equipment

Dome port repairs

I had a bit of a shock as I stripped my housing down after my previous dive, when the “dome” of my dome port fell off! I discovered that my vacuum leak detection system had been all that stopped my housing filling with water in a catastrophic way. Looking up the replacement cost of the dome gave me a great encouragement to make a DIY repair…

The dome, which is a Sea&Sea mini dome, is constructed from an aluminium base, with an acrylic dome held in place by a bead of sealant. I have been using this dome since 2004 and has done hundreds of dives. I was able to gently pull the whole bead of sealant off, which left not a trace on the acrylic but some residue on the aluminium base. I carefully removed the latter using a flat plastic blade I made by applying a scalpel to a “bic” pen lid. I then carefully cleaned both parts with alcohol.

I did notice that I’d managed to make a hairline scratch on the *inside* of the dome (presumably through careless cleaning or handling), so I took the opportunity to polish the inside using my kit… Whilst I had easy access to the inside surface.

A question on the BSoUP Facebook page directed me to a product called TSE399 from a company called Techsil. Whilst some have used standard bathroom sealant to make a similar repair, this seems to have mostly been “in the field”. The difference between the Techsil product and standard bathroom sealant is that the former flows and the latter does not, as well as being quicker setting.

The acrylic has a groove around the edge, whilst the aluminium has a rebate, into which the dome sits. It seems that this is what provides the seal, as well a large creating a bead to hold the dome in place. The TSE399 is said to have excellent adhesion to both plastic and metal; I hope so, as it’s all that’s holding the dome in place!

To fit the dome, I decided to run a thin bead of sealant into the rebate on the port base. I let this cure for a few minutes, with the idea of creating a bed for the dome to sit on. This didn’t work as well as I hoped, as it did not set enough, so when I placed the dome in place, it sank into the sealant and a small amount overflowed. The final step was then to run a thin bead into the groove in the acrylic. It’s important to keep the dome flat until the sealant has solidified, as it will flow, which creates a smoother finish than I think I could have achieved with something similar to bathroom sealant.

Having left the dome alone for 36 hours for the sealant to cure, the final step before pressure testing was to give the exterior of the dome a quick polish to remove the one or two scratches it had picked up in the last couple of years; I’m sure these did t show in the images; tiny scratches fill with water and disappear from view underwater, but I wanted everything to be as shiny as possible before returning to use.

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