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La revue soGaz #4
Gas in Focus - 2019 edition
Le Gaz. L'Énergie des Possibles. - 10 new reports to discover

Works

GRTgaz intervenes regularly on its network to do maintenance operations.
That can involve unavailabilities of capacities for shippers customers. Find in this part the provisional works programme as well as the description of the works carried out.

  • The program (for information purposes)

    Publication of the maintenance works program
    The reference works program drawn up in March of year n represents a commitment by GRTgaz to its customers.

    The program may still be amended up to two months before the date of the works and the reduction level may change up until D-5 before the date of the considered works.

    Each shipper has day-by-day access to the corresponding reductions via his TRANS@ctions portal. The maintenance schedule is also on Smart GRTgaz. This information is updated on a daily basis.

    Works and their impact on the operational capacity [new]


    The provisional works programme for the following year
    Before the official March publication of the works programme for a given year, GRTgaz publishes a general outline of the programme in October and then again in December of the preceding year. This publication is sent out by e-mail and is for illustrative purposes only. It allows you to plan ahead and prepare your programmes for the following year.

    The program is downloadable as information below:

    GRTgaz vous propose plusieurs fichiers d’aide à l’utilisation du programme travaux :

    2020 Maintenance Webinar


    Reminder:

    Only the restrictions published on TRANS@ctions (CMNTt-CPRTt) are contractual values.

  • How will the maintenance policy be reflected in the maintenance works program?

    The maintenance policy will cause capacity reductions. These will be notified to customers by means of an annual maintenance works program.

    The works program for year n will consist of:

    • testing and checks on proper operation,
    • the annual part of the system inspection program,
    • an estimatation of the repairs to be addressed immediately following the inspections for year n,
    • planned repairs following the inspections for year n-1,
    • connection operations for new facilities.
  • What are the main deadlines for the maintenance works schedule? (indicative calendar)

    Main deadlines for the maintenance works schedule

    Shipper survey on forecasts

    This survey is used to check the compatibility of the scheduled works with the expected flows on the transmission system and the replenishment of storage reservoirs for the following winter.

    The quality of the replies from the shippers is thus critical as it will directly influence the works scheduling choices made by the GRTgaz teams.

  • What kind of maintenance works is GRTgaz carrying out on its transmission system?

    There are three major types of works:

    • Preventive maintenance (testing, inspection, etc.),
    • Repair works (depending on inspection results or following damage to facilities by a third party, for example),
    • Actions intended to increase future capacity (for example new facilities or the connection of new facilities to the existing system).

     

     

  • Why is GRTgaz inspecting its transmission system?

    The maintenance policy of GRTgaz is intended to:

    • ensure the safety of people and property and protect the environment,
    • ensure the availability and reliability of facilities,
    • ensure that facilities are fully controlled over time,
    • implement the legal requirements. The New Safety Regulations (NRS) of August 4, 2006 specify the methods to be used to verify the suitability for service of pipelines. Verification of the entire system is to be carried out over a 10-year cycle.

    This policy is to be implemented via:

    • a preventive maintenance plan (monitoring of works by third parties, checks on proper operation, etc.),
    • an inspection program for the entire transmission system, i.e. approximately 32,000 km of pipelines. The purpose of this program is to detect and repair faults that may affect the service suitability of pipelines. New inspections will then be scheduled to ensure continuous monitoring of the transmission system status.

    New works are treated according to the same principles: an initial inspection will be organised to check that they have been completed in compliance with the GRTgaz expectations as regards safety and pressure resistance.

  • How are the pipelines in the GRTgaz system inspected?

    The inspections are carried out by means of:

    • Above-ground electrical measurements to detect faults in the pipeline coating from the ground surface without unearthing the pipes, or
    • instrumented pigs travelling through the pipelines that can directly locate, identify and determine the size of pipeline faults.

    Following diagnosis, the relevant section can be excavated to confirm and repair the fault.

    The main types of instrumented pigs are:

    • Instrumented pigs for geometrical testing. These tools are used to detect variations in pipe diameters (changes in pipeline categories, reductions, dents, out-of-roundness, etc.). The technologies used for the pigs are based mainly on mechanical or electromagnetic devices.
    • Instrumented pigs used to detect metal losses. These detect corrosion and scratches. In general, instrumented pigs that detect metal losses via magnetic flux leakage (MFL) are the most widely used tools. The principle consists of generating a strong magnetic field in the wall of the pipeline using permanent magnets or electromagnets and then measuring the density of the magnetic flux "escaping" from the wall where thickness problems are present.

    Above-ground electrical measurements involve the following operations:

    • determining the corrosion risk areas based on an analysis of the risk factors,
    • step-by-step searching for coating defects in these areas,
    • selecting and carrying out the necessary earthwork,
    • assessing the damage to the coating and any damage to the metal.
  • What are the principles governing the diagnosis and repair of faults?

    Diagnosis and repair are based on rules collected in a public document, the ARD (Analysis and Repair of Defects) Code, which has been authorised for use by the administrative authorities.

    The code covers the following main methodologies:

    • validation of the fault analysis criteria,
    • qualification of the repair techniques,
    • operational implementation of the analysis criteria and the fault repair techniques.

    All faults and defects are systematically defined and their sizes are compared with the corresponding analysis criteria in order to determine their acceptability.

  • What are the fault repair techniques used by GRTgaz?

    Various repair methods are used, from deposition welding to the fitting of a sleeve or the replacement of a portion of the tube.

  • How long does the repair of a pipeline last?

    Adjustments are currently planned over approximately two years: this is to limit unavailability and thus capacity reductions and to ensure that they are compatible with operating constraints.