Protecting salmon and seal

IN SOME countries, seals are eliminated when they try to get into pens where salmon are bred. Whilst only natural for seals to do so for survival, they get hurt trying to enter these pens. To protect both the fish and the seals, John Rafferty of Elemental Manufacturing Pty Ltd designed and manufactured essential components and injection moulding tools for an environmentally harmonious pen for Huon Aquaculture, an Australian salmon farming business. This protection pen is a world first in aquaculture.

Huon refers to it as “revolutionising the salmon industry worldwide,” and considers John’s involvement as instrumental in realising the design and producing parts for half the cost of metal fabricated designs yet which last longer.

“In most countries outside of Australia and New Zealand seals are destroyed by farmers as a pest,” says Mr Rafferty. “These seal-proof pens are designed to protect seals and prevent them from being destroyed as a result of them continually attacking the pens to get at the fish.

The new pens employ a double-net system to protect the salmon and prevent seals from ramming themselves against the inner netting to get at the fish inside.It also allows easier and wider egress for the disappointed seals. Because the double net design is 50% wider and more stable than conventional designs, a challenge for Elemental Manufacturing was to produce a triple collar stanchion that was strong enough to cope with the flexing and stresses imparted by the wider design.

“The new pens also create a safer working environment for staff with a new flat walkway that also helps keep aggressive seals away from workers. Many suggest that this revolutionary pen design should be adopted as a new global standard,” says Mr Rafferty, whose background was in toolmaking before he started his business, Elemental Manufacturing, at Wangi Wangi in NSW. The business provides clients with industrial design of injection moulded parts and injection moulding tool design, which includes supply and tool commissioning.

One of the important parts of the design for Huon was the triple collar stanchion, which he says is the first and only 450mm plastic injection moulded triple collar stanchion for aquaculture. At 2.5 metres in length and weighing over 50kg, this part is used to support the entire pen and houses the three flotation collars (pipes) that keep the pen afloat.

The design also includes a fully enclosed walkway and handrail for workers to be able to move safely around the entire circumference of the pen.

As well as the challenges of designing a part that will perform in the conditions and meet all the safety requirements, it was of paramount importance to create a shape that can physically be moulded. Mr Rafferty faced the hurdle of designing a tool that would not only allow the part to be moulded, but to ensure that any weld lines generated during the moulding process were in the lowest stressed regions of the stanchion.

“This was no easy feat, as this part is the backbone of the salmon protection pen, and is subject to a myriad of both long and shortterm loads,” says Mr Rafferty, who ultimately engineered a design that was not only ideal for the purpose, but which also offered considerable savings of money.

“As far as injection moulding is concerned, this +50kg, 2.5m long part is considered extremely large; this together with the 25mm wall thicknesses meant moulding the part would be demanding for both man and machine,” he explained.

“Our success in designing and moulding these extremely large volume parts allows for a rethink on the existing boundaries of what can and cannot be achieved within this industry.”

A champion of Australian design and manufacturing, Mr Rafferty says the success of this project paves the way for many new products that were previously considered “not possible” to be looked at in a different light as we continue to push the existing boundaries to suit our ever changing needs.

Following the first success, Huon Aquaculture has again engaged John’s services to commission a larger, heavier version of the product for their continuing expansion. The next size, still in tooling production, will weigh more than 65kg.

To support the Australian polymer industry, Mr Rafferty’s company worked with a local Australian injection moulder, Wasson Engineering Plastics, who have proven to be very competitive compared to overseas moulders. Wasson assists Elemental Manufacturing with commissioning and running of the moulding tool “and ensuring that our local industry not only survives, but grows and is sustainable.”