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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 piping systems. Today, there are a
number of nationally recognized standards and specifications for fiberglass
tanks and 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 Materials
AWWA American Water Works Association
FM Factory Mutual Research
NSF National Sanitation Foundation
UL Underwriters Laboratories Inc.
What is Fiberglass?
Fiberglass tanks and 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 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.
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