[PSUBS-MAILIST] K-250 side viewport and dome hatch.

[Sean T. Stevenson via Personal_Submersibles]

In fact, there's nothing inherently wrong with rectangular cross section seals, provided they are implemented in the same manner as O-ring seals with a captive groove, managed extrusion gap, designed gap fill and designed maximum squeeze of the seal. Absent those controls, a simple flat gasket presents not only a severe risk of extrusion, but can be subject to damage and consequent failure if maximum squeeze is not constrained. When properly designed, however, rectangular cross section seals can perform essentially as an O-ring seal with integral backup rings in terms of extrusion resistance.

Standard O-ring seals have the advantage of having a massive body of performance data available, and a freely available comprehensive design resource in the Parker O-ring Guide (ORD5700). Seals with custom geometries will generally require independent design verification in the form of FE models and destructive testing.

Sean

-------- Original Message --------
On Sep. 27, 2020, 18:10, hank pronk via Personal_Submersibles < personal_submersibles at psubs.org> wrote:
Hi Philipe,
You have to machine the dome seat flat anyways, so adding an o-ring groove is a small extra step.
Hank

On Sunday, September 27, 2020, 4:36:22 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi Philipe,
I don't know of any submersibles that don't use o-rings as the hatch sealing method.
I believe there is a danger of a flat rubber seal extruding inward under pressure.
Alan

On 28/09/2020, at 10:32 AM, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Follow the plans. The sections you reference are all related to the pressure hull and should not be modified.

Jon

On Sunday, September 27, 2020, 04:47:54 PM EDT, Philippe Robert via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi all,

I currently make the conning tower. I see on the internet some k-250 with front and side viewport in addition of the acrylics dome. Some of the viewport is close to the gusset and I assume that is not possible to do a 100% weld. Is it acceptable ? Is it ok to drill hole in the viewport to put retaining bolts ? Second question, on the blueprint, the sealing option for the hatch on the conning tower is o'ring groove. Is it possible to make better sealing like flat rubber strip or something like that ?

Best regards,

Philippe
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