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Aluminum vs. Stainless Steel Piping for Aquaculture Saltwater Application

2006

Dear Friends,

I would truly appreciate your expertise and advice on the following scenario:
I am currently building a shrimp larvae hatchery in ECUADOR � South America. To produce shrimp larvae we need water temperatures in the range of 30 � 33 °C in the shrimp larvae rearing tanks (L. vannamei, our shrimp species develops much better under these conditions).
Currently the most used method to heat and maintain the water under these temperatures (normal seawater temperature is around 27 °C) is by passing a pipe line with hot freshwater circulating inside, and consequently the "hot pipe line" heats up or maintains the desired water temperature in the rearing tanks. Unfortunately the most common type of pipe used is PVC (probably due to corrosion resistance and low cost) or common steel pipe coated with epoxy painting. However, both alternatives have great disadvantages:
- The PVC pipe is highly inefficient for heat transfer
- The epoxy coated steel pipe usually lasts very short time and becomes corroded very quickly, plus it needs constant maintenance, not many coatings are available for aquaculture use due to toxicity issues with the shrimp larvae.
The diameter of the pipe is � inch, the velocity of the water going inside the pipe is approximately 1.5 m/s and the temperature is approx. 70 °C, the water of the rearing tank (outside contact of the pipe) is in constant movement due to aeration requirements.
After searching and searching I have found three possible local alternatives (in � inch piping):
- Stainless steel grade 304 pipe with a cost of U.S. $2.9/meter (schedule 10).
- Stainless steel grade 316 pipe with a cost of U.S. $7.6/meter (schedule 10).
- Aluminum pipe (I am not aware of the specs.) with a cost of U.S. $2.5/meter (slightly thicker than schedule 10).

Please help me out to make the best decision.

I need approximately 500 meters of piping. Seawater to be heated is 33 ppt salinity.

Thanks a lot for your time and help!

Luis Arturo Granda
Excellaqua - Machala, ECUADOR

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2006

Hi there,
Essentially, an epoxy coated steel tube should have done the job for a long period of time. The problem might be not the epoxy coating by itself. Correctly formulated epoxy coatings are approved for this type of use such as treatment plants like Aquamar, and Empagram have already done.
Have you checked if the epoxy coating is solvent free, 100% solid contents?

Guillermo Loayza
- Quito