Repair Filter Outlet Assemblies at a WTP

The Repair of Filter Outlet Assemblies at a Water Treatment Plant

Overview of Project:

The filter outlet pipework assembly and isolation valve spindles (12 in total) at a water treatment plant required refurbishment or replacement.  The pipework and valves have varying levels of corrosion and some surfaces are not coated to prevent corrosion.


As a member of the client’s water maintenance and minor works  maintenance has been undertaking maintenance work on water sites for the past 3 years.  This has enabled Metal Maintenance to gain a bank of knowledge with regard to the requirements of working on water treatment and waste water treatment plants.  We are very aware of the need to ensure that plant availability is of high importance to the client.  On award of the tender Metal Maintenance will meet with the Superintendent’s Representative to ensure all works to be undertaken do not interfere with client’s operations or risk the integrity of water supply.

Scope of Works:

Repair Filter Outlet Assemblies, which includes:

  • Remove rotork actuators, pipework and valves (x 12)
  • Fabricate new 375NB pipe spools, rotork actuators stands and drive shafts, sandblast, powdercoat and ceramic coat. (x12).
  • Supply new seals (gibaults and uniflanges) (x12)
  • Supply stainless steel universal joint (x12)
  • Needle gun and prepare remaining pipework, colour match paint (x12)
  • Reinstall and commission new pipework and valves (x12)
  • Clean Spa Baths (x12)

Construction Activities:

Work Methodology included:

  • Preparation of SWMS, JSEA and Hazard Assessment prior to commencing work,
  • Only two filters can be off-line at any given time so work will be carried out in 6 groups of 2 each,
  • To achieve the required Date for Practical Completion Metal Maintenance proposes the following:
    • When on site removing the first 2 of the 3-way spools we will take measurements for all 12 spools

  • The first 2 spools will take the estimated 3 weeks turnaround time
    • Fabrication, sandblasting and painting of all 12 spools will be undertaken in advance
    • Turnaround time for the remaining 10 spools will therefore be substantially reduced to 1 ½ weeks.
  • Adjacent “spa baths” will be covered to prevent contamination of water.
  • Barricading will be used to restrict access to “spa baths” as they are taken offline
  • The filter pipe outlet assembly will be removed using a compliant prefabricated crane supplied by the client and already on site
  • New blinds will be supplied and installed to allow the backwash to be refilled to meet the client’s operational requirements
  • Existing pipework that cannot be removed will be prepared using needle gun and sanded up to concrete wall and painted to colour match
  • Ceramic coating will be applied inside the pipe to accessible areas only


The project was completed on time and on budget.  The client was happy with the works completed.

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