Evacuated glass tube

Buyers should prioritize Borosilicate Glass 3.3, which offers superior thermal shock resistance and mechanical strength. The absorption rate should be ≥94%, while the emittance should be ≤6% to ensure maximum heat retention. Pay close attention to the vacuum degree (P ≤ 5.0 × 10⁻³ Pa), as this determines the insulation efficiency. Additionally, verify the coating type, such as AL-N/AL or the more advanced SS-CU-ALN/AIN three-target coating, which provides better performance in low-light conditions.

Request test reports for hail resistance, ensuring the tubes can withstand impacts from ice balls of at least 25mm in diameter. Check for thermal stagnation temperature ratings; high-quality tubes should reach over 200°C without degradation. It is also essential to confirm ISO 9806 or Solar Keymark certification for international quality assurance. For long-term reliability, ensure the supplier uses a high-quality getter to maintain the vacuum over a 15-20 year lifespan.

Evacuated tubes are primarily used in Solar Water Heaters (SWH), industrial process heating, and solar cooling systems. When sourcing, ensure the tube dimensions (typically 47mm x 1500mm or 58mm x 1800mm) are compatible with your existing manifolds or tank frames. If you are purchasing heat pipe evacuated tubes, verify the condenser diameter (14mm or 24mm) to ensure a proper fit into the heat exchanger.

Glass tubes are highly fragile. You must mandate export-standard five-layer corrugated boxes with EPS (Expanded Polystyrene) foam inserts for each tube. For bulk sea freight, require palletization with shrink wrap and corner protectors. It is highly recommended to negotiate a breakage allowance (usually 1-3%) or ensure the supplier provides extra units (spares) free of charge within the container to cover potential transit damage.

When using Made-in-China.com, look for Audited Suppliers with verified production lines. Negotiate based on Total Cost of Ownership (TCO) rather than just the unit price; ask for a breakdown of packaging, loading, and inland trucking fees. For first-time buyers, use Secured Trading Services to protect your payment until the goods are shipped and inspected. Always request a Proforma Invoice (PI) that explicitly states the vacuum warranty period (typically 5-10 years).

Ensure the supplier provides the correct HS Code (typically 7017.90 or 8419.90) to avoid customs delays. Because these items are bulky but relatively light, Full Container Load (FCL) is much safer and more cost-effective than Less than Container Load (LCL), as it reduces manual handling. For shipping to regions with strict trade policies, verify if there are anti-dumping duties on Chinese glass products and ensure all Certificate of Origin documents are prepared to leverage applicable trade agreements.