FRP/GRP Water & Chemical Storage Tanks Manufacturing Process
Glass Reinforced Plastic (GRP) or Fiberglass Reinforced Plastic (FRP) storage tanks are widely used in the chemical industry for their high corrosion resistance, lightweight structure, and durability. The manufacturing process of these tanks, particularly using filament winding machines, is a precise and sophisticated procedure. Below is a breakdown of the steps involved:
1. Material Preparation
Fiberglass Roving
This is a continuous strand of fiberglass that provides structural strength to the tank. It is often treated with a resin-compatible coating.
Resin
Epoxy, vinyl ester, or polyester resins are commonly used. The resin acts as a bonding material and enhances corrosion resistance. Additives like hardeners or curing agents are also prepared.
2. Mandrel Preparation
A mandrel, or mold, is the cylindrical form around which the fiberglass is wound. The mandrel can be metallic, collapsible, or removable and is usually designed to the required dimensions of the tank.
- The surface of the mandrel is cleaned.
- A release agent is applied to prevent the tank from sticking to the mandrel after curing.
3. Filament Winding Process
The filament winding machine is programmed with the desired winding pattern and specifications, such as helical or hoop winding angles.
- Fiberglass rovings are fed through a resin bath where they are impregnated with resin.
- The resin-soaked rovings are then wound around the rotating mandrel in specific orientations.
Winding Patterns
- Helical Winding: Fibers are wound at a helical angle to provide strength against axial stresses.
- Hoop Winding: Fibers are wound perpendicular to the mandrel’s axis, providing strength against hoop stresses (internal pressure).
The machine may use both helical and hoop winding in layers to achieve the optimal strength and design specifications.
4. Curing
Once the winding process is complete, the tank is left on the mandrel to cure.
- Curing may take place at room temperature, or for faster curing, the tank may be heated.
- The curing process solidifies the resin, bonding the fiberglass layers into a rigid and strong structure.
5. Mandrel Removal
After curing, the tank is separated from the mandrel. For a collapsible or removable mandrel, it is dismantled or carefully removed.
- If the mandrel was fixed, the tank may be cut open slightly to facilitate removal, and any cuts are then sealed or patched.
6. Finishing and Quality Control
- Edges and any imperfections are trimmed or sanded.
- The tank undergoes quality control checks, including thickness measurement, leak testing, and structural integrity assessments to ensure it meets the required specifications.
7. Testing and Final Inspection
Tanks are pressure tested and inspected for leaks or structural weaknesses. This may include hydrostatic testing or other methods depending on the intended use.
A final quality check ensures the tank’s readiness for use in chemical storage applications.
Summary
The filament winding process is ideal for GRP/FRP tanks due to its precision and ability to customize the thickness and pattern to the required strength standards. This manufacturing method results in a highly durable and corrosion-resistant tank suitable for chemical storage.