Fiberglass Tank & Piping
Fundamentals
Fiberglass reinforced thermosetting plastic (“fiberglass”) first became a viable
alternative to protected steel, stainless steel and exotic materials in 1950.
That year centrifugal cast fiberglass piping was first used in the crude oil
production industry as a solution to corrosion problems. It was during the
1960’s that manufacturers began to develop nationally recognized standards and
test methods for fiberglass storage and fiberglass piping systems. Today, there are a
number of nationally recognized standards and specifications for fiberglass
tanks and fiberglass piping. While there are standards developed for military applications,
e.g., MIL standards for helicopter rotor blades, following is a list of civilian
organizations with published standards and specifications:
|
Fiberglass |
Civilian Organizations |
|
Tanks &
Piping |
- API American
Petroleum Institute
- ASME American
Society of Mechanical Engineers
- ASTM American
Society for Testing and Material
- AWWA American Water
Works Association
- FM Factory Mutual
Research
- NSF National
Sanitation Foundation
- UL Underwriters
Laboratories Inc.
|
What is Fiberglass?
Fiberglass tanks and fiberglass piping contain glass fiber reinforcement embedded in cured
thermosetting resin, hence the term Fiberglass Reinforced Plastic (FRP)
describes the fiberglass material system. This composite structure typically
contains additives such as pigments and dyes. By selecting the proper
combination of resin, glass fibers, additives and design, the fabricator can
create a product that meets the equipment designer’s performance standard.
Glass Fibers: All fiberglass begins as individual filaments of glass drawn from
a furnace of molten glass. Many filaments of glass are formed simultaneously and
gathered into a “strand” and a surface treatment “sizing” is added to maintain
fiber properties. Glass fibers are designed for several applications, some of
which are for applications in an acid, alkali or other chemical environment. The
mechanical strength of a fiberglass product depends upon the amount, type and
arrangement of glass fiber reinforcement within the material system and
increases proportionally with the amount of glass fiber reinforcement.
Resins: The second major component of fiberglass tanks and piping is the
thermosetting resin system. Thermoplastic resin systems is one of two basic
groups of resins, but is not used with glass fiber reinforcing. A comparison of
the two resin systems is shown below:
- Thermoplastics are resins that are normally solid at room temperature, but are
softened by heat and will flow under pressure. Typical applications include
household kitchenware, children’s toys, bottles and other common items.
- Thermosetting plastics are resins that undergo an irreversible reaction when
cured in the presence of a catalyst. They cannot be re-melted and are insoluble.
Fiberglass products use only thermosetting resin systems of which there are two
generic types, epoxy and polyester resins. The resin system is chosen for its
chemical, mechanical and thermal properties. Epoxy resins are used primarily for
the manufacture of small diameter piping, whereas polyester resins are commonly
used for large diameter piping and storage tanks. Polyester resins come in many
variations with different properties to resist acids, caustics and high
temperatures.
Resistance to corrosion in aggressive environments is one of the primary reasons
for specifying fiberglass tanks or piping. Typical types of corrosion do not
affect fiberglass. This would include galvanic, aerobic, pitting and
inter-granular corrosion which harms metals but not fiberglass. Although
fiberglass resists a wide range of chemicals and temperatures, it requires the
right design, fabrication and installation to match the appropriate application.
For example, fiberglass may be subject to chemical attack from hydrolysis,
oxidation, or incompatible solutions. However, the proper resin/glass matrix
will address this chemical attack.
Today, off-the-shelf or custom fiberglass tanks and fiberglass piping is used in corrosive
environments and high pressure (e.g. 60 psi) process applications. These
fiberglass systems are widely used in retail petroleum, exploration &
production, chemical, municipal and industrial applications. |
