Incidents

	Near-miss in a HPDE-unit in Belgium		PDF
	This document is supplied by kind permission of the Belgium Competent Authority.It describes an "accident near miss" from which we can all learn. The incident occurred in an HDPE unit following an electrical power failure and subsequent shut-down of the unit. Upon start-up it was discovered that a large crack covering over a third of the circumference of one of the reactor flanges had developed. The report describes the investigations into the cause of the fracture and draws conclusions and recommendations so as to prevent a similar occurrence. The main conclusions of this research are: An annealing of normalising heat treatment of such flanges is absolutely necessary in order to limit the risk for brittle fracture. It should be compulsory irrespective of size and rating class of the flange. In ASTM A 105 a treatment is only mandatory for flanges above ANSI Class 300. The certificate of the manufacturer is not very reliable as to the heat treatment. 5 of the 20 investigated flanges had clearly not been submitted to a proper heat treatment, although the certificate said so. This problem seems not to be limited to ASTM A 105 and shows the need for the evaluation by the user of the capability and reliability of the manufacturer. The quality and integrity of all flanges in use, which can be exposed to temperatures below 0°C and where failure can have serious consequences, should be evaluated. These conclusions have been represented and discussed with industry and independent controlling bodies (notified bodies) in September 2002. As a result, all Belgian Seveso-companies have been asked to evaluate their flanges in use according to the procedure explained in the brochure and to adapt their internal standards.		ASTM_A_105.pdf 86 KB

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