GEA on the challenges of building an earthquake proof milk plant for Fonterra
The site includes a reverse osmosis (RO) plant, which can process up to 2,000,000 liters a day of ‘cow water’ (water recovered from the milk drying process) and then purifies it for reuse in the factory making it virtually self-sufficient in water.
GEA processing equipment
GEA supplied all the processing equipment including: milk reception, storage, wet processing including standardization and homogenization, evaporation, drying, powder handling, packing and water recovery.
Most of the equipment was built by GEA locally in New Zealand with some specialist items coming from the company’s factories in China and the firm was contracted as a consortium to provide the building work for the project with its partner Ebert Construction.
Gary Reynolds, project manager, GEA, told DairyReporter, the plant was straight-forward in its design except for the base isolation construction, which posed some engineering challenges.
For example, even though the main building is base isolated the ancillary structures are not, which includes every supply line for steam, acid, milk, gas, chemicals or electricity, which has to be able to withstand the building moving by up to 900mm in any plane.
“Our goal was to change the way construction was done in New Zealand. We brought the whole team together in a ‘community’ in which GEA and Fonterra worked side-by-side,” said Reynolds.
“There had to be absolute cooperation between us, the client and the builder. There was some steep learning curves but if we had a problem we talked it through and found a solution together. It was a very refreshing approach. If we had a disagreement we’d get it out in the open and deal with it.”
1934 earthquake with 7.6 magnitude shock
The last time Pahiatua in New Zealand’s North Island was hit by a major earthquake was 1934 when the town was devastated by a 7.6 magnitude shock.
According to Reynolds, to speed the process, and keep costs, down it was agreed not to design a facility that would withstand tremors but to build a copy of Fonterra’s Darfield 1 facility (west of Christchurch) but with base isolation that would allow the building to move in the event of an earthquake.
There are only a handful of other buildings in New Zealand that are protected in this way including the parliament building in Wellington and the country’s national museum.
GEA has many reference sites in New Zealand for this type of plant including Fonterra’s Darfield 2 facility that operates the world's largest milk powder dryer.
The whole plant weighs upwards of 20,000 tons, including its 40-metre-high drying tower, all of which sits on 50 triple friction pendulum bearings that will allow the whole construction to move up to 900mm in any lateral direction allowing the building to withstand a 1/2500 year event without losing its structural integrity.
Each 1.4m square bearing weighs 2.7 tons and has a Teflon center to reduce friction. The bearings were supplied by a seismic bearing specialist company in San Francisco.
Concrete reinforced with 400 tons of steel
Other key elements of the construction include: 3,400m3 of concrete reinforced with 400 tons of steel; the main columns are 17.5 meters long and weigh 16 tons each; and the tower walls are constructed using 517 concrete panels each of 9 tons stitched together using poured concrete.
The corridors between the fixed and base isolated sections have to be able to move too as the building operates under critical hygiene conditions making any breach to ambient air unacceptable.
Although the plant was a copy of Fonterra’s Darfield 1, which meant all the stainless steel components were ready ahead of schedule, designing and building a plant such as this is not without its difficulties.
The building is made from pre-cast concrete panels and columns fabricated in Otaki, on the island’s west coast, and lifted into position. As well as being quick to erect they also provide excellent sound insulation.
However, Reynolds said the 1200mm-square main columns were too big and had to be made off-site and constructed and poured in situ.
The plant started production at 15 tons/hour for Fonterra at the end of August this year. GEA received the order for Pahiatua two years ago in October 2013.