight gain found in tests is due merely to
traces of moisture on the surface.
Resistance
To Rodents and Micro-Organisms
Rodents endeavor to sharpen their teeth by gnawing
hard objects. This applies to timber, soft metals and plastics, which neither in terms of
taste nor in terms of odor encourage consumption of the material. However, because the
smooth surface of polypropylene and PVDF do not provide enough grip for teeth there are
virtually no attempts by rodents to gnaw at pipe or the surface of flat panels.
The raw material distributed by SIMONA is not a
nutrient for micro organisms such as bacteria, fungi or spores and therefore is not
attacked by them. This also applies in respect to bacteria which have a sulfate reducing
effect.
Electrical
Conductivity
The materials PP and PVDF, like all other plastics,
form part of the group of electrically insulating materials. This includes all materials
which have an impedance in excess of 109 Ohms is exceeded, then the material should be
categorized as electrostatically chargeable. In connection with the construction of
plastic pipe systems, electrostatic charges have to be taken into consideration, if media
are transported which are not electrically conductive or if the pipes are to be installed
in areas which are subject to explosion hazard. The transport of gases or liquids which
can ignite is only free from risk, if a closed system is used. In addition, it is possible
to reduce the risk of charging by reduced conveying speed. Explosive atmospheres in
areas in which plastic pipe is to be installed can be avoided by careful ventilation, or
by ionizing the air, so that the plastic does not become electrostatically charged. Since
electrostatic charges are rarely produced when the relative humidity is in excess of 65%,
an increase in the humidity is frequently another further solution to the problem.
It is fundamentally possible to make electrically non-conducting plastics into plastics
that are electrically conductive. Manufacture of certain pipe made from electrically
conductive PP or PVDF is possible, but require minimum order quantities for both
materials.
Pressure
Rating and Service Life
Pressure Rating for plastic piping is normally
expressed based on a 20° C (68° F) continuous operating temperature, i.e. 150 PSI at
approximately 68° F. Higher continuous temperature results in a lower pressure rating in
accordance with procedures outlined by ASTM D-2837 and the Plastic Pipe Institute
(Division of SPI). The expressed pressure rating of plastic piping represents 50% of the
pipes burst pressure after 100,000 hours or 11.4 years of continuous service. Thus, the
pressure rating provides a 2:1 safety factor at 100,000 hours service. It is then assumed
that the theoretical time to failure is 50 years.
SR Series Polypropylene piping is offered as SR150,
SR90 and SR45, indicating 150 PSI, 90 PSI and 45 PSI respectively. These ratings were used
to avoid confusion in the market place. We chose to indicate pressure ratings that matched
the industry norm.
PVDF Pipes
There is no pipe standard for PVDF material. In the
past, the wall thickness have been fixed by the tooling available for PP, PE-HD and PVC
piping. Hence they are not uniformly loaded.
Pipes Under External Gauge Pressure
External gauge pressure is the same as the difference
between external and inner pressure. Accordingly it is also possible to provide
information about the pipe loading when there is a vacuum in the interior.
Annealed
SR Series PP and PVDF pipe
SIMONA pipes are extruded in accordance with the
latest state of the art, with the minimum possible stresses. SIMONA PP Pipes and
SIMONA PVDF Pipes are, in addition, subjected to a thermal after-treatment, which
significantly reduces the stresses in the pipe wall caused by the extrusion process.
The post-treatment has the following beneficial effects on the pipe properties:
- Low shrinkage- important for socket joints or when the
pipes are subsequently heated
- Longer life, even with significant chemical
loading-especially important when used near limit conditions
- Increased impact resistance
- Increased dimensional stability
Radiation
Radiation Resistance Both Polypropylene and PVDF
posses resistance to high energy radiation. With regard to the order of magnitude, the
lethal dose for human beings is approximately 0.0006 Mrad. From this it can be concluded,
that PP and PVDF can be used in rooms in which humans are allowed to remain constantly.
Testing
During the manufacture of PP Pipes, SIMONA uses the
Chromic Acid Test. This in-house check of PP pipes has been used for some 10 years and has
always been withstood only by pipes with very low stresses, i.e., pipes which have been
Thermally Post-Treated. Chromium Salts (CRO3) are dissolved in water. More salt is
added to the water than can be dissolved. In this way, there is always sediment at the
bottom, which ensures maximum concentration in the supernatant liquid. The Chromic
Acid is heated to 40° C and continuously stirred during the duration of the test. The
specimen pipe is stored in the test fluid for 24 hours. During this test, the pipe is
removed several times from the liquid and visually checked for cracks. If there are
excessive inherent stresses, then the inside pipe wall will start to crack. In the case of
thick-walled pipes, it is possible for these cracks to extend through the entire wall
thickness causing the test specimen to be destroyed. |