Steve,
Thanks for the complements. Once upon a time, I was a
lecturer in Engineering College. Probably, the skill
acquired over there, worked well in explaining the
picture.
My context was precisely, a fertilizer plant.
Regards.
Gangadharan.
--- Steve McKenzie <mechproj@xtra.co.nz> wrote:
> Wow
>
> thanks for that Mr Gangadharan.
>
> Just so I am clear, the gasket is shaped like a
> convex optical lens
> (obviously with a hole in the middle) and the
> sealing faces are part of the
> pipe and concave cone faced . But the pipe is
> overthickness so the joint
> tensioning flanges can be screwed on to it.
>
> What a monster! I guess thats about as good as it
> gets.
>
> I have two questions:
>
> 1) Does the flange you describe look like the one on
> the compressed air line
> under discussion?
>
> 2) With such an excellent descriptive style, why are
> you not writing patent
> applications instead to trying to help us lot?
>
> I sat down with pencil and paper and drew line by
> line what you described
> and it came out perfectly. Normally I wind up with
> something that looks like
> Mickey Mouse.
>
> I still do a bit of work in fertiliser, but its
> superphosphate from rock+
> sulphuric acid , so the enemy is fluoride corrosion
> but pressures are
> manageable.
>
> Thanks again
>
> Steve
>
> -----Original Message-----
> From: Gang Cvg [mailto:cvg_gang@yahoo.com]
> Sent: Thursday, February 05, 2004 9:10 PM
> To: PipingDesign@yahoogroups.com
> Subject: RE: [PipingDesign] flange failure
>
>
> Steve,
> Topic of LENS gasket.
> My field of working in the past (nowadays I work for
> hydrocarbons) was detailed engineering for
> fertilizer
> plants. I knew the use of lens gaskets from the
> early
> seventies.
> The application was in high pressure (PN 160 and PN
> 320 in the DIN specification) for the highly
> corrosive
> urea and ammonium carbamate (by default, liquid
> ammonia also) solution lines, where almost all known
> materials had failed; and the leakage from flanges
> was
> a perennial problem. I do not wish to mention the
> process licensors for these projects. I cannot say
> that the lens gasket was the ultimate solution. The
> fact remains that it used to be very effective
> against
> the leakages. For the ratings below and for PN100,
> the
> conventional type of gaskets was used.
> Now, coming to the point; what really makes the lens
> gasket sought after? The answer is that in the good
> old days, the urea synthesis pressure used to be in
> the range of 250 bar and in the environment of
> severe
> corrosion. Nowadays, by the improvement in
> technology,
> this level has been brought down to a very
> reasonably
> manageable level, wherein, conventional gaskets are
> effective. That could be the reason that this topic
> is
> looking to be new to many pipers.
> Let me explain the structure of a typical lens. I am
> avoiding the use of a sketch. The mating pipe ends
> (nozzles) have a wall thickness in excess of the one
> required for withstanding the internal pressure.
> This
> extra is kept for the threads to be cut on the outer
> surface. The threads engage on a pair of collar
> flanges with the studs on either side. The outer and
> the inner diameters of the lens are the same as
> those
> of the pipe, with a vertex formed at the outer tip.
> The surface of the gasket is such that both the
> external surfaces have a spherical contour with
> their
> centres lying on either side (opposite) along the
> axis
> of the pipeline; with radii large enough to lave a
> delta type cross section at the rim. The surface
> finish is that of a triple delta or lapped one.
> Extreme care is observed while handling the gasket
> so
> as not to cause any scratch or score on the surface,
> due to any reason. The pipe end, a pair of special
> nozzles made for the purpose has a reverse bevel
> surface that too with the same quality of surface
> finish. When both of them are brought together,
> literally, the contact is over a line, a sphere
> meeting a hollow cone, that too over a super finish
> texture, at both the contact faces. When the studs
> apply pressure, during tightening, contact stress is
> theoretically, infinite. That seals the leak. This
> is
> the secret of a lens gasket. Obviously, the material
> used to be special urea grade stainless steel.
> Looking back on the sealing philosophy, to have an
> effective sealing pressure, we should have 1.5 times
> the system pressure at the contact face. The purpose
> of having less and less contact area from a low
> rating
> towards the high pressure, is through, a flat
> gasket,
> then a raised face, still further, are the tongue
> and
> groove, male and female, double male and female,
> ring
> type joint. The lens is the highest end. A similar
> situation exists in equipment (particularly, heat
> exchangers) body seals as delta gaskets. The bolt
> circle has a limit to manageable levels (which
> contains the number of studs) and the stud size is
> another factor, which limits the external FORCE
> applied to achieve a closure. That means we are left
> with only one option that is to reduce the contact
> width of the gasket.
> All the components (except the flange and studs) in
> this case are made of special urea grade stainless
> steel.
> I hope the matter has been well explained. If anyone
> has got further doubt, please do mail back to me.
> C. V. Gangadharan, located at Athens.
>
>
> --- Steve McKenzie <mechproj@xtra.co.nz> wrote:
> > No worries
> > I am not familiar with lens type flange
> description.
> > Google refers me to
> > cameras. I think it probably has a concave
> spherical
> > load bearing surface
> > but am unsure. Could you (or someone) please
> > explain?
> > Your understanding of this site is the same as
> mine.
> > To share experience in
> > a professional way requires a full description of
> > the problem; its unclear
> > questions that waste time.
> > Hope you got it fixed.
> >
> > Cheers
> >
> > Steve
> >
> > -----Original Message-----
> > From: Lakshmi V. Narayana
> > [mailto:LNarayana@safco.net]
> > Sent: Saturday, January 31, 2004 6:08 PM
> > To: 'PipingDesign@yahoogroups.com'
> > Subject: [PipingDesign] flange failure
> >
> >
> > Dear friends,
> > Sorry every body. yesterday off for me,Line size
> 12"
> > is going reactor 2
> > transfer PIPE was jerking due to uncontrolled of
> > pressure.Flange is lens
> > type SS 304.
> > To my knowledge this site is concerned to share
> > our experiences in
> > proffessional way.Please do not get tense. If i
> > wasted your invaluable time,
> > I am very sorry.
> > Thank you very everybody for giving reply.
> >
> > Lakshmi narayana
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
=== message truncated ===
This archive was generated by hypermail 2.1.8 : Mon Oct 27 2008 - 20:24:02 EDT