6
between skirts. However, skirts or contributing stars should
be distributed between the rings as evenly as practical.
DESIGN FOR FABRICATION
In the last two Sections, the challenges of the design and
fabrication were discussed. The most common practice in
the industry is designing the flange first and then devel-
oping a plan to fabricate it. Since the fabrication plan is
typically not straightforward, the final achieved thicknesses
are often different from the designed ones. In addition,
there is always a risk of making a low-quality flange due to
improper lamination planning.
Ideally, the fabrication plan should be made concur-
rently with the design of the flange. That is, creating detailed
specifications for numbers, types, shapes, dimensions, and
layer sequences during the design. This approach allows us
to have a detailed fabrication plan and a compliant design
simultaneously. Additionally, other considerations, such as
pipe thickness for integral flanges and the butt joint length
for flange-on-pipe, need to be properly incorporated into
the design. To achieve this, numerous interconnected vari-
ables and trial-and-error practices come into play, which
makes it impractical for the designer to manually keep track
of all changes.
RPS has developed an internal tool (see Figure 3) that
makes the design for fabrication possible. This tool is devel-
oped by VBA programming. After establishing the inputs
of the design, including size, pressure, design factors, type
of flange, etc., the designer can start by applying different
types of layers. By adding each layer, the tool updates the
achieved safety factors, dimensions, geometry, etc. It also
keeps track of potential interferences between the hub and
backing ring or spot face depth and warns the designer
of any potential issues while providing visual aids of the
achieved profile of the flange.
This tool makes the design and fabrication planning
process very quick while reducing the chance of making
mistakes. Once the design is completed, a detailed fabrica-
tion specification is also prepared.
FRP FLANGE INSTALLATION
Proper installation of flanges is the last step of using FRP
flanges. In this Section, some of the most important factors
that play a role in the successful installation of flanges are
discussed.
Ensure that the gasket used for installation is the same
gasket used in the flange’s design. This information should
be provided to the designer as an input.
• Using sealing rings on the flange face makes sealing
easier when the gasket is flat. Use flat-faced flanges
when the gasket has sealing ribs.
• Ensure that the gaskets used in abrasion systems
have an inside diameter of at least ¼” larger than the
pipe’s inside diameter. This prevents the gasket from
protruding into the flow and causing turbulence,
which could result in an abnormally high rate of pipe
erosion.
Alignment
Ensuring that mating flanges align well is critical, as mis-
aligned flanges may be damaged during the bolting process.
Torquing the bolts is typically the step where installers
deviate from the instructions provided by the FRP flange
fabricator. This mainly occurs because they exceed the bolt
torque values recommended by the vendor
• The maximum bolt torque should be provided by the
fabricator/designer of the flange
• A torque wrench should be used. The use of air- pow-
ered or electric wrenches is not recommended unless
they have an in situ torque control feature.
• Use either Teflon-coated or well-lubricated bolts,
unless otherwise specified by the fabricator/vendor
• Start with 30% of the max torque value in a criss-
cross sequence.
• Repeat the previous step with 60% of the maximum
torque.
• Repeat the previous step with 100% of the maxi-
mum torque.
• Torque all bolts to 100% one more time with a sim-
ple circular pattern (not crisscross)
It is not recommended to mate an FF FRP flange with
an LJ flange or valve with lining. In situations where it is
inevitable, using a spacer ring or an FRP Lap Joint flange
is advisable, as it provides a solution that minimizes stress
levels. The spacer ring should have higher stiffness than the
gasket.
CONCLUSION
The challenges surrounding the design and fabrication
of Fiber Reinforced Polymer (FRP) flanges are complex and
multifaceted. FRP materials offer numerous advantages
over traditional steel counterparts, such as corrosion resis-
tance, lightweight properties, chemical compatibility, cus-
tomization options, and reduced maintenance costs. These
benefits make FRP an attractive choice for various indus-
tries, including mining and chemical processing, where the
reliability and longevity of components are crucial.
between skirts. However, skirts or contributing stars should
be distributed between the rings as evenly as practical.
DESIGN FOR FABRICATION
In the last two Sections, the challenges of the design and
fabrication were discussed. The most common practice in
the industry is designing the flange first and then devel-
oping a plan to fabricate it. Since the fabrication plan is
typically not straightforward, the final achieved thicknesses
are often different from the designed ones. In addition,
there is always a risk of making a low-quality flange due to
improper lamination planning.
Ideally, the fabrication plan should be made concur-
rently with the design of the flange. That is, creating detailed
specifications for numbers, types, shapes, dimensions, and
layer sequences during the design. This approach allows us
to have a detailed fabrication plan and a compliant design
simultaneously. Additionally, other considerations, such as
pipe thickness for integral flanges and the butt joint length
for flange-on-pipe, need to be properly incorporated into
the design. To achieve this, numerous interconnected vari-
ables and trial-and-error practices come into play, which
makes it impractical for the designer to manually keep track
of all changes.
RPS has developed an internal tool (see Figure 3) that
makes the design for fabrication possible. This tool is devel-
oped by VBA programming. After establishing the inputs
of the design, including size, pressure, design factors, type
of flange, etc., the designer can start by applying different
types of layers. By adding each layer, the tool updates the
achieved safety factors, dimensions, geometry, etc. It also
keeps track of potential interferences between the hub and
backing ring or spot face depth and warns the designer
of any potential issues while providing visual aids of the
achieved profile of the flange.
This tool makes the design and fabrication planning
process very quick while reducing the chance of making
mistakes. Once the design is completed, a detailed fabrica-
tion specification is also prepared.
FRP FLANGE INSTALLATION
Proper installation of flanges is the last step of using FRP
flanges. In this Section, some of the most important factors
that play a role in the successful installation of flanges are
discussed.
Ensure that the gasket used for installation is the same
gasket used in the flange’s design. This information should
be provided to the designer as an input.
• Using sealing rings on the flange face makes sealing
easier when the gasket is flat. Use flat-faced flanges
when the gasket has sealing ribs.
• Ensure that the gaskets used in abrasion systems
have an inside diameter of at least ¼” larger than the
pipe’s inside diameter. This prevents the gasket from
protruding into the flow and causing turbulence,
which could result in an abnormally high rate of pipe
erosion.
Alignment
Ensuring that mating flanges align well is critical, as mis-
aligned flanges may be damaged during the bolting process.
Torquing the bolts is typically the step where installers
deviate from the instructions provided by the FRP flange
fabricator. This mainly occurs because they exceed the bolt
torque values recommended by the vendor
• The maximum bolt torque should be provided by the
fabricator/designer of the flange
• A torque wrench should be used. The use of air- pow-
ered or electric wrenches is not recommended unless
they have an in situ torque control feature.
• Use either Teflon-coated or well-lubricated bolts,
unless otherwise specified by the fabricator/vendor
• Start with 30% of the max torque value in a criss-
cross sequence.
• Repeat the previous step with 60% of the maximum
torque.
• Repeat the previous step with 100% of the maxi-
mum torque.
• Torque all bolts to 100% one more time with a sim-
ple circular pattern (not crisscross)
It is not recommended to mate an FF FRP flange with
an LJ flange or valve with lining. In situations where it is
inevitable, using a spacer ring or an FRP Lap Joint flange
is advisable, as it provides a solution that minimizes stress
levels. The spacer ring should have higher stiffness than the
gasket.
CONCLUSION
The challenges surrounding the design and fabrication
of Fiber Reinforced Polymer (FRP) flanges are complex and
multifaceted. FRP materials offer numerous advantages
over traditional steel counterparts, such as corrosion resis-
tance, lightweight properties, chemical compatibility, cus-
tomization options, and reduced maintenance costs. These
benefits make FRP an attractive choice for various indus-
tries, including mining and chemical processing, where the
reliability and longevity of components are crucial.