Archco-Rigidon lining cures rotten egg gas problem

Citation

(1998), "Archco-Rigidon lining cures rotten egg gas problem", Anti-Corrosion Methods and Materials, Vol. 45 No. 4. https://doi.org/10.1108/acmm.1998.12845dab.006

Archco-Rigidon lining cures rotten egg gas problem

Methods

Archco-Rigidon lining cures rotten egg gas problem

Keywords Coatings, Denso, Pipes, Sewage

When Blackburn Borough Council, UK received a number of complaints about a rotten egg smell emanating from one of the sewers they look after for North West Water they were at first mystified as to the cause. The effluent itself was relatively innocuous and did not have a strong nose. However, it was very strong around the cast iron pipe bridge that carries the effluent over the Davy Field Brook on its way to the treatment plant.

After some investigating the smell was identified as hydrogen sulphide (H₂S), known to the layman as rotten egg gas. Although smelling strongly the amount of H₂S was comparatively small and was produced by slight traces of sulphuric acid in the effluent reacting with the cast iron pipe. The condition of the metal manhole covers and frames, which were corroded, appeared to support this theory.

It was decided that coating the interior of the cast iron pipe would protect it from further acid attack and the production of hydrogen sulphide, and thus eliminate the smell. To assist in this project Blackburn Borough Council called in Repair Protection and Maintenance Ltd, corrosion engineering and specialist coating contractors from Pontefract, West Yorkshire, UK. After inspecting the site and carefully assessing the chemical environment and application problems, RPM selected Winn & Coales' Archco-Rigidon 403D, a flake glass filled vinyl ester, as the most suitable coating for this particular problem (Plate 3).

Plate 3 The Archco-Rigidon 403D lining applied to the interior of the cast iron pipe by RPM

Surface preparation and coating of the pipe had to be carried out without disrupting the effluent treatment process at the nearby paper mill which discharged into the sewer. To achieve this the work was carried out during the Christmas break, when the effluent flow was at its lowest. The first phase of the job was to install an over pumping system, complete with standby pump, running parallel with the cast iron pipe and then rejoining it via a manhole, so as to divert the flow while the internal coating work was carried out.

The pipe was given an initial clean by Blackburn Council's operations department using one of their jetting tankers after which the pipe internals were grit blasted by RPM to Swedish Standard SA 21Ž2 using specialist down pipe grit blasting equipment which was pulled through the 13.5in. diameter pipe.

An air-driven pipe coating machine was then deployed to apply the Archco-Rigidon lining. This machine is fitted with an air driven spinning head and expanding legs which self centre the wheeled carriage. Three passes were required to give the desired overall coating thickness of 1.5mm.

Despite the adverse weather conditions the surface preparation and coating work was completed within the agreed time frame with no interruption to the effluent flow, nor spillage of effluent into the stream.

Details are available from Winn & Coales (Denso) Ltd. Tel: + 44(0) 181 670 7511; Fax: + 44 (0) 181 761 2456.