Hydro Scheme Contract Challenges Altex Coatings
For immediate release
July 8, 2004
Hydro Scheme Contract An Environmental Challenge For Industrial Coatings Specialist
Tauranga-based industrial coatings market leader, Altex Coatings Limited, will play a major role in what industry commentators agree must surely rank as one of the trickiest paint jobs ever undertaken in New Zealand.
The assignment is the exterior recoating of the formidable Tuai penstocks at the Genesis Energy Waikaremoana Hydro Scheme in the central North Island. It will entail the external recoating of nearly 4km of steel penstocks over the next three years, starting in January, 2005.
Aside from the complexities of undertaking such a major refurbishment in one of New Zealand's more remote regions, the contractor will need to be mindful of important environmental considerations for the duration of the contract and beyond. Lead in the primer used in the original painting of the penstocks early last century is the big issue; disposing of it is the big challenge.
Graham Matthews, general manager of TBS Farnsworth, the company contracted to Genesis Power to remove the lead-based coatings, says high-pressure water blasting at 36,000psi will be used to remove the coatings.
"No material is allowed to touch the ground, so the entire operation needs to be conducted in a containment system," he says. "Shrouded robotic machinery will be used and backup tarpaulins will collect all waste material."
Matthews says the water and debris collected will have to be sucked or pumped to a water treatment plant which has yet to be built.
"The waste material will require coagulation, so we'll chemically treat it with coagulants and flotulants. The water will be filtered and re-used. Trials have been completed and we await the results of analysis of decanted (clean) water to see whether further treatment is required.
"Solids will be pumped into a filter press. Light floating products will be removed by a sand filter and the remaining material will be disposed of as landfill in Auckland." Matthews says the operation will be unique in that the water needs to be recycled.
"The resource consent allows a five per cent increase in heavy metals in the ambient water flow to go back into the river. As there is no heavy metal in the local water, this effectively means there is zero tolerance of heavy metals dissolved in the water, so recycled water will eventually be disposed on in a certified treatment plant offsite.
Genesis engineering and environmental team leader Richard Bate believes the Tuai penstocks contract will set the parameter for the painting and refurbishment of power station pipes in New Zealand in the future.
"The techniques to be used are cutting edge and were developed in Germany," says Bate. "This is probably a first for New Zealand."
Bate says the reach of the penstocks start at 1.98m and reduce to 1.83m and 1.68m as they run downhill to the power station at gradients up to 23deg. Two constructed in 1929 were riveted and the third, constructed in 1939, was welded.
Altex Coatings' field technical manager, Andrew Webb, says Altex Coatings has a long association with Genesis Energy and the Waikaremoana Hydro Scheme, and with various power schemes throughout the country.
"Major projects we have been involved with include re-lining the Kaitawa Power Station penstocks, repainting the Kaitawa penstock exteriors and scroll-casing lining maintenance to generators at the three power stations situated at Waikaremoana," he says. "And we have specified and provided technical assistance over many years for extensive refurbishment at the Waikaremoana scheme."
Webb says Altex Coatings' experience, in conjunction with its close liaison with local engineers and operators, has allowed for the development of a customised painting process and specification that accommodates environmental concerns during and after a painting project.
"Environmental issues are a vital consideration in the Waikaremoana job. In the event of damage occurring, the specification requires future repairs to be carried out with the absolute minimum environmental impact and with relative ease by non-specialist painting contractors.
"It's not easy balancing environmental considerations with easy application, ease of future maintenance and the demands of a high performance coating system."
The existing coatings on the Tuai penstocks comprise a lead-based primer of 75 microns and a topcoat of 150 microns. Removal of the coatings must be accomplished by ultra-high pressure water-jetting (UHPWJ), a technique Altex Coatings' technical staff are trained and experienced in.
"UHPWJ surface preparation presents a whole new set of challenges requiring a tested and approved epoxy zinc-rich primer suited to, and tolerant of, the varying conditions that will be encountered during the painting process," says Webb.
"Two finish coats of a proprietary vinyl-acrylic coating, Chem-Bar 900, will round off the system providing a durable, low-sheen in the colour specified by Genesis Energy. Chem-Bar 900 has virtually infinite self-recoatability ensuring simple logistics during the painting process and easy ongoing maintenance features."