The Basics

Composite Material

Woven roving laminate being consolidated — Woven roving laminate being consolidated

Reinforcements for strength - glass, carbon, synthetics, fibres, flakes
Thermoset resin matrix protects reinforcement and transfers loads to reinforcement - isophthalic, vinyl ester, epoxy resins
Manufacturing methods varied - contact moulding, filament winding, spray up, resin transfer moulding, prepregs, pultrusion
All fibreglass pump station for residential wastewater

Features of Fibreglass

High strength/weight ratio
Ease of fabrication - eg complex shapes, coloured
Fibres can be placed where the loads are
Dimensional stability - shapes can be duplicated accurately
Good weathering properties - eg can be placed outside
Good chemical resistance - with correct resin choice
Proven performance worldwide in industry for over 50 years

Stress & Strain

Ultimate Strength

Yield and Ultimate Strength are same
Ultimate Strength reduces with increasing temperature
When failure does occur it can be sudden and dramatic
Failure initiates at point of max stress

Good Design

Use high safety factors, SF = 5 minimum for structural FRP
Build to standards
Analyse stresses fully with FEA (Finite Element Analysis)
Ensure no over-stressing can occur
Avoid stress concentration points
Maintain regular inspections
If cracks or “weeping” occur, initiate maintenance immediately

LEFT: Fibreglass tank failure can be sudden and dramatic. Failure initiated from stress point 3 years after installation. Tank by another manufacturer. RIGHT: Polyethylene manhole failed under buried load at temperature. — LEFT: Fibreglass tank failure can be sudden and dramatic. Failure initiated from stress point 3 years after installation. Tank by another manufacturer. RIGHT: Polyethylene manhole failed under buried load at temperature.

Creep

What Happens

Ultimate Strength of FRP under load (pipes, tanks) reduces with time
Can lead to failure some years after installation
Reduction in Ultimate Strength depends on service temp and HDT (heat distortion temp) of resin

Good Design

Use higher safety factors for FRP under constant load ... minimum 10, eg for tanks and pipes
Use resin with HDT preferably 20ºC above max service temp
Avoid stress concentration points

LEFT: FRP tank and piping by ARMATEC at Pulp & Paper site handling bleach filtrate. Tank handles over-pressurisation from filters on floor above. RIGHT: Tank by others has crack in tank bottom knuckle due to incorrect lug design — LEFT: FRP tank and piping by ARMATEC at Pulp & Paper site handling bleach filtrate. Tank handles over-pressurisation from filters on floor above. RIGHT: Tank by others has crack in tank bottom knuckle due to incorrect lug design

Chemical Resistance

Fibreglass has wide range of corrosion resistance depending on resin selection, and is ideal for industrial applications. See How do I choose the right resin for my fibreglass products for more information.

Used for corrosive chemical storage, corrosive gases and liquids in a scrubber, and for combinations of corrosive chemicals in manholes and neutralisations sumps in an effluent stream. All the above installations are by ARMATAEC — Used for corrosive chemical storage, corrosive gases and liquids in a scrubber, and for combinations of corrosive chemicals in manholes and neutralisations sumps in an effluent stream. All the above installations are by ARMATAEC

Standards & QA

Standards to specify include:

AS 2634 - good all round standard used in NZ and Australia - still in use and in process of being superceded.
BS 4994 - for tanks and pipes especially
EN 13121-3-2004 - European standard
ASTM RTP1 - USA standard includes pressure vessels
AS/NZS 3751 - FRP pipe for public utilities
AS/NZS 2566 - for buried flexible pipelines
AS/NZS 1170 - for seismic and wind loads

Quality Assurance available

ISO 9001 Accreditation
Materials traceability
Design Audits
Standardised laminates tested (see table)
QA checks during manufacture
Post fabrication thickness checks
Post cure Barcol hardness checks
On site QA logs for coatings and linings
Coatings and linings - sparktesting
Coatings and linings - thickness check

Quality Assurance Tools Used by ARMATEC: Left - Ultrasonic thickness testing of fibreglass laminates; Centre - Spark testing tank lining for pinholes; Right - Measuring thickness of applied coating — Quality Assurance Tools Used by ARMATEC: Left - Ultrasonic thickness testing of fibreglass laminates; Centre - Spark testing tank lining for pinholes; Right - Measuring thickness of applied coating

Barrier Coatings

Key Success Criteria

Withstand chemical attack - choose correct resin
Resist permeation - less than 0.1 perms (ASTM E-96) or impedance greater than 1 x 10^8 ohm-sq.cm at 0.1Hz per EIS testing
Withstand other service conditions - eg abraision, flexing, cleaning, temperature fluctuations, physical abuse
Properly designed and prepared substrate - cleaned, steel blasted to minimum profile, concrete surface strength adequate
Be installed correctly - using specifications and QA procedures

Lifecycle Cost (LCC) Analysis

LCC is better than Initial Cost in evaluation that relative cost of a coating. Costs above are current day costs. No allowance is made for downtime or lost manufacturing time when coatings replaced.

Motunui methanol plant demin neutralisation sump below pipework (left) lined in 1983 by ARMATEC with barrier coating (right). In daily use for over 20 years. Maintenance costs during this time have been almost zero. — Motunui methanol plant demin neutralisation sump below pipework (left) lined in 1983 by ARMATEC with barrier coating (right). In daily use for over 20 years. Maintenance costs during this time have been almost zero.

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