dear syam,
Reformer tubes it self they are using alloy steel tubes.incol in not a manditory for this temperature.
thanks
satya
On Thu, 14 Aug 2008 Shyam Herur wrote :
>Thanks for the reply and the inputs.Regarding the valve material, if such
>high temperatures do exist in the steam list we are likely to change it to
>Inconel600 or better.
>
>Shyam
>
>On Mon, Aug 11, 2008 at 2:19 PM, <kannan.sundaram@linde-le.com> wrote:
>
> >
> > Though such high temp valves do exist, but few in the plants and are
> > specialized construction, due to the temp/press and service and the location
> > of the valve and safety requirements.
> >
> > The extended bonnet construction is one option to dissipate heat and to
> > lower the heat at the stem packing similar to the reduction of cryogenic
> > valve temp propagation to the stem packing and to avoid subsequent failure
> > of the packing and operation of the valve. In all, the subject of concern is
> > the stem packing failure. Other options are finned bonnet constr, stem
> > packing with separate cooling system.
> >
> > Protection for valve handwheel operation is not a major concern as it can
> > be chosen as Motor/Pneumatic operated valve. Most of the hand operated
> > valves requires once in a year operation in such high temp service.
> >
> > Coming to the stem packing,
> > 1)The usual ones are in one or more combination of graphite, metal rings,
> > Elastomer rings, Lip seals, simple TEFLON rings etc.
> > 2) In the moderately higher temp. range, only Graphite+alloy is used in
> > diff. arrangements.
> > 3) For very high temp such as your case, cooling system or the extended
> > bonnets and same as 2) packings are used. Also many new proprietary packing
> > arrangements are available in the market. Evaluating them is an important
> > part of a material engineer's role.
> >
> > Additional one to be noted is, the valve basic design is also to be
> > reviewed. Process engr. is not a valve specialist. So the material engineer
> > is supposed to evaluate such cases. In this case a rising stem valve type
> > design to be avoided as it has vertical and rotation wearing on the packing.
> > For controlling a butterfly valve could be evaluated. For Gate types, a
> > knife gate valve could be thought of. Pl. take note that such evaluation
> > has many things to be accounted for such as leakage allowance, emission,
> > hazops, ATEX concerns, operation difficulty, trim erosion and not the least
> > process parameters like pressure drops, zigma allowance, opening/closing
> > period, service fluid etc.
> >
> > Coming to your question,
> > 1) Parameters controlling the bonnet height ...depends on the stem packing
> > design and heat propagation to the packing. As a thumb rule for alloy
> > constr. 250mm shall be the min. height.
> > 2) On tests....apart from the usual tests, service condition test is
> > required to be performed. But if the manufacturer has a prototype test
> > certificate, it could be accepted. Again it depends on the application of
> > the valve. In your case prototype should be OK, in my opinion.
> > 3) Create these valves as special parts and specify the individual
> > condition of operation and design to ensure correct valve/packing design is
> > offered by manuf.
> >
> > *****
> > Important note is the temp you specified and the valve material specified
> > does not go well together. Being a HP steam and at 700 deg. c(which itself
> > is very unusual), SS is no good and it has to high alloy grade. Or your
> > design condition is to be verified. B16.34 defined the temp. limits in the
> > notes of every rating table.
> > *****
> >
> > Regards,
> > Kannan.
> >
> >
> >
> > *"Herur Satyanarayana Shyam \(External\)" <
> > SatyanarayanaShyam.Herur.Guest@snamprogetti.eni.it>*
> > Sent by: piping_valves@yahoogroups.com
> >
> > 11/08/2008 10:03 Please respond to
> > piping_valves@yahoogroups.com
> >
> > To
> > <materials-welding@googlegroups.com> cc
> > <piping_valves@yahoogroups.com> Subject
> > [piping_valves] extended bonnet valves for high temperature service
> >
> >
> >
> >
> > Dear friends
> >
> > I have a query related to valves used at very high temperature for the
> > refinery in Russia Im working on. The service are high temperature
> > hydrocarbon, process with hydrogen or hot air and high pressure steam with
> > ratings of 300# and 2500#. Design temperatures(stream list not yet issued by
> > process) in FEED contractor piping class are 700 to 750 degC. Valve
> > material(CF8, C>0.04)The FEED contactor has put a note against the
> > valves(gate and globe) in his pipng class ' *valves shall be supplied with
> > extended bonnet and heat dissipating elements to obtain a packing
> > temperature of 450degC maximum*'. We have come across extended bonnet
> > valves for cryogenic service.I would like to know if members have experience
> > with extended bonnet valves for high temperature service. What are the
> > parametres to be considered by the vendor in deciding the height of the
> > bonnet? What are the tests/set up to be performed by the vendor to
> > demonstrate that temperature at packing is <450°C.Is it feasible to have a
> > extroordinarily long bonnet in order to maintain T<=450 deg C?? What are
> > the other packing materials other than graphite that can be used to
> > compensate for the height of the bonnet. line gaskets are spiral wound with
> > SS304H windings and mica/graphite filler.
> >
> > Regards
> > Shyam
> >
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