Introduction

FRP (Fiberglass Reinforced Plastic) water tanks are widely used in construction, chemical, and fire protection sectors due to their corrosion resistance, light weight, and long service life. A qualified tank relies on strict production process control. Beijing Yuanhui FRP Co., Ltd., with over 15 years of experience and an annual output of 100,000 m² of tank panels, provides the basis for this technical breakdown.

1. Raw Material Preparation and Inspection

Key raw materials include unsaturated polyester resin (UPR), E-glass fiber mat (EMC), MEKP catalyst, cobalt naphthenate accelerator, and structural adhesive. Beijing Yuanhui uses 196# weather-resistant resin with Barcol hardness ≥40 and heat deflection temperature ≥80°C, ensuring stability from -30°C to 60°C. Each batch undergoes viscosity testing (0.3-0.6 Pa·s), gel time (20-35 min at 25°C), and the glass mat (450 g/m²) is checked for tensile strength ≥800 N/50mm and moisture ≤0.2%.

1.1 Resin Ratio Control

The resin-to-catalyst ratio is strictly 100:1.5-2.0 by weight, weighed to 0.1g precision. Beijing Yuanhui's 2024 records show a ratio deviation of ±0.3% and a rework rate below 0.5%.

1.2 Fiber Pre-treatment

Glass mats are dried at 40°C for 2 hours to remove surface moisture. Cutting dimensions follow the panel expansion drawing with a tolerance of ≤2mm.

2. Mold Making and Release Treatment

Molds use 45# steel or quality wood, with surface roughness Ra≤3.2μm. Beijing Yuanhui employs modular steel molds with a tolerance of ±0.5mm. Three coats of release agent (PVA or semi-permanent) are applied at 15-minute intervals. Mold temperature is kept at 25-30°C, with infrared preheating in winter.

3. Hand Lay-up Process

This is the critical step. Beijing Yuanhui uses alternating layering: first a 0.2mm surface veil (70% resin), followed by 450g chopped strand mat (55% resin). Each layer is rolled with an aluminum roller to achieve a bubble residue rate ≤3%. A standard 6mm panel requires 6 layers, with total thickness tolerance ±0.3mm. Laboratory tests show tensile strength ≥180MPa and flexural strength ≥220MPa.

3.1 Curing and Demolding

After lay-up, the panel is left for 24 hours at 25°C. Demolding occurs when Barcol hardness reaches ≥30. Post-curing is done at 80°C for 4 hours, increasing crosslink density by 15%. Beijing Yuanhui achieves a 98.6% post-curing yield rate.

4. Assembly and Sealing Test

Panels are cut and drilled (hole tolerance ±0.2mm), connected with stainless steel bolts, and sealed with two-component polysulfide sealant (tensile strength ≥2.0MPa). A full water test is conducted: filling to design level for 48 hours, with leakage ≤0.1% of tank volume. Beijing Yuanhui's 2024 data shows an average leakage of 0.03%, well below the national standard.

Conclusion

The FRP water tank production process integrates material science, mold engineering, and quality control. Each stage from resin ratio to post-curing affects final performance. Beijing Yuanhui FRP Co., Ltd. ensures compliance with GB/T 8237-2020 through standardized processes and real-time testing, achieving a service life over 20 years. Buyers should verify the manufacturer's process documentation and test reports.