Flange design

[JourneymanEng]

Fellow engineers - I have a problem.

Outline: Flange design theory and RsOT. Where can i aquire a design resource that covers the basic rules on designing an adequate flange?

Details: A gas turbine requires a seal at the combustor outlet. Our engine casing design prevents flange access over a 90deg section of the flange. Algor shows a 10 fold increase in deflection under load.

I need to know a better way to seal given the constraints:
- No access to one side of the flange over that 90degs.
- limited access to the opposite side - Manual assembly difficult due to recup duct. I could alter but improvement would be neg.

This problem is compounded by my failed efforts to find a good resource for flange design. At the very least can anyone recomend one?

Most greatful

Journeyman

 

[JohnBreen]

Hello Mr. Engineer,

Have you seen this thread:

thread292-16934

You may find some insight there.

Regards, John.

 

[StressGuy]

Assuming we're talking about a flange of some decent size (i.e. large enough to be more than a 4 bolt connection), I would think you are going to have an extremely difficult time getting a good seal if you can't access a 90° arc of the flange. Edward L. Klein
Pipe Stress Engineer
Houston, Texas

All opinions expressed here are my own and not my company's.

 

[mgp]

Would it be an option to replace the flange with a Grayloc type clamp connection?

With this you would have only two points (0 and 180 degrees) for access, although you have to get the clamp around first.

It may even be possible to get one with bolts only at one side. Whether that exist for high pressure applications I don't know, but it does for low pressure.

regards
Mogens

 

[JohnBreen]

Hello again,

Good thought Mogens!

Maybe a Reflange G-con would suit the application. We use these a lot in high temperature piping (they make them in exotic materials if needed)where we can't get at the bolts to tighten them (Nuclear waste encapsulation in foam glass). Just a thought.

Look here:

http://www.reflange.com/

Regards, John.

 

[Mechy]

Have you tried the "victaulic clamp" option. There may be a temperature/ pressure limitation.

 

[abeltio]

Journeymaneng,
From the description of your problem seems like the flange design is the least of your troubles... the combustor outlet (if we are talking about the same thing) is about the hottest part in the whole unit.
I do not know what make/model of GT you have... I 've been dealing with GT's for quite some time now and sealing the combustion zone is extremely difficult (high press/temp). Depending on the location of the joint in the unit you may use a C-seal, graphite filled spiral-wound gaskets or metal-to-metal contact.
As you cannot pressure test a gas turbine, any mod is intrinsically a gamble. E.g. the gaskets I have seen are nothing like any standard gasket for piping (width is way much smaller)
Also consider that you may have to modify a flange in a casting (if it is on the casing) and the flange materials themselves will not be good ol'carbon steel.
All this said... the OEM should be contacted and made aware of the situation, they may have already a mod developed that will save you $$$ and a lot of headache.
HTH
Saludos.
a.

 

[JourneymanEng]

Engineers all,

Thank you for your advice, I thought it best to give some sort of update to the problem. Around the time of posting this question I conducted some rudimentary checks on the proposed system using Algor. It seems that for 15mm thick flange of circa 300mm diameter, the loss of one out of eigth equispaced fasteners results in a displacement increase of 10 times the original (in simulation).

Your advice reinforces the idea that there are limited cost effective solutions to this problem. Of importance is that this design must be a low cost GT and as such expensive materials and 'experiment heavy' processes are outside my scope (though quite reluctantly).

Of note is that the standard flange solutions such as the G-Con and those in the Taylor Forge ref were difficult to apply here due to parts of the GT getting in the way.

My solution: I have extended the length of the design and have created two separate flanges. Not the most Triz of solutions but one that will most likely work and importantly allow me the scope to add more fasteners (or just torque the bst'd up) should the design prove inadequate.

Testing in another few months. Will add a note for the benefit of those interested.

Again many thanks,

Journeyman

 

[arto]

How about SAE 4-bolt flanges? see

http://www.anchorflange.com/

they make split ones too