Save our seals, salmon and safety

An Australian designer has played a key role in producing a world first in aquaculture – a salmon protection pen that not only protects the fish, but also safeguards the seals that want to eat them and the staff who might be caught in the middle.

John Rafferty of Elemental Manufacturing designed and manufactured essential components and injection moulding tools for the environmentally harmonious pen for Australian salmon farming business Huon Aquaculture.

Huon describes the pens as “revolutionising the salmon industry worldwide,” and praises 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 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 tasty fish inside. It also allows easier and wider egress for the disappointed seals.

Because the double net design is 40 per cent wider than conventional designs, a challenge for Elemental was to produce a triple collar stanchion (below) that was strong enough to cope with the flexing and stresses imparted by the wider design.

“Many suggest that this revolutionary pen design should be adopted as a new global standard,” says 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 John designed for Huon was the triple collar stanchion (top picture), 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 (picture below).

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.

John 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 short-term loads,” says John, who ultimately engineered a design that was not only ideal for the purpose, but which also offered considerable savings of money.

Some of the benefits of replacing the existing metal stanchions with an engineering polymer include:

• A reduction in price of more than 50 per cent compared to the current metal fabricated units.
• A significant weight saving, from 160kg down to 55kg, which allows for larger pens and therefore increased and more efficient production. This weight reduction decreases the energy needed to move the pens, both during assembly and in operation on the water.
• Service life – the metal units can corrode over time, while the polymer units are designed to last at least 10 years, with an expectation of a serviceable life of 20 years or more.
• The polymer stanchions have a significant amount of controlled flexibility, compared to the metal units. Under heavy loads, this allows many of the forces to be diffused throughout the assembly compared to the metal stanchions, which are unforgivingly rigid. Diffusion of forces results in less damage to the pen‘s components during storms and rough conditions.

“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,” says John.

“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, John 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, John’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”.

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