The Audit Commission (CA, from the Portuguese acronym) has released the performance audit report on the “Failure in the cable of the Taipa Line of Light Rail”, which aimed to investigate the incident of failure in the cable that forced the suspension of the light rail service in October 2021, as well as examining the standard and technical specifications initially adopted by the Transportation Infrastructure Office (GIT, from the Portuguese acronym), and the quality control in the inspection and acceptance of the cable.
GIT was dismissed in October 2019, so the documents which produced during the operation of GIT, was provided by the Public Works Bureau (DSOP, from the Portuguese acronym) for this audit. The Taipa Line, which cost 11 billion patacas, has started operation since 10 December 2019. The first failure of the cable occurred on 13 January 2020. After that, there were 18 times failure within two years, causing interruptions in the light rail service frequently, even with passengers being evacuated. Until 20 October 2021, it was decided to suspend the light rail service for more than five months, for replacing all of the cables of the Taipa line. These caught the public's attention and the relevant public sector should take serious attention to review the deficiencies, determine the responsibilities and follow up the issue rigorously.
The audit report stated that, based on the investigation and analysis reports, it was found that the direct cause of the failures of the cable was due to a wrinkle in the metallic screen, a defect that came from production technique, leading to the rupture of the screen after a certain time, and consequently causing the breakdown of the cable. On the other hand, the requirements of the technical specifications of the metallic screen were too low to effectively resist or reduce the problem of damage caused by its wrinkle, which consequently led to the rupture of the screen.
Regarding the control in the adoption of the standards and technical specifications, the public tender documents established that the cables must comply with the IEC 60502-2 standard (hereinafter referred to as “IEC standard”). Generally, the IEC standard establishes the minimum technical requirements for the structure of the cables. However, for the metallic screen which caused the incident, the IEC standard does not establish any detailed requirements, only stipulates that the material, size and wrapping method should comply with national regulations or standards. Thus, the detailed technical specifications could be defined by the supplier.
The supplier only proposed two categories of technical specifications for the metallic screen, namely the wrapping method and its thickness, which GIT accepted. However, the National Standards of the People's Republic of China(P.R.C.) (hereinafter referred to as the National Standards), issued by the General Administration of Quality Supervision, Inspection and Quarantine of the P.R.C. and the Standardization Administration of the P.R.C., defines three categories of technical specifications, namely the wrapping method, thickness and the metal annealing process. In other words, the specifications adopted by the supplier were significantly lower than those of the National Standards. As for examining how GIT analyzed and selected technical standards before inviting tenders, CA comprehensively reviewed all available documents, and found that there was no justification for selecting the IEC standard, and GIT did not conduct any horizontal analysis or comparison between mainstream standards, including the National Standards, to help the selection of appropriate standards of the cables. However, in addition to complying the minimum requirements of specified technical standards set out in the tender documents, the tenderers could also have other norms and standards as reference. To this end, attached to the tender documents and for reference purposes, was a list containing local regulations and international standards (including European and American ones), however, it did not include the National Standards.
Regarding the metallic screen, which was the main cause of the incidents, among the information obtained by CA, there was no document reflected that GIT had given overall consideration to the adoption of specified technical specifications(including the basis of adoption of specified technical specifications and the reference of mainstream standards which including the National Standards). Furthermore, regarding the diameter of the armor wires that forms part of the cable structure, the technical specifications adopted by the supplier did not comply with the minimum requirements clearly outlined in the IEC standard, revealing obvious omissions in the management of GIT. The audit report stated that, when choosing the technical standards to be applied to Macau's light rail, GIT should have taken into account the specific context in which Macau is located. The National Standards are more relatively in line with the reality of Macau, which have been practiced for many years, including in South China. Actually, the IEC standard does not formulate a mandatory specification for the metallic screen, but requires to comply with local regulations and standards.
Regarding the quality control of the cables supplied, the IEC standard determines that, before delivering the cables, the manufacturer must carry out type tests, to ensure the quality of the supplied cables are comply with the intended application. If there are changes to the components, design or manufacturing process, which may alter the characteristics of the cable, it is necessary to carry out a new type test again. The audit found that the metallic screen of the cables purchased for Macau’s light rail uses interval wrapping method, however, according to the final type test report, it showed that the metallic screen uses overlap wrapping method. The specifications of the two methods are completely different, and the supplier never submitted the type test report for the interval wrapping method, which does not comply with the IEC standard. During the process of examining and approving the type test report, the project consultant and GIT informed the supplier that the type of cable subject to testing did not correspond to the cable purchased. However, they did not follow up by urging the supplier to resubmit the type test report of the cable purchased for the light rail afterwards. Since the cable supplied did not correspond to the cable tested, it was not possible to know whether the supplier carried out the required tests on the type of cable that was used in the light rail system, and whether they were in compliance with the IEC standard.
However, when the third-party agency carried out its investigation of the incidents, it examined the items which selected in the type tests and found that the two items did not meet the requirements established in the IEC standard. The cable used in the light rail system, actually was installed without being subjected to tests as stipulated in the IEC standard (as stipulated in the supply contract) and without the corresponding certification, which reflects the obvious omissions in the management of GIT.
As mentioned in the general comments of the audit report, the execution of public works in Macau, besides the way of project outsourcing, they may also hire third-party agencies or experts to support, for providing professional services in project design, supervision and management. However, although the public sector has hired third party, it still has responsibility to establish reasonable supervision and control measures to ensure the outsourced public services are carried out properly. The audit results showed that the relevant public sector had some problems in the management of construction projects, including management and control in the hired third party. It should be noted that, even if the works has been outsourced or a third party has been hired to support, this does not mean that the responsibility of the public sector has ended. On the contrary, as the owner of public construction projects, the public sector is responsible for safeguarding the interests of the Macao SAR and must take appropriate corrective and regulatory measures.
The audit report was previously submitted to the Chief Executive, and the public can download the full text of the report from the website of the Audit Commission (https://www.ca.gov.mo), while paper copies are available at its Office during office hours.
