|
Plastic
Valves Installed in a Metal Piping System
|
|
|
| |
Many
times people with a metal piping system are attracted to a plastic valve
or strainer because of its low cost compared to a stainless steel
or bronze one. And also for all of the benefits plastic offers (Click
here to see other benefits of plastic flow control products).
The engineer that designed that system chose metal pipe for a specific
application reason so you have to make sure a plastic component will
work.
Plastic components
can, however, be used successfully in metal systems. But the you
have to be aware of several factors that will effect the success of the
application. If these factors are not taken into consideration the chance
of success is reduced. Applied and installed correctly, however, the valve
or strainer will perform as expected.
First, you have
to be sure that the plastic valve or strainer will be used within its temperature
and pressure rating. Metal piping is often used because of high operating
temperatures. Make sure the temperature/pressure range of the application
is within the acceptable range for the plastic product you are considering.
Chemical resistance needs to be checked as well to insure that there will
not be a problem.
|
| Part of your
application analysis should include the potential for shock pressure generation,
i.e. water hammer in the system that could damage the plastic valve or
strainer. Things to look for include a system flow rate of greater than
8 feet per second, quick starting pumps, positive displacement pumps, fast
opening or closing actuated valves, and solenoid valves.
|
| Once its determined
that ALL of the application parameters are OK for the plastic component
it a good thing to look at how the plastic component is installed. Stress
on the plastic valve or strainer is the single most important installation
factor to consider. Stress can cause immediate damage or it can build up
over time and cause damage later on. There are several ways that this stress
can be induced during installation and/or operation.
|
| One is improper
alignment of the plastic component in the metal piping system. If either
one has to be forced into position it's sure to cause problems. Another
thing to look out for is over size face to face dimensions of the mating
pipe flanges as well as misalignment of the flanges.
|
| Thermal expansion
can be a problem is some applications. Expansion joints can help compensate
for this. Another solution is to install plastic pipe on the inlet and
outlet of the valve or strainer to isolate it from the metal pipe.
|
| Plastic valve
and pipeline strainers can be use successfully in many metal piping systems.
You just have to be aware of the all of the application parameters and
how they relate to the plastic component. Not all applications are the
same and the recommendations that have been made here may not apply in
all cases.
|
|
Back
to Hayward Back to PEP
|
|
Copyright
HAYWARD Industrial Products, Inc. 1999
|
Plastic
Valves Installed in Metal Piping System