Depth rating over time of acrylic enclosures

Hi! We’re making a prototype of an ROV of sorts, which will be deployed up to a few months (less than 100m) and go to the surface several times daily. We’ve been wanting to use acrylic enclosures (4") for visual purposes, but recently noticed a recommendation on the watertight enclosure page stating that “the depth ratings for cast acrylic components are applicable only for short-term submersions lasting less than two weeks. For longer submersion, we suggest using aluminum components only.”

This raises the question if this is simply a very precautionary note, or something that we should be significantly concerned about? I would have thought that acrylic should be OK for us practically speaking, but of course aluminum would still be the more reliable/durable choice long-term.

Any experiences, negative and positive would be helpful. Thanks!

We’ve got a similar question about long term deployment and I figured I’d give your thread a quick bump. We want to use a housing for long term video surveys so we require at least the end caps to be acrylic. Were you able to conduct any testing?

Hi @UltraFred and @FLUGATRON -
The note on the product page about Acrylic is the result of feedback from some customers at Woods Hole Marine Lab - if acrylic enclosures are used at depths greater than 25-30m for more than 2-4 weeks continuously, the acrylic will “creep”, resulting in failure of the enclosure! This is because acrylic is somewhat like glass, and flows very slowly when under high pressure.
For applications where the pressure is reduced, this should be less of an issue? Generally acrylic is more vulnerable to shock-impacts causing failure…


We have seen a lot of ‘crazing’ in the acrylic tubes, especially in the areas where any pressure is applied.

In some of our data buoys we use the 3" locking version, and with the constant thermal changes and only one end being in the water we see quite a bit of thermal shock evidence.

We also have some buoys on taut tether, and in high seas they go through wave period cycles of surface to 3m deep for 1000s of iterations.

We haven’t had one fail, but we are certainly keeping a few in the field to see when it happens. Thank goodness for leak detection!



@tony-white and @FieldWerx -

Thank you for the input! Sounds like either the acrylic or aluminum housing will work for our application then. Appreciate it!

Appreciate the replies! Sounds like acrylic must be properly time-tested under relevant conditions to be considered safe. Great to hear that they have worked for you @FieldWerx, I would be interested to see if one does fail.