Maintenance of equipment

Throughout the life of the tunnel, the operator should carry out both the maintenance of civil engineering works and the tunnel equipment. (See Report 05.13BEN "Good Practice for the Opereation and Maintenance of Roads Tunnels"). The maintenance of civil engineering structures is not described in this paragraph.

The maintenance operations on equipment can be classified into two groups:

• Preventive measures that are carried out at fixed intervals with the objective of maintaining the equipment in a good operating condition. Preventive maintenance offers the advantage of preventing, as far as possible, unforeseeable failures and is easy to plan in advance. It can however lead to high costs if the interventions are too frequent. They therefore need to be suitably optimised. There are two kinds of preventive maintenance: systematic maintenance and predictive maintenance.
• Corrective actions that are carried out when a system or a part of a system has failed or been damaged. Corrective maintenance offers the advantage of using a system to the maximum extent of its service life. Its disadvantage however, is that it cannot be planned and therefore emergency repairs are normally carried out with a significant surplus cost and consequences for the traffic flow.

It is recommended to use preventive maintenance where possible and for those systems that are not redundant and are related to safety. Preventive maintenance allows the joint planning of different maintenance tasks in the event of every closure of the tunnel to traffic. Moreover, it helps maintain the equipment in a good operating condition. It may be noted however that even when preventive maintenance is carried out very well, the operator cannot avoid corrective interventions. However, preventive maintenance will ensure costly corrective maintenance is kept to a minimum.

Usually the operator's staff do not carry out all maintenance tasks; the operator normally entrusts contractors and several options are consequently available:

• It is possible to contract only those maintenance tasks related to a specific technical level. The operator can thus contract tasks that present no technical complexity (cleaning, washing, ...) or it can contract only very complex tasks (supervision system, radio retransmission equipment, ...)
• It is possible to contract all tasks of one or more equipment groups (all ventilation systems, all remote surveillance installations, etc.).

Chapter 7 of Technical Report 05.06.B entitled "Cost of maintenance", chapter 4 of Technical report 05.13.B entitled "Maintenance and operation" and chapter 6 of Technical Report 2007R04 entitled "Organising operating staff", give more complete information on the subject of maintenance.

If they exceed a few hundred meters in length, road tunnels are to be provided with equipment for ensuring the safety of users under normal conditions or in case of disruptions to normal operation. Because of their involvement in the global safety chain of the tunnel, this equipment must be selected and designed with great care, with regard to maintenance, inspection and refurbishment. Hence a report has been produced to assist the operator or operating body with the issue of maintenance and technical inspection.

The technical report 2012R12EN entitled "Recommendations on management of maintenance and technical inspection of road tunnels" gives recommendations for the management of maintenance, essentially in the domain of equipment. The aspects relating to light civil engineering are listed and described only very briefly.

Life Cycle Cost (LCC) aspects have become an important issue for private tunnel owners, as well as government agencies. Sound knowledge of life cycles helps to optimise investment costs during the early stages of designing a system. It is also helpful in organizing the periodical maintenance of technical equipment. The technical report 2012R14EN entitled "Life cycle aspects of electrical road tunnel equipment" outlines how LCC aspects support the design of equipment as well as maintenance concepts. Bearing in mind that investment decisions are often technology-driven and that equipment costs have risen dramatically in the past years, the report helps to understand the life cycle process and the aging process of material. The report provides background knowledge on LCC aspects, which could be of use for further investigations. Specific focus is given to the surrounding ambient conditions, e.g. temperatures, which have a significant impact on the aging process.