- Waterco designed hyperbaric chamber a world first
- Replicates deep ocean conditions for accurate fisheries testing
- 8-bar (800pa) filter waterco’s highest pressure rating
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A specially designed hyperbaric sand filter chamber which replicates deep sea conditions up to almost 70 metres is key to a vital Australian project into the affects of barotrauma on fish which are rapidly brought to the surface and then released. The chamber was designed and created by Waterco Ltd in conjunction with aquaculture specialist Aquasonic.
The Wild Fisheries Program, a division within the NSW Department of Industry & Investment which undertakes scientific research into the sustainability of fish stocks in NSW, has received funding from the NSW Saltwater Recreational Fishing Trust to conduct a series of tests into fish barotrauma. Barotrauma is the physical damage caused by a change in pressure and is particularly dangerous for fish when they are brought to the surface from great ocean depths. The gases trapped in the fish’s blood, tissues and swim bladder expand faster than they can be expelled and can cause injury or death.
 The key challenge for the research team was that they needed a high pressure chamber that would replicate the exact pressure conditions of the deep ocean.
“Previously, no experimental fish hyperbaric chambers have ever been built that could withstand more than four atmospheres of pressure,” explains Dr John Stewart, senior research scientist, Wild Fisheries Program. “As most of our offshore fish are captured from depths much greater than 30m, we needed a chamber that could withstand greater water pressures.” “Not only that, we needed a chamber that was large enough to keep big fish (up to 7kg snapper), it also had to have flow-through salt water, be able to handle internal pressures of more than seven atmospheres – and we had to be able to see the fish inside.”
Setting benchmarks
Waterco is one of only a few companies worldwide which manufacture large high pressure rated filters, using the latest in fibreglass winding technology. This ensures superior mechanical and chemical resistance and tanks which weigh just one third that of steel and are non-rusting and non-corroding.
When the Wild Fisheries Program approached Waterco’s distributor Aquasonic they knew they had come to the right place.
“Wild Fisheries needed a high pressure-rated filter and we knew we had just the right solution,” says Bryan Goh, group marketing director, Waterco. “Using our 8-bar filter, the Wild Fisheries Program can now carry out tests to more than seven atmospheres - at least 60 metres - which they haven’t been able to do in the past.”
The growing desalination industry, in particular, uses such filters (6-8-bar). Waterco uses the latest in fibreglass winding technology, ensuring vastly superior structural strength, mechanical and chemical resistance, and tanks which weigh just one third that of steel and are non-rusting/corroding. Its 8-bar filters have also been used for water treatment applications such as pre-filtration for reverse osmosis / membrane systems.
The 8-bar (800kPa) pressure rating is the highest that Waterco can currently achieve. “Its construction and multiple layers of continuous fibreglass enable the filter to withstand a high internal pressure,” explains Bryan. “A project such as this really demonstrates the strength of our commercial filters.”
And after significant research and development, Waterco’s proprietary technology and advanced manufacturing capabilities enabled it to incorporate sight glasses and large manholes into the high pressure filter.
“For two years, we tested various methods of installing large manholes and sight glasses,” says Bryan. “Generally, large manholes and sight glasses are harder to incorporate in high pressure filters, because any opening in a filter vessel creates a potential weak point or complicates the manufacturing process. The 80mm sight glasses Waterco has installed for this project were specially designed and developed by our fibreglass engineers. Such filters are also suited for desalination plants as pre-filters, prior to the membrane filters.”
Vital survival tests
“One aspect of this research is into the survival of fish following being captured and then released,” says Dr Stewart. “Catch and release fishing by recreational fishers is a practice designed to enhance the sustainability of fish stocks, but fish that are captured from even quite shallow waters can suffer from barotrauma injuries.
“Thanks to our new chamber, we’re conducting a series of experiments on these species to examine their behaviour and survival following simulated pressure changes from different depths. We will investigate ways of improving the fish’s health and survival rates.
“The chamber is working very well and maintains constant pressures of up to eight atmospheres indefinitely. We are using a submersible well pump to pump the seawater into the chamber under pressure and we are able to clearly observe the fish within the tank through the sight glasses.”
Most advanced program of its kind
Whilst there has been some research into fish barotrauma around the world, the Waterco-designed hyperbaric chamber makes the Wild Fisheries Program the most advanced of its kind.
 “Previous field-based research into the effects of barotrauma has been hampered by factors such as damage from being hooked, and stress during the fight,” explains Dr Stewart. “Many people have used tagging studies, however it has proven difficult to recapture enough fish to achieve statistically significant results. Other studies have maintained fish in cages - which can be difficult due to changing weather and sea conditions.
“Until now, no experimental fish hyperbaric chambers have been built that could withstand more than four atmospheres of pressure. As most of our offshore fish are captured from depths much greater than 30m, we needed a chamber that could withstand greater water pressures.”
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