Dear Ranjiit
As far as I know the clad thickness is not brought into the strenght calculation
of the cladded vessel , therefore all the pressure parts should be welded to the
base metal , your case carbon steel.
The other reason which crosses my mind is that , in cladded vessels the internal
fluid in contact with the clad is very corrosive for the outer layer (cs) ,
therefore , if there happens a leak through the clad it will corrode the carbon
steel very fast.For example in Urea Plant the rate of corrosion of carbon steel
in the vicinity of carbamate is 1000 mm per year , so suppose a time this occurs
in your cladded vessel round the tray support attached to the clad , it would
cause support and consequently tray failure.
The welding procedure is also very important while welding the support to the
vessel considering the buttering which is required round the support area which
will be embeded in the stainless steel clad and also PWHT which might be
required.
Therefore I recommend you to follow your client spec.
Hope the above would help
Cheers
Reza
ramanan ranjit <ranjitperu@yahoo.com> wrote:
Dear All,
My question may be classified as an irrelevant one to
this group as it is more or less related to pressure
vessel fabrication rather than piping.However as I
have not find any alternative at present but to ask
this question in this forum. Please forgive me and
allow me to ask this question.
We have a carbon steel vessel which is cladded
internally with stainless steel( the cladding was done
by explosion bonding).Our client specification states
that anything welded to the inside of a cladded vessel
shall be attached to the base metal(carbon steel)after
peeling off the cladding and the area from where the
cladding has been removed shall be filled with weld
deposit.My question is that "is it really necessary to
weld the relative light weight components like tray
support ring to the base metal after peeling off the
cladding which has been integrally bonded to the base
metal by executing a metallic bonding during cladding
operation?Also the bond shear strength of the clad
metal has been established by bond shear test and the
same is many times greater than that required to hold
the tray support ring together with the trays and the
entrained fluid as can be demonstrated by calculation.
On the contrary removal of clad metal will lead to an
area prone to more corrosion in addition to the
undesierable chemistryand hardness produced at the
weld deposited area.
I hope the experienced engineers in this forum will
give more insight to elaborate my above explanation
and in turn help me to convince our client in this
matter.
thanking You in advance.
regards,
ranjit.
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[Non-text portions of this message have been removed] Received on Tue Aug 09 02:36:00 2005
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