How to Select the Proper Industrial Piping Material Thermoplastic

PlasticPipeLine
How to Select the
Proper Thermoplastic
Industrial Piping Material
by David A. Chasis
P
lastic piping is used to move more fluids
than any other piping material in the world.
Why is it so widely used? Plastics are more
durable, easier and safer to install, environmentally sound, and cost-effective than most other
piping materials. Yet, due to the many available
plastic piping systems, selecting the correct piping product could be a daunting task. The two
keys for choosing the proper plastic piping material are: knowing the complete project’’s service
conditions and the most cost-effective and suitable materials for these service conditions.
Service Conditions: The more you know about
the factors of a particular field application, the
more likely you are to select the proper piping
material. An information checklist for all piping
installations may include the following, with the
most important factors in bold print:
•• Type or purpose of application: application
type (chemical processing, water lines, sewage, irrigation, etc.); above or below ground;
any prolonged exposure to sunlight; openedor closed-loop system; quick-closing valves in
system.
•• Type of fluids to be transported: chemical
compatibility of pipe, valves and fittings, any
special fluid data such as high particulate matter, viscosity, specific gravity, velocity, etc.
•• Maximum allowable working pressure: working pressure varies for each plastic piping component and may be limited to the maximum
allowable working pressure for a particular
product such as valves, flanges or unions.
•• Temperature range: temperature limitations
vary for each plastic piping material and directly affect working pressure capability of all
plastic products coming in contact with the
transferred fluid.
•• Code restrictions: depending on the application, local, state and federal codes may restrict
the selection of a particular piping material.
•• Estimated life of piping system: in very severe
service conditions, various piping materials
may have limited life and affect which piping
system will last the longest.
•• Preferred method of joining: depending on
the availability of utilities (electric, gas or neiFebruary/March 2013 The IAPD Magazine
ther) as well as the experience of the installation crew, selection of the joining system could
be important.
With the conditions of service known and
knowledge of the piping material properties, a
specifying engineer or end user is well on his/
her way to selecting the best piping material for
the project.
Plastic Piping Materials: There are five commonly used thermoplastic industrial piping materials in the United States, all of which have
different temperature and allowable working
pressure ranges. In most cases all the plastic piping materials can withstand temperature lows of
0°F (-18°C). The only caveat to remember with
thermoplastic piping at lower temperatures is
that the piping system becomes more brittle.
The listing below indicates the maximum temperature capability of each piping material. Keep
in mind that with thermoplastic piping, as the
temperature increases, the allowable working
pressure decreases. Therefore, only drainage
applications, in most cases, can be used at the
maximum temperature rating.
•• CPVC (chlorinated polyvinyl chloride): similar
in properties to PVC (polyvinyl chloride); can
handle temperatures up to 210°F (99°C); used
in pressure and chemical drainage piping systems as well as hot and cold water distribution
and fire sprinkler systems.
•• PE (polyethylene): several material compound
types depending on the application; the broadest range of pipe diameters; mostly used
in belowground applications; most PE piping
systems have temperature capabilities of up
to 160° (71°C), however, one fairly recent
material, polyethylene raised temperature
(PE-RT), can withstand temperatures up to
210°F (99°C); a preferred piping material for
natural gas distribution.
service allow, PVC is the most specified and
installed plastic piping material in the world;
maximum temperature up to 140°F (60°C); in
most cases PVC is the lowest cost piping material for a myriad of applications.
•• PVDF (polyvinylidene fluoride): has the best
chemical resistance properties and highest
temperature capability 275°F (135°C) of any of
the listed piping materials; mostly immune to
ultra-violet degradation; the preferred piping
material in ultra-high purity water systems.
[Note: Acrylonitrile butadiene styrene (ABS) and
crossed-linked polyethylene (PEX) are not listed
since most of these excellent plastic piping materials are used in the United States for residential/
commercial, not industrial, applications.]
Each of these plastics has properties that may
or may not be suitable for a particular application. To determine the proper piping material,
you must compare the project’’s conditions of
service with that of the piping material’’s properties, breadth of product line and installed costs.
The best way to show how this process works is
by example.
Example —— Service Conditions: The following
listed service conditions are the basis for selecting
piping materials:
•• Application: metal ore smelting; above ground
•• Fluid: sulfuric acid with 70 percent concentration
•• Working pressure: 50 to 105 psi
•• Working temperature: 70 to 130°F (21 to 54°C)
•• Piping size: ½ to 6 inches
•• PP (polypropylene): very versatile material
for temperatures up to 180°F (82°C); the leading piping material in chemical drainage and,
because of its excellent chemical resistance,
can handle many corrosive pressure piping
applications.
Example —— Chemical Compatibility: The first
step is to determine the chemical resistance
of the fluid versus the piping material. There
are several published and well-tested chemical
resistance tables that list hundreds of chemicals
and their suitability to both plastics and metal
materials. On the next page is a snippet of a
typical chemical resistance chart pertinent to this
example. You can see after reviewing the chart
that PP and PE piping are not able to handle the
conditions of service shown.
•• PVC (polyvinyl chloride): when conditions of
Example —— Pressure Capability: Next you
www.iapd.org
PlasticPipeLine
Partial Chemical Resistance Chart
Chemical
PVC
Temperature (°F)
CPVC
PP
PVDF
PE
70
140
70
140
185
70
150
180
70
150
250
70
140
Sulfuric acid, 50% R
R
R
R
R
R
R
R
NR
R
R
R
R
——
Sulfuric acid, 60% R
R
R
R
R
R
R
R
NR
R
R
R
R
——
Sulfuric acid, 70% R
R
R
R
R
R
R
NR
NR
R
R
R
R
——
Sulfuric acid, 80% R
R
R
R
R
R
R
NR
NR
R
R
——
R
NR
Sulfuric acid, 90% R
R
NR
R
R
R
R
NR
NR
R
R
——
R
NR
Sulfuric acid, 93% R
R
NR
R
R
R
R
NR
NR
R
R
——
R
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
——
NR
NR
Sulfuric acid, 100% NR
R = Recommended
determine the working pressure capability of the
piping materials in the example. Thermoplastic
piping working pressure is affected by temperature, and in the case of schedule 40 and 80, piping
can vary with pipe diameter. The tables below
show the working pressure capabilities at ambient temperature 73°F (23°C) of the five piping
materials and the temperature correction factors
that are used to multiply the factor times the
ambient pipe pressure rating in order to obtain
the maximum working pressure capability of each
piping material. As noted in the tables, PVC 6-inch
diameter pipe at ambient temperature has a
working pressure of 280 psi. The temperature
correction factor for PVC pipe at 130°F (54°C) is
shown as 0.30; therefore, multiplying 280 psi by
0.30 equals 84 psi. The conditions of service list
a maximum working pressure of 105 psi; hence,
only CPVC and PVDF piping are capable of handling the stated conditions of service.
Example —— Cost Comparison: The last step in
the selection process is to choose the more costeffective of the two qualifying piping materials.
Looking at the chart below it is evident that CPVC
is the winner as the PVDF piping system costs over
two and a half times that of CPVC.
There are industrial applications where temperatures exceed 275°F (135°C) and working pressures are well above 250 psi. For these conditions
of service, piping of glass-reinforced thermosetting resin and metal- and plastic-lined metal may
be the materials of choice. But for an estimated
80 percent of all industrial applications, thermoplastic piping systems should be the preferred
choice due to their durability, ease of use, environmental soundness and cost-effectiveness.
David A. Chasis is president of Chasis Consulting, Inc., author
of the book “Plastic Piping Systems” and a member of and
consultant to the Plastic Pipe and Fittings Association. Chasis
can be reached at Chasis Consulting, Inc., 329 The Hills Drive,
Austin, TX 78738 USA; (512) 261-9115, fax (512) 261-3518, email:
dchasis@gmail.com, www.davidchasis.com.
www.iapd.org
—— = No Information Available
NR = Not Recommended
Maximum Operating Pressure Ratings (psi) of Schedule 80
Pipings/Fittings at 73°F (23°C)
Nominal Pipe Size (in.)
PVC / CPVC
PE (SDR 11)
PP*
PVDF
3
370
160
190
250
4
320
160
160
220
6
280
160
140
190
Temperature Correction
Factors
for PipingFactors for Piping
Termperature
Correction
Operating Temp. (°F)
CPVC
PE
PP
PVC
PVDF
110
.77
.74
.80
.50
.75
120
.70
.63
.75
.40
.68
130
.62
.57
.68
.30
.62
CPVC: 0.62(280) = 174 psi
PVC: 0.30(280) = 84 psi (System max. is 105 psi)
PVDF: 0.62(190) = 118 psi
Estimated Installed
Costs of Six-Inch
Diameter
Piping
Systems*
Termperature
Correction
Factors
for Piping
Materials
Piping Costs (US$)
PVC Schedule 80
11,499
CPVC Schedule 80
14,374
Carbon Steel Schedule 40
18,932
Stainless Steel 304L Schedule 40
22,789
Stanless Steel 316L Schedule 40
45,835
PVDF Schedule 80
63,945
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Note: The example and charts shown are adapted from the “Thermoplastic Industrial Piping Systems Workbook” published by the Plastic
Pipe and Fittings Association (PPFA).
February/March 2013 The IAPD Magazine