Documentação Técnica

Documentação Técnica
* Engenharia de Dragagem, Sinalização Náutica, Batimetria, Projetos de Canais Navegáveis, Meio Ambiente, Cartas Náuticas, Software de Navegação, Topografia Básica e outros assuntos técnicos.

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terça-feira, 14 de junho de 2011

AIDS TO NAVIGATION: OBJECTIVES OF REMOTE MONITORING AND CONTROL

When considering a remote monitoring and control system it is necessary to identify the purpose and use of the system. Questions which arise include, why monitor, what aids and systems should be monitored, what communications should be used, what records should be kept, etc.

The typical operational goal of an Aid to Navigation (AtoN) is to provide a requisite availability of service and reduce as much as possible any down time. Availability is inversely proportional to the Mean Time Between Failures (MTBF) and the Mean Time to Repair (MTTR). Both MTBF and MTTR should be reduced as far as possible. When planning his passage the mariner anticipates that the AtoN on his route will be functioning in accordance with the published characteristics laid down in nautical documentation and on charts. In the interests of safety the mariner should be notified as soon as possible of any failures of AtoN. A minimum Time to Detect is therefore necessary. The availability of the AtoN can be maintained by identifying faults which reduce redundancy. AtoN availability can be affected by both the AtoN system redundancy and by support systems such as power systems, which must therefore be considered. Similarly, security, intruder and flood alarm systems must be considered because of the threat such events may pose to the AtoN. The cost effectiveness of the AtoN service should be maximised with the provision of remote monitoring and control.

The objectives of a remote monitoring and control system may vary depending on the policies of the administration, the type and importance of the AtoN being monitored, and the local conditions. The designer of a remote monitoring and control system may not need to include all of the following objectives and will only select those which best suit the application.

- Provide information to the operator consistent with his level of competence.
- Provide controls to the operator consistent with his level of competence.
- Monitoring and control system reliability and availability must be comparable with the systems being monitored.

Identification of Failures (affecting AtoN system provider liability)

- Identify failure of AtoN to operate within published specification.
- Notify failure of AtoN within a time period consistent with the phase of the voyage in which the aid is used and the criticality of the aid for safe navigation.
- Compile and maintain a record of operation of AtoN.

AtoN Availability

- Confirm operation of AtoN within specification.
- Identify faults which reduce redundancy and which therefore threaten the AtoN.
- Notify faults within a time period necessary to carry out repairs before failure of the redundant stand-by system.
- Reduce downtime and improve availability through use of remote control resets.
- Verify status of redundant systems through remote control testing.

AtoN Maintenance (affecting MTBF and MTTR)

- Reduce downtime through use of remote control resets.
- Testing of redundant systems using remote control testing.
- Reduce incidence of faults through identification of recurring faults using post mission analysis.
- Assist investigation of cause of faults and failures using additional monitored parameters.
- Assist investigation of cause of faults and failures using historical data.

AtoN Cost Reduction (affecting cost of providing AtoN service

- Reduce maintenance visits through use of remote control resets.
- Reduce maintenance visits by testing of redundant systems using remote control testing.
- Reduce costs through identification of recurring faults using post mission analysis.

AIDS TO NAVIGATION TO BE REMOTELY MONITORED

In general, the providers of AtoN monitor the operation by one of the methods described in Section 2 (Methods Of Monitoring).

A decision must be made as to which aids merit the extra security offered by remote monitoring and control described in section 3. Typically the decision is strongly determined by the relative importance of the aid in the waterway aid system.

The AtoN facilities for which monitoring should be considered fall into the categories detailed below.

Fixed Aids

Major lighthouses and Stations are frequently remotely monitored. When doing so, all AtoN signals should be monitored. These will include the main light, standby light, emergency light, sector light and fog signals where fitted. Radio aids to navigation which include radiobeacons, with or without DGPS, and racons should also be monitored. In addition, the ancillary equipment such as power supplies, intruder alarms, fire fighting and detection equipment should be monitored.

Minor lights are rarely remotely monitored, but the Operating Authority sometimes elects to do so for a critically important aid.

Sector lights. Depending on the complexity of the aid and its importance in the waterway, consideration should be given to monitoring sector lights.

Leading lights. Depending on the complexity of the aid and its importance in the waterway, consideration should be given to monitoring leading lights.

Floating Aids

Lightvessels. All AtoN signals should be monitored. These will be similar to those fitted to major lighthouses with the exception of radiobeacons and sector lights. Additional ancillary equipment may be fitted such as collision monitors and position tracking systems. The output of the latter may be used to operate off station and riding lights. Alternatively, a remote control may be provided for this function.

Lanbys and Lightfloats may contain AtoN similar to those fitted to lightvessels and should be monitored.

Major buoys fitted with a light, racon and a position tracking system should be considered for remote monitoring.

Other navigational buoys are rarely remotely monitored, but the Operating Authority sometimes elects to do so for a critically important aid.

Offshore Structures

Offshore structures comprising oil and gas rigs have their AtoN approved by the Authority, but are generally monitored by the operator of the structure.

Fonte: Diretoria de Hidrografia e Navegação, IALA.

NOTA DO EDITOR

O texto acima é suficientemente claro - não adianta possuir qualquer sistema de monitoramento de sinais náuticos se, a partir de informações sobre falhas no balizamento, não existirem ações concretas de restabelecimento da sinalização.

O problema da sinalização náutica das hidrovias gaúchas não é a falta de informações sobre a posição dos sinais náuticos, nem sobre outras discrepâncias. O site da Praticagem da Lagoa dos Patos, cujos pilotos circulam diariamente nos canais de navegação, proporciona tais informações no espaço "Monitoramento dos Sinais".

Por outro lado, a Marinha do Brasil realiza o monitoramento e controle desses sinais, com freqüência quinzenal, publicando e notificando a SPH sobre as discrepâncias encontradas no balizamento sob sua responsabilidade. Além disso, é comum os navegadores em geral forneceram informações sobre tais problemas, inclusive indicando a posição de sinais desaparecidos.

Apesar disso, é comum a ausência de qualquer ação de restabelecimento por períodos de vários meses, durante os quais os sinais continuam apagados, desaparecidos ou fora de posição. Quer dizer, o grande problema é o "Mean Time to Repair" (MTTR), inadmissível (a rigor não está sendo feito quase nada). A solução é muito simples - colocar as embarcações e o pessoal na água, com os equipamentos e materiais necessários, e restabelecer os sinais náuticos apagados, reposicionar os que estão fora de posição e resgatar/substituir os desaparecidos. Vale dizer, fazer o tema de casa.

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