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    Budapest, Hungary

    Robotechnik

    Renovation of Sewer Pipes in M3 Subway Line

    Address:

    M3 Metro Line, Budapest, Hungary

    Built year:
    1970

     

    Background

    Metro line M3 is the longest subway line in the Budapest Metro system. Also known as the North-South metro line, it began construction in 1970. Today its current traffic length is 16.3 Km, with 20 stations. The maximum station depth is 28.2 m.

    During construction of the stations, a sewer system was built in order to collect the infiltrating groundwater. The channels are made up of steel pipes ranging from DN50-DN250. 

    In December of 2011, the condition of the 30 year old track had become so poor that the maximum speed allowed for the entire line was limited to 60 km/h. The increasing number of track failures was mainly a result of groundwater leaking through the tunnels' deteriorating interior. The harsh groundwater damaged the track plate of the line and corroded rail reinforcements, leading to track defects.

    Since July 2014, efforts have been made to renovate the metro line track. It is expected to take until 2023 until the entirety of the subway line is complete.

    m3 line
    Concrete in Pipes Present a Challenge

    In addition to the track needing renovation, the pipes of the sewer system also needed cleaning and rehabilitation to prevent any future groundwater infiltration. While using a camera during the initial examination of some channels, heavy corrosion and minor limescale formations were discovered. However, the pipes themselves were in good condition.

    Once work began, it was discovered that 75% of the pipes to be renovated contained hard concrete deposits. After examining the hardness and nature of the extracted concrete samples, it was concluded that this concrete entered the sewer during construction.

    Liquid concrete could have entered any fractures or faulty welding seams when flooding rooms and tunnels with concrete. Some parts of the sewer were partially or completely blocked by concrete. As a result, the groundwater drainage system was not functioning to its full potential.

    Other Challenges

    The only access to the work site 20-30 metres below ground was via scaffolding stairs. This meant that all equipment had to be moved up and down by hand.

    Narrow passageways and corridors severely limited the size of equipment which could be used. The size of an inversion drum required for this job would have been to great to pass through many sections of these narrow passages.

    It is forbidden to use any explosive motor device in such enclosed spaces, so anything with a diesel or gasoline powered engine was not an option. In addition to this, a resin that does not emit gases harmful to health needed to be used.

    Concrete in pipe

    When considering high-pressure cleaning as an option, it had to be noted that the renovation also affects the entire fire water network. A high-pressure washer with sufficient water transport could not be used due to the lack of adequate water supply.

    With these challenges faced, the Picote Miller series and Picote Brush Coating™ method offered solutions.

     

    Picote Millers for Cleaning & Concrete Removal

    Prior to renovation of the pipes using the Picote Brush Coating™ method, cleaning and concrete removal was the first step. 

    The unexpected challenge of concrete in the pipes was solved by Picote's most powerful machine, the Maxi Power+ 3-phase miller. With the help of this machine and the right chains and tools, the concrete deposits were removed, and original diameter of the pipes were restored.

    concrete removal
    Picote Brush Coating™ for Renovation

    The Picote Mini Miller and Mini Coating Pump combination was used to apply the coating. Each section was between 7 and 14 meters.

    After cleaning and concrete removal, the conditions of the pipes were generally good. Areas where concrete was removed, but still on the interior surface of the pipe functioned as a corrosion protection layer. 

    Using the Picote Brush Coating™ method, the coating was applied to the interior of the cleaned pipes. This created an effective corrosion protection layer and ensured that the pipes will function properly in the groundwater drainage system. 

    before-after-coating