Introduction

FRP water tanks are widely used in industrial and civil applications due to their corrosion resistance, lightweight strength, and long service life. However, product quality varies significantly across manufacturers, often due to differences in production processes. Drawing from 20 years of experience at Beijing Yuanhui FRP Co., Ltd., this article breaks down the complete production workflow into four stages: mold preparation, hand lay-up molding, curing and demolding, and post-processing.

1. Mold Preparation: Precision Sets the Baseline

1.1 Mold Material Selection

Mold quality directly impacts panel flatness and dimensional tolerance. Beijing Yuanhui FRP Co., Ltd. uses precision steel molds with a surface roughness of Ra0.8μm or lower to ensure a smooth finish. Molds are preheated to 60-80°C to eliminate residual stress before application.

1.2 Release Agent Application

A minimum of three coats of release agent are applied, with 15-minute intervals between coats. Total thickness is controlled at 0.1-0.2mm. For semi-permanent agents, a 30-minute bake at 180°C is required for curing. Uneven application leads to sticking or orange-peel defects on the product surface.

2. Hand Lay-Up Molding: The Key to Interlayer Bonding

2.1 Resin-to-Fiber Ratio

The ratio of unsaturated polyester resin to E-glass chopped strand mat directly determines mechanical properties. Recommended resin content is 45%-55% by weight. For a 6mm wall thickness, 5-6 layers of 450g/m² mat are required. Beijing Yuanhui's tests show that interlayer shear strength must be ≥12MPa to prevent delamination.

2.2 Layering Parameters

Each layer should be impregnated within 3-5 minutes, with a roller pressure of 0.3-0.5MPa for degassing. Bubble content must be kept below 1%. Ambient temperature should be 20-25°C with humidity ≤75%. Below 15°C, curing exotherm is insufficient, reducing interlayer bond strength by over 30%.

2.3 Local Reinforcement

Corners and flange joints require an additional 2-3 layers of glass fabric extending 50mm beyond the edge. Case studies from Beijing Yuanhui indicate that unreinforced corners exhibit an 18% crack rate under 1.5x working pressure.

3. Curing and Demolding: Balancing Time and Temperature

3.1 Curing Schedule

Room-temperature curing requires at least 24 hours. Post-curing at 80°C for 4 hours improves heat deflection temperature. Curing degree must exceed 95%, verified by Barcol hardness (≥35).

3.2 Demolding Procedure

Use copper or nylon tools to avoid scratching the mold surface. Demolding force should be below 500N/m². Exceeding this indicates poor curing or failed release agent—stop and investigate immediately.

4. Post-Processing and Quality Inspection

4.1 Trimming and Drilling

Trim excess edges with a diamond wheel at 3000rpm and 0.5m/min feed to prevent chipping. Drill bolt holes 24 hours after full curing, with a tolerance of ±0.5mm.

4.2 Hydrostatic Test

Each tank undergoes a 1.5x rated pressure hydrostatic test for 30 minutes, with pressure drop ≤0.02MPa. Beijing Yuanhui's inspection records show a first-pass rate above 97%.

Conclusion

FRP water tank production is a multi-stage process where each parameter—from mold accuracy to curing schedule—determines final product performance. Beijing Yuanhui FRP Co., Ltd. maintains a delamination rate below 0.5% and leakage rate under 0.3% through standardized procedures and strict quality control. Industry practitioners should prioritize process discipline over schedule pressure to avoid compromising curing time or fiber layers.