Essential Guide to Inspecting Fiberglass Reinforced Plastic (FRP) Tanks

Fiberglass-reinforced plastic (FRP) tanks offer significant advantages, including high corrosion resistance, which ensures long-term durability and suitability for storing a variety of chemicals and fuels without degradation. Their lightweight nature makes them easier to transport and install, often resulting in lower installation costs and less need for structural support. Customization options allow for tanks to be built to specific dimensions and outfitted with features like internal baffles and heating elements. They are also UV resistant, making them ideal for outdoor use without the risk of sun damage. Additionally, their corrosion resistance and durability lead to lower maintenance requirements, and their non-conductive nature reduces electrical hazards, enhancing overall safety.

Fiberglass tanks are composed of fiber reinforcement embedded in a cured thermosetting resin, along with additives like dyes and pigments. These tanks are highly customizable, allowing for different combinations of glass fibers, resin, and designs to meet specific requirements. Known as fiberglass reinforced plastic (FRP), these tanks possess comparable strength to concrete.

Fiberglass reinforced thermosetting plastic, commonly known as fiberglass, emerged as a viable alternative to protected steel, stainless steel, and exotic materials in 1948. Its initial use in centrifugal cast fiberglass piping addressed corrosion issues in the crude oil production industry. Subsequent advancements in manufacturing techniques using polyester and epoxy resins during the mid-50s enabled the application of fiberglass tanks and piping in the chemical sector. By the mid-60s, fiberglass gained acceptance for storage and handling of underground flammable and combustible liquids, as well as industrial, municipal water, sewage, and pulp and paper processing. During the 1960s, manufacturers began developing nationally recognized standards and testing methods for fiberglass storage and piping systems. Today, there exists a comprehensive range of nationally recognized standards and specifications governing fiberglass tanks and piping.

General References for Fiberglass Reinforced Plastic Tanks

• API Specification 12P – Specification for Fiberglass Reinforced Plastic Tanks
• ASTM D3299 – Standard Specification for Filament-Wound Glass-Fiber-Reinforced Thermoset Resin Corrosion-Resistant Tanks
• ASTM D4097 – Standard Specification for Contact-Molded Glass-Fiber-Reinforced Thermoset Resin Corrosion-Resistant Tanks
• ASME RTP-1 – Reinforced Thermoset Plastic Corrosion Resistant Equipment
• AWWA D-120 – Thermosetting Fiberglass-Reinforced Plastic Tanks

FRP Tank Inspections

As per state or tank owner guidelines, a comprehensive inspection of both the interior and exterior surfaces of fiberglass tanks is typically required every 5 years. Various types of defects specific to fiberglass tanks are outlined in ASTM and RTP standards. Ensuring inspector safety is of utmost importance, particularly during internal inspections. Prior to inspection, proper safety measures must be taken to ensure the tank is clean and free from any chemicals, with acceptable air quality. Access to the FRP tank interior is achieved through either a ground-level or roof manhole. Special attention is given to the tank penetrations, carefully examining erosion, corrosion, mechanical damage, and any deterioration caused by environmental factors.

Despite their durability of up to 40 years, fiberglass tanks can experience damage due to various factors.

INTERVALS

EXTERNAL VISUAL EVALUATIONS:

In addition to applicable external inspection points associated with steel ASTs,  (read more here : https://ttienvinc.com/blog/aboveground-storage-tank-piping-pressure-vessel-inspections-when-and-what-exactly-is-required/) the exterior surface of the tank is thoroughly inspected. Along with the tank include areas such as ladders, handrails, mid rails, toe rails, flanges, nozzles, manway doors, pipes, pipe supports, and tank anchoring. Also inspect the tank supports/feet and tank support pad/floor supporting the tank for signs of corrosion and/or deformation.

We suggest a twice-a-year visual inspection to check for holes, corrosion, and other signs of wear and tear. Identify and document any:

• • UV Damage
  • Cracks
  • Crazing
  • De-Lamination/Peeling
  • Blisters or Bubbles
  • Physical Damage
  • Pimples
  • Pits (Surface)
  • Porosity (Surface)
  • Scratches
  • Topcoat Veil Deterioration

INTERNAL VISUAL EVALUATIONS:

Critical in evaluating the condition and fitness-for-service of FRP tanks include:

• • Chips
  • Cracks
  • Crazing
  • De-Lamination/Peeling
  • Blisters or Bubbles
  • Pimples
  • Pits (Surface)
  • Porosity (Surface)
  • Scrateches
  • Wrinkles