Metal to Metal Sealing

Laser welding might work.

Yes and no. At the lazy B ranch (Boeing) we tried all and the best results , for our configuration, was EB. However the application cost many $ and is very difficult to perform NDT.

Ron

you are'nt giving enough info to give you a good answer. what'the reason for the flange? why not just weld the joint>

Can your design allow for a metallic gasket (corrugated, soft, or otherwise deformable), or must it be flange-to-flange?

Or can you use a "Van Stone" type of flange, where the pipe or tube ends are flared 90° and compressed between back-up rings?

You can have a look on DG fuel injection pipe joint.

1) First there are at least two channels and may be necessary disassembly the body so is not possible use weldings or highly inconvenient;2) The pieces are small, and so the mounts of fluid in the circuit.Is not an hydraulic circuit for a crane so not fittings like JIC37,5;or 60 against ball nose or 75 degrees,90 is a new one for me but anyway..Must be flange to flange.I saw this in fuel injectors Assemblies and i am trying remember if any injector have not.You can get any info when work is thru cutting tools but some kind of obscurantism appears as a hidden science when you talk about surface finishing utilities.Why's that?

Any why can't you use an O-ring?

I am using an hydraulic circuit to control small amounts of fluid in other h.circuit.Perhaps the compressibility of fluid at that pressure introduces a .5% volumen displ. even when rubber is almost not compressible it could need some adjusting into its hub even in a submersed assembling perhaps adding bubbles,what about timelife: in such case i should use a washer,copper or aluminum,(by the way i couldn't get the proper depth of its hub like any rubber o'rings manufacturer provides), isn't it much better? is neither a big deal send to make instead, plastic dishes like poliurethane or even ptfe but is not easier or more prolix design just a metal to metal join? (no!i don't want neither a whole metal gasket covering the flange!) why not and how to, are my questions here.-

I work in Industrial Hydraulics, and use O-ring flanged connections daily with no issues, and they are readily available from the manufacturer.

Are your pressures above 10,000PSI?

The amount of compressibility in hydraulic oil is negligible for all practical applications.

From the information provided (and understanding you want some secrecy as to your reasons) I'll provide a suggestion that might be of benefit.

I would separate the two parameters that you are trying to achieve ("Mechanical attachment" and "high pressure seal") from each other in the joint design.

Having your flanges to provide the mechanical attactment of the pipe sections will stop relative movement, but sealing at the same time would be difficult.

Suggest that your pipe ends be matched tapers (maybe with .005 degree difference in angle) and have the pipes be a sleeve fit OD inside ID of next section. (Maybe using thermal expansion of female pipe to assist fitting and dismantling) This achieves the seal.

(Your nominated materials might preclude the sleeve fit concept due to potential galling, but just dropping this on the table for your consideration.)

I know you don't want an o-ring, but there are o-rings and there are o-rings. Metal o-rings can be internally pressurized during manufacture, or can be slotted on the high pressure side to be self-energized. They are commonly used on nuclear systems, submarines and other locations where you could not consider an elastomer.

Here's one popular range of them:

http://www.globalspec.com/FeaturedProducts/Detail/TrelleborgSealingSolutions/Wills_Rings_Metal_Seals/47183/0

I love the way they manufacture the pressurized ones: trap a size-calibrated pellet of sodium azide inside the hollow ring, heat the pellet so it explodes and (mostly) nitrogen pressurizes the ring.

Mark Bingham
Relativity PL

Hi,

May be you can consider "Labyrinth" type of joint.

By the description this looks like packing cups of reciprocating compressor piston rod packing. These cups are lapped and connected and two channals passing through these cups are cooling water and lubricating oil. The assembly of the cups is tightened by the thick flange suitable for the pressure rating.

I may be wrong but with partial description or without understanding the service it is difficult to diagnose.

Thanks anyway but this is not for maintanance purpose.This is for design using a tech that i am not the first to use as you indicates.-