[ Super Duplex ]
[ Super Duplex ]
By testing pipe samples , with machined and un-machined surfaces , creviced using polyacetal washers , specially machined to suit the curvature of the pipes being used , we have found that skim machining of the sealing face significantly increases the RCCT of the connection ( Figure 5 ). These results don ’ t relate directly to the performance limits of the mechanical joint , but they do show the benefit of the machining operation . Our company now machines the sealing face connections as standard ( Figure 6 ). Subsequent , long-term , experience in Middle East conditions ( 4 ) supports the testing results . To work well , these alloys must be properly manufactured , fabricated , and installed . Sophisticated users , like the oil and gas industry , are very aware of this ( 5 ) . We recommend that similar disciplines be adopted by the desalination industry ( 6 ) .
References
1 ) Johan Nordström ,“ Stainless Steel for High Pressure Piping in SWRO Plants . Are there any Options ?” ACOM No . 3 -95
2 ) JW Oldfield ,“ Crevice Corrosion of Stainless Steels II Experimental Studies ”. British Corrosion Journal . Volume 13 , No . 3 . 1978 .
3 ) JW Oldfield “ Test Techniques for the Pitting and Crevice Corrosion Resistance of Stainless Steels and Nickel Alloys in Chloride Environments ”. International Material Reviews . Vol 32 . No . 3 . 1987 .
4 ) R Howard ,“ Improving Manufacturing Quality of Duplex Stainless Steel Components ”. Proc Conf Duplex Stainless Steels . Paper III . C . I Beaune , France , October 13 to 15th , 2010
5 ) G Byrne “ The Use of ZERON 100 Super Duplex Stainless Steels in High Pressure ( HP ) Seawater Feed and Brine Reject Pipework in Sea Water Reverse Osmosis ( SWRO ) Plants in the Middle East . Proc . Conf . NACE UAE . Abu Dhabi . Jan 2019 .
6 ) G . Byrne “ Specifying and Securing Quality in Procurement , Manufacture and Fabrication of Duplex and Super Duplex Stainless Steel Parts for Sea Water Reverse Osmosis ( SWRO ) Applications ”. Proc . Conf International Desalination Association World . Dubai . UAE . 201
Summary and conclusions SDSS are now the alloys of choice for HPSF and BR pipework systems in SWRO plants . This is because these alloys are the most commercially attractive solution that provides the necessary corrosion resistance in the most severe SWRO conditions . However , the continued successful application of these grades requires the engineering contractors to apply a disciplined approach to manufacturer selection , product specification and quality , fabrication and installation processes and procedures .
Acknowledgements I would like to thank the directors and shareholders of Rolled Alloys for permission to publish . I would also like to acknowledge the contributions of Dr Roger Francis and Mr Geoff Warburton .
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