TECHNICAL
AS 1528:2019 A NEW EDITION PITCHED AT FOOD SAFETY, CONSISTENCY, USEABILITY AND CURRENT PRACTICE
The aim of AS 1528: Stainless steel tubes and tube fittings for food processing and hygienic applications is to standardise hygienic tube and fittings for use in dairy, food and beverage manufacturing. It has been successful in maintaining the required food safety standards in Australia and New Zealand.
AS 1528 was first issued in 2001 and developed by an ASSDA group of stakeholders in the manufacture, supply, fabrication and use of stainless steel tube and associated fittings in the food manufacturing industries. Changing industry practice, some existing errors, internal consistencies and expansion of sizes required a revision of the standard. The drafting journey to bring AS 1528 up-to-date began in 2015 and has been a challenge, but its successful outcome is significant for the industry and a testament to everyone involved. The new edition of AS 1528 was published in four parts by Standards Australia in October 2019: Part 1
Tubes
Part 2
Screwed tube couplings
Part 3
Butt weld tube fittings
Part 4
Clamp tube fittings
The revision of the AS 1528 suite of standards from the 2001 edition has brought the documents’ technical coverage up to current practice and recognised the target industries in which hygienic tube is used. The suite is easier to understand and use, and facilitates verification of product compliance so that it achieves the required hygienic conditions.
6 – Australian Stainless Issue 68
What the revision achieved The 2019 edition achieved all of the original aims, except one (see below). The suite of four standards now presents as a consistent coverage of all the tube and fittings regularly supplied in Australia. 1. Addition of a consistent set of pressure ratings across all parts of AS 1528. Useful for designers. 2. The wall thickness tolerance for tube has been changed. Previously it was +nil/-0.10mm for all sizes of tube. Widening it out to ±10% brings it into line with most other tube specifications and makes it more economical to manufacture without compromising product quality. It also then matches the tolerances of the fittings in other parts. 3. The title now includes ‘hygienic applications’ in addition to food processing. This recognises the wider range of applications in which these products are already used. 4. The reference to duplex stainless steels has been removed. In practice all tube and fittings referenced by these standards are austenitic. 5. All tube and fittings can be produced without grit polishing the internal surface. Internal surface finish is specified by measurable roughness for hygiene and cleanability. 6. Inner tube surface roughness has been set as 0.8µm Ra maximum; this is consistent across all four parts of the standard and is also consistent with US and European specifications. From a cleanability perspective this is adequate. In addition there is now a specified maximum roughness for the inner weld bead, specified as ‘Rt’. This is an unusual specification but it does address directly the requirement for cleanability of the remnant weld line. 7. For the first time there is a stated limit for inner weld surface heat tint (no more than Level 3 in AWS D18.1M, commonly referred to as ‘pale straw’). Again this aligns with US and European standards and much research work promoted by ASSDA and others.
