The Institute of Refrigeration and British Refrigeration Association have collaborated in producing new guidance following a proposal to introduce new design stress values for copper tube in the European Standard EN14276.
Explaining the new proposal, Gordon Adams, technical manager at Climate Center, who played a key role in the revision said: “The result is an increase in the maximum allowable pressure (PS) for equivalent thicknesses of copper tube, which will create a level playing field for the industry across Europe.
“The revised guidance incorporates new design stress values for copper tube, which were not included in the original European standard. A recent amendment, however, has proposed that stress values be included in a future review of the standard, opening the way for a review here in the UK.”
Following some detailed development work and discussion by relevant industry committees, it has been agreed that this new approach can now be applied in the UK.
The changes, which have taken two years to implement, have implications for a number of key standards and practices used in the UK refrigeration and air conditioning industry.
For example, the strength pressure test required on copper tube under the Safety Standard BS EN378 has been clarified, and now allows – subject to certain conditions being met – for the test to be carried out at 1.1x the maximum allowable pressure.
The main change from the existing BS1306 standard to the European Standard EN14276 is a reduction in the safety factor, allowing the use of increased pressures for tube with the same wall thickness.
“It had been recognised for some time that the British Standard was very conservative,” said Gordon Adams. “The revised guidance gives more latitude, allowing a stress value at 150C to be used for discharge lines.”
The new guidance gives clear tables for the maximum allowable pressure of copper tube for the common diameters and wall thicknesses. It also highlights the minimum design pressures for commonly used refrigerants, bringing key information into a single reference point.
Gordon Adams says: “Given the importance of the guidance for the safety and reliability of plant, we have gone through the data underlying the proposed changes extremely thoroughly. The key thing was to get it right, and ensure the industry could proceed to use the new approach with confidence.”
He added: “I would like to thank my colleagues from both the IOR and BRA, who have worked closely to evaluate and agree the changes.”
The guidance, Selecting copper tube and fittings, Institute of Refrigeration Guidance Note 25, is available from www.ior.org.uk