T500 Depth Rating

[gcelec (Geoff Cook - SeaView Systems)]

The T500 thrusters are rated at 300m but the T200’s don’t have a depth rating.
What is the factor that limits the T500?
Is there a depth rating for the T200?

[etienne (Etienne Demers)]

Hello guys,

for the T500, the depth rating is said to be 300m. Any chance it can work in 500m? Isn’t it the same potted design as the T200?

Cheers,
E.

[EliotBR (Eliot)]

Hi @etienne,

@etienne

for the T500, the depth rating is said to be 300m. Any chance it can work in 500m? Isn’t it the same potted design as the T200?

I’m not certain what the reasoning was here, so I’ve asked about it and will get back to you

[EliotBR (Eliot)]

@EliotBR

I’m not certain what the reasoning was here, so I’ve asked about it and will get back to you

Following up, initial validation samples had some issues with delamination around the cable at large depths. We’re working on a process to mitigate that, but that hasn’t yet been fully validated, or implemented on the manufacturing line.

We wouldn’t recommend using T500s that have been produced with the existing process beyond 300m depth without using a water-blocked connector (to ensure no water ingress to the enclosure via the cable), and testing prior to deployment.

[etienne (Etienne Demers)]

Hi Eliot,

I do a bracket that houses the ESC which is oil filled. One side is a cobalt connector the other is wetlink going to the thruster. In this condition the Thruster cable is balanced. As long as the Potting on the thruster coil and contacts are good. Shouldn’t be an issue.
What do you think?

Cheers,
E.

[EliotBR (Eliot)]

To me that at least seems reasonable in theory. That said, I don’t have experience with oil-filled enclosures, so don’t know how resistant oil is to allowing in bubbles of water in a rigid enclosure, and whether that’s dependent on the temperature, pressure, and type of oil involved.

[etienne (Etienne Demers)]

I see the ESC’s have Electrolytic capacitors. Are these essential?

[EliotBR (Eliot)]

The Basic ESC 500s use COTS (commercial off-the-shelf) PCBs, so we can’t really say, because we don’t have the detailed reasoning behind the design that would enable us to suggest whether a non-hollow capacitor alternative could be suitable.

UPDATE:

@rbanerjee

The caps are for input capacitance - they are necessary.
You can replace with any appropriate value of solid state capacitor.
It may be worth adding a conformal coat with epoxy or RTV before oil exposure. Pretty standard in motor drive world.

[EliotBR (Eliot)]

Hi @gcelec,

@gcelec

What is the factor that limits the T500?

I’ve moved some older comments here from the original T500 launch thread, since they’re relevant to this discussion.

I don’t believe there have been any updates to the production process since that initial discussion.

@gcelec

Is there a depth rating for the T200?

Short answer (from the Technical Reference), they’ve been tested to work to at least 500 msw.

Slightly longer answer (from the T200 product page):

@T200 Thruster: FAQs - What is the depth rating of the T200 thruster?

We do not have an official depth rating for our thrusters, as we haven’t found a limit yet. Due to the unique fully flooded design where water freely moves throughout the thruster internals, pressure isn’t much of a concern. There are no air cavities to compress, or seals of any kind. Our thrusters will function well to at least 500m or so.

[XYZEng]

Hi Eliot,

We have an ROV system made of Bluerobotics components.
The T500s are the components with the lowest depth rating.

@EliotBR

We wouldn’t recommend using T500s that have been produced with the existing process beyond 300m depth without using a water-blocked connector (to ensure no water ingress to the enclosure via the cable)

We have cobalt connectors and I’m trying to understand if they’re considered water-blocked connectors. But either way we also don’t want to get water inside the cables.

I understand you have a depth rating for a reason, and we understand that it’s our risk to bear. But I’d like to understand the risk of operating at 350m depth.

Can you share any info on the depths the delamination around the cable began to occur?

FYI our T500s are new, so if there’s an updated model that mitigates this risk it would be great to know if there’s a new model number or month of manufacture where these issues are no longer a problem.

Regards,
Kieron

[David105 (stuard)]

Any update on this topic? does someone knows if using connectors for example, from https://www.bluetrailengineering.com will increase the depth rating?

thanks in advance

[Jacobrov (Jacobo)]

Hi, just saw on What is a Thruster? - Blue Robotics that outland technology has a 600 meters depth rating rov that uses T500, the rov in question is the ROV-3000.

this might imply that the T500 thruster should be capable of reaching 600m without problems.

Fascinating stuff.

[odedezra]

Hi Eliot,

It would be great to know if there are any news or conclusions on how to improve the T500’s depth rating. Planning to take it to 700m+. Thanks!

[EliotBR (Eliot)]

A minor update here - our T500 production process did undergo a cable quality upgrade near the end of 2023, which should reduce the cable delamination issues I mentioned previously, but there’s still some testing we need to do before we can update our guidance for depth capacity.

We are also working on some more significant design changes to our thrusters that should allow us to provide a more robust and consistent rating for them in future, but I don’t have a timeline on when those changes will be validated or implemented in production.