Friday, August 29, 2008
Ball valve soft seat materials and temperature limitation
In general you may refer Table A323.4.3 of ASME B31.3
Bathula Raghuram
Ball valve soft seat materials and temperature limitation
This compilation done by Yayati-TICB. Source: Shell SPE.
Take note this is not an exahaustive list and various brands of PTFE does exist having different limits. So take the advice of the valve manufacturer before detailing your seat spec.
| SEAT MATERIALS | Temperature range (deg.C) | |
| Filled PTFE | -100 | 220 |
| PEEK | -100 | 260 |
| Modified PTFE | -200 | 200 |
| EPDM | -20 | 110 |
| VITON (fluoroelastomer) | -30 | 200 |
| NEOPRENE | -20 | 85 |
| NITRILE (NBR) (BUNA-N) | -10 | 100 |
| STYRENE (SBR) (BUNA-S) | -40 | 70 |
| NYLON POLYAMIDE | -40 | 90 |
| ZYFLON | 0 | 100 |
| POLY OXY METHYLENE (POM) | -50 | 110 |
| DEVLON -V (API GRADE) | -100 | 150 |
| PER FLUOR ALKOXY (PFA) | -100 | 200 |
| ETFE | -198 | 149 |
| PCTFE | -250 | 150 |
| VESPEL | -150 | 150 |
| swapnil gorantiwar <gorantiwar_swapnil@yahoo.com> Sent by: piping_valves@yahoogroups.com 29/08/2008 10:20
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| i want to know the temperature range of non-metallic seat material for ball valves. for which temperature range which non-metallic seat material is to be used in ball valves? |
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Finex and Corex furnaces.
As in the past we found few questions on furnaces and felt to add this to those messages.
Just today I read an interesting second page article in newspaper on Finex furnace which are new generation furnaces without ovens able to operate using fine coal instead of the traditional coking coal which is a high pollutant. Using this furnace the energy cost and pollution is reduced. And yet it does produce the pig iron suitable for high grade steels.
Posco with Siemens, then VAI has developed this in the past 10 years spending heavily and Posco's new plant in India and Vietnam are planned to be build with these Finex furnaces. This is a modification of Corex furnaces as per the article.
They claim the cost is reduced by 10% in overall and as the current fine coal price and coking coal price gap is increasing, they hope it should be more profitable in the coming years.
Good for Nature and Environment and in having a competitive steel price.
Regards,
Kannan.
Thursday, August 28, 2008
PWHT by Induction Heating Method
I understand that in projects like Borouge, Ruwais the main construction contractor CCC is using and are prefering the induction heating. As per my conversation the same as you have highlighted of the prefabrication spooling had been found to be more efficient and less time consuming and very acurate control of temperature, in comparision.
With regard to portability as per the contractor, they are using both portable and as well as fabrication shop stationed machine. It is available on lease by quite a no. of suppliers in the gulf region in particular. I havn't checked out the names of manufacturer nor the leasing agents, but can find out.
CCC also does have its own facility in the region in catering to various project sites of them. So in that sense it could be more efficient and cheaper solution on the run though the initial investment is high.
With regards,
Kannan
Dear members
Please share your experience on the subject method for pipe welds
(PWHT to be carried at site), one of our client insisting for
Induction heating instead of PWHT by conventional resistance coil
heating.
tho' i have seen literature on this I need info on availability (first
hand experience) of the equipment, portability etc..
I understand it is faster but advantageous in mass production, and may
not be easier for site activities. i don't see any reason for this
method over resistance heating
Raghuram Bathula
Wednesday, August 13, 2008
Material discrimination color.
The term is not used in our sector except in the shipping of our materials. Though I am much sure about it, to what I have once heard from a supplier that the containers are scanned like our baggage to know the content without opening, in specific to know if any internationally export banned materials are shipped like radioactive elements etc. The scanner is capable of displaying in diff. colors the materials in the containers. Like steels, super alloys, rare metals in diff. colors. This caused the shippment delay which was how I came to know of it.
With regards,
Kannan
I have one query:what is mean by "Material descrimination color".Is it related to material identification using colors, like cs pipes with one color ss pipes with another color.
Sheetal Patil
Design Engineer(Piping)
Monday, August 11, 2008
Extended bonnet valves for high temperature service
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.
Dear friends
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.
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
Snamprogetti
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