Braithwaite Tanks Case Study 332

Severe corrosion had caused substantial holes to develop on the Braithwaite Water Tanks. The roof was repaired utilising steel plates. The smaller holes were repaired using a combination of metal filler and GRP bandaging in conjunction with Acothane DW.

A London hospital recently had a problem with two Braithwaite water tanks. Both tanks are located in a roof top plant room and had previously been internally lined with a butyl rubber liner.

Braithwaite water tank Issues with the Braithwaite Water Tank

The right photograph show one of the tanks fitted with the butyl rubber liner which poses a number of issues as listed below:-

  • The steel tank continues to sweat & corrode underneath the liner.
  • The underside of the tank roof remains untreated.
  • Tank struts are often removed.
  • Chlorine attacks the rubber making it brittle, causing it to crack.
  • Sediment becomes trapped in the folds & creases of the liner making subsequent cleaning very difficult.
  • Personnel entering the tank can easily puncture the liner.

Bitumastic coating applied to the underside of the tank roof no longer carries WRAS approval.

The client needed the tank to be relined in accordance with the latest water regulations and operational as quickly as possible. After looking at several options, Acothane DW was specified for the following reasons:-

  • Approved for use in Public Water Supplies – Regulation 31(4)(a)
  • Fast curing time so the Braithwaite tank could be operational as soon as possible
  • Proven life expectancy of over 10 years
  • Flexible with excellent elongation properties
  • Tough – high impact and abrasion resistance
  • Solvent Free Polyurethane
  • Easy to clean making future maintenance simple
  • Exceptional track record

How we restored the Braithwaite Tank

Inside a braithwaite tankA suitable sub-contractor was chosen to prepare the Braithwaite Water Tank and apply the Acothane DW coating. The failed butyl liner was first removed and the sectional steel tank was then manually prepared to provide a surface profile to promote optimum adhesion of Acothane DW. After preparation, all dust, residues and debris left on the surfaces was completely removed.

All exposed & protruding rubber jointing strip was cut back until flush with the steel substrate. All joints were then filled with Acothane Mastic Grade that is specifically designed for application by trowel, stiff brush or spatula and is completely compatible with Acothane DW.

Two coats of Acothane DW (Cream followed by Blue) was then manually applied by brush and roller to provide a tough, flexible, ceramic-tile like finish. During application the operatives carried out regular checks of wet thickness with a wet film thickness gauge to ensure the specified thickness was applied.

To comply with DWI regulations the Acothane DW coating was left to cure for 7 days before re-commissioning.