5/8”BS 4825 1.4404 (AISI 316L) Sanitary Butt Weld long tee

BS 4825 long Welded Tee

Dimensions & Sizes

Core Principles of BS 4825 for Sanitary Fittings

BS 4825 is the authoritative British Standard for stainless steel piping systems in the food, dairy, and pharmaceutical industries. It covers the dimensions, materials, manufacturing, and surface finish requirements for sanitary fittings, with its core design philosophy being to ensure a system free of dead legs, easy to clean and sterilize thoroughly, meeting stringent hygienic production specifications.

Material and Manufacturing Requirements

The standard requires fittings to be made of austenitic stainless steel, such as AISI 316L (1.4404) or AISI 304 (1.4301), with chemical composition and mechanical properties complying with European material standards (e.g., EN 10357). All welds must be fully penetrated, continuous, and uniform. Discoloration must be removed post-welding, and the weld must be polished to the same finish as the base material.

Dimensions and Tolerances

BS 4825 strictly defines tolerances for outside diameter, wall thickness, and bend radii of fittings. For instance, the centerline bend radius of an elbow must match the pipe diameter (typically 1-1.5 times the diameter) to ensure smooth fluid flow and avoid stagnation. Dimensional tolerances must guarantee complete internal alignment after welding, forming a smooth transition.

Surface Finish and Hygienic Design

All product contact surfaces must be mechanically or electropolished, with a typical internal surface roughness of Ra ≤ 0.8 µm. The internal design must follow the no-dead-leg principle, with all corners having smooth transitions (radius ≥6mm), and no concavity or crevices at welded joints.

Connections and Testing Certification

The standard supports both butt-weld and clamp connections. Butt-weld fittings require beveled ends to ensure flush internal alignment post-welding. Products must pass pressure tests and visual inspections, and provide material certificates conforming to EN 10204 3.1, ensuring full traceability from raw material to finished product.

International Compliance

Fittings compliant with BS 4825 meet the EU Pressure Equipment Directive and UK Food Contact Material Regulations, making them suitable for global sanitary system integration.