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 Read More Threads Like This OneLucycn (Industrial)

what is different between flanged and double flanged?NGiLuzzu (Mechanical)Lucy,   I think they mean the same thing, i.e. a valve body with two flanges for connection to piping (even if I saw a valve with one flanged end and a butt-weld one, once... but it was quite an oddity).     Bye,   'NGLLucycn (Industrial)Hi anegri,Thanks for your explanation, I have the same feeling for the one flanged end, but I received a questionary, it list 4 types of Double Eccentric butterfly valve ( Wafer, Lug, Flanged and Double flanged), 5 types of Central line (Wafer, Lug, Flanged, Double flanged and Metal-Metal) 3 types of Triple Eccentric, Dose it have different?NGiLuzzu (Mechanical)Lucy,     my feeling is that the questionary refers to the products range of a specific valve Manufacturer. In fact, whileflanged" regard valve ends, "Metal-Metal" regards valve seat... and I know, for example, that exist Manufacturers whot produce metal-seated triple-eccentric butterfly valves only, but in all types of end connections.     So I don't know what the difference between "Flanged" and "Double flanged", in this case, could be; of course, I'd suggest to ask the Author of the questionary, if possible.         Ciao,      'NGLLucycn (Industrial)Hi Anegri,Thanks for your clear division,as you mentioned you knew the exist manufacturers who product all types of end connection of metal seated triple-eccentric butterfly valve. does it has other types of end connection except Wafer, Lug and Flanged? does it has the rubber seated of triple-eccentric butterfly valve? or only metal seated triple-enccentric butterfly valve existed?tsenthil (Mechanical)Most of the triple eccentric Butterfly Valves are metal seated  (I Saw some eccentric valves with PTFE seat). This is because Triple Eccentric Butterfly Valves are primarly used in High Pressure and High Temperature areas where operating torque of Valves are more.

Flanged end and Lug end valves are same. 

SenthilRXH (Mechanical)

Both mean the same. However, "double flanged" is commonly used in the butterfly valve industry to distinguish between the normal "double flanged" valve (two flanges, one on either side) from the "lug-type" which has a "single flange" in the center.Lucycn (Industrial)Hi tsenthil,Thanks very much for your response, Yes, Most triple eccentric butterfly valve is metal seated, does it can be no leakage? How about the PTFE seated? did you see some eccentric valve using a pack of blade of steel and graphite on the disc or on the body to guarantee the absolute and perfect sealing?You mean "Flanged end and Lug end are same valve" But "Double flanged end should be different with Lug end"?

Thanks in advance.Lucycn (Industrial)Hi RXH,Thanks a lot for your further explanation, as you mentioned "both sean the same" it is means" Flanged end is the same with Lug end"? but Double flanged is different with Flanged?tsenthil (Mechanical)1. Some valves like Durco BX6 Series Metal seated valves meet ANSI FCI 70-2 Class VI leakage.

2. Normally all PTFE Seated valves are Class VI Tight Shut Off valves.

3. Double Flanged and Lug (Flanged) Valves are different. Double Flange has two flanged on both edges of valve body whereas Lug type is having single flange in the center of valve body.

Normally Valves designed in AWWA standards are Double flanged type. This valves are very large in size (above 900mm to 2000mm) mainly used in cross country water pipelines.

Flanged or Lug type valves are manufactures as per API609 or BS5155 and normally sizes varies from 50mm to 700mm.

Lucy:

I dont know about valves you have mentioned Graphite etc., but Generally Metal Seated Butterfly Dampers are with Inconel or SS Seats and they achieve 100% Sealing by using a Seal Air Fan.

Generally Graphites are used as Seals if the valves are Fire Safe in design.

Thanks

SenthilLucycn (Industrial)

Hi Senthil,Thanks a lot for your reply.1. I am not familiar with Durco BX6 series valve, where can I find it? what types does it belong to?

2. what different between PTFE seated and EPDM seated valve? Do I distinguish it only from different appliciation? does their different has other meaning?

3.the flange thickness of AWWA standard usual is thicker than DIN standard. what different it is in appliciation?

I just heard of the valve using a pack of bladeof steel and graphite on the disk or on the body to guarantee the absolute and perfect sealing. but I never seen it.NGiLuzzu (Mechanical)Lucy,      as far as I know, rubber seated butterfly valves have usually single- or double-eccentric design and are usually used in water services (or similar), while triple-eccentric ones are usually metal seated. "Metal seated", however, does not exclude the presence of "soft" parts where graphite (or PTFE, depending on service conditions) is present: spiral wound gaskets, stem packing and seal.      Many triple-offset metal-to-metal valves (like Vanessa Series 30,000 by Tyco, for example) have a seal ring mounted on the disc and the seat on the body, hard faced with Stellite,Inconel, Ultimet, etc.; the seal ring is usually of a lamellar type, i.e. made of alternate lamellas of metal and graphite (or PTFE). Depending on the service conditions (high temperature, solid particles, etc.) a "solid", all-metal seal ring is also used. Both can achieve very good sealing performances, such as "Class VI" for control valves or "Zero Leakage" (even if this expression should be avoided: see      Hope this can be useful...          Bye, 'NGLLucycn (Industrial)Hi anegri,Thanks very much for your explanation.

Dose rubber seated butterfly valve is only usded in water services and similar? can you tell me more about "similar"? Dose triple-eccentric metal seated can be used in more application?Dose triple-eccentric is the same definition with triple-offset? or difference?Your explanation about seal ring of triple-offset M-M valve(like valve by Tyco,for example or like valve by Adams, for example maybe) is clearly and very useful for me, even I never seen but I think I can understand what you said, and it is also same with my customer explain to me.Thanks again.lms1964 (Mechanical)

how triecntric geometry is achived in triecentric metal seated butterfly valvesNGiLuzzu (Mechanical)Lucy,       rubber-lined valves, of course, have more thermal and chemical limits, but I don't know many applications, more then water related ones.       Metal-to-metal valves, instead, are fire-safe and can be configured for many services (in the chemical, geothermal, food, mining, water, power generation, oil and gas industries...).         Yes, for me "triple offset" is the same as "triple eccentric".        Maybe the following links can be useful for your information, just to see some images of this type of valves:   *          http://www.vanessavalves.it/   *          http://www.fc-x.com/orton/   *          http://www.tomoeeurope.com/products.cfm   *          http://www.velan.com/products/catalogs/bf.htm                   Best regards, 'NGLHmmmmm (Mechanical)

Lucy:

Your initial question about the flanging seems to have exploded to many other subjects. I will try to give you answers to whatever I remember from the above thread...

Re. flanged and double flanged concept. This means the same thing, i.e. the valve has a flange at each end. A specifically single flanged valve is generally considered a lug type valve. Lugs are typically tapped to allow the valve to be bolted between the pipe flanges from both ends. I have come on ocassion across a spec that described a single flanged valve as a valve with lug body, but drilled through, not tapped, which functioned as a wafer body, but still allowed simple bolting to a dead end without a redundant downstream flange.

Re. differences between flanged (i.e. double flanged) and a lug or wafer. Here you have to be careful, the laying length i.e. face to face dimension of a flanged valve is significantly wider than of a lug or a wafer valve.

Re. rubber seated, metal seated, Teflon seated, graphite laminates, etc. butterfly valves. These are all very different animals, for different applications, and the costs differ significantly.Commercial type rubber seated BFV would be the low cost end and a metal seated triple offset valve like the one with the stainless and graphite laminated disc seal you mentioned above, would be on the high end of the price ladder. However, the applications of these valves can overlap, so your selection should, amongst other, be governed by cost considerations. Generally, rubber seated valves are good for low pressure (250 psi max) service, and low temperature (300 F max) for very vast selection of flow media, depending on what rubber is used. Teflon lined valves can either be plain zero offset valves same as the rubber seated valves, except these valves are suitable for more corrosive service than rubber seated valves; or they can be double offset or even triple offset hi-performance valves for higher pressure and higher temperature service. Pressure is more or less unlimited, and temperature is limited to somewhere between 400 and 500 F, depending on the fill in the Teflon material.Metal seated butterfly valves can be either damper type (somebody mentioned) with leakage rate varied usually by the valve size (very difficult to get a small damper to conform to a low leakage rate); or metal seated valves can be double or triple offset type. Double offset metal seated valves are usually used together with Teflon seats and are the so-called common fire safe hi-performance valves. Triple offset metal seated valves are of various construction, but in most cases, use a laminated seal ring, either on the disc or in the body, to seal against very high temperatures and very high pressures. Triple offset metal seated valves are inherently fire safe, and inherently cryogenic (with neck extension). Contrary to what was stated by someone above about class VI leakage rates, reputable manufacturers produce triple offset metal seated valves to perfect bubble tight seal. Triple offset valves are normally not used in corrosive applications, and would be an overkill in a plain water application. Typically, high temperature service like steam would be the common use for triple offset BFVs.

Well, I hope this is enough for now...Good Luck...

Lucycn (Industrial)Hi Ims1964,Thanks very much for join our topic. wish some experts can answer your question and wish you can learn more from here as I do.Lucycn (Industrial)Hi anegri,Thanks for your further explanation for rubber seated and metal seated valve. I have another question about metal seated valve. As you mentioned, metal-to-metal valve is fire-safe can be configured many service. Do all Metal-to-metal valves are fire-safe? what's meaning of fire-safe? if all metal-to-metal seated valves are fire-safe, why my customer must require me to provide fire-safe certification?How can I get this certification?Thanks a lot, wish my question does not beyond our topic.Lucycn (Industrial)Hi hmmmmm,Thanks very much for your browse all of our comments to give me your idea about my initial question. 1. flanged and double flanged. yes your explain make me more clear of it, but I still have a question from your answer, what's different from drilled through and tapped? as I understand whether drilled through is usual used in bigger size, tapped used in the small size? if for high pressure i.e. PN40 and up, whether flanged (lug type) can not support valve sometimes? so the double flanged maybe better?2. yes double flanged face to face dimension is wider than lug and wafer valve. how can I to distinguish them? as I know for centre butterfly valve is lug and wafer valve, for eccentric( double or triple) is more double flanged (some times is wafer)but for bigger size almost all of them are double flanged. what are they different? just from cost and application? how can I suggest to use eccentric valve to instead of center valve( in what condition can I suggest)?3.if triple offset metal seated valves are inherently fire-safe? Do I need to provide the certification of fire-safe for my customer? How can I get this certification? as the same question I mensioned above?4. does the bubble tight is the same meaning with no leakage? what's different of them?5. Now I am clear of the use of Rubber seated Teflon seated and Metal seated butterfly valve. Thanks again.

NGiLuzzu (Mechanical)

Lucy,      as you can probably see by looking into the above mentioned websites, usually Manufacturers are already fire-proof certified, that is they have already performed "prototype" fire testing on a set of valves able to qualify a certain products range. Otherwise, they can perform fire tests upon Customer's requests, for single projects... so, of course, I suggest you hear from your Manufacturer to get certification.   The usual reference standards are API 607 (this is intended for rubber-seated butterfly valves with a certain maxmum allowable leakage, but it can be also extended to metal-seated ones by accepting "no visible leakage" only, for example) or similar API 6FA and

lms1964,      about achieving triple-eccentric geometry, I think that the first two offsets regard the shaft axis, while the third is provided by the conical machining of the seat on the body.

              Bye,    'NGLHmmmmm (Mechanical)

Lucy:

Here are answers to your questions from Aug. 5th.

1. tapped and not tapped flange holes in valve bodies. Generally, lug version of the body has tapped holes, which allowes direct bolting to pipe flanges without using nuts. On rare occasions, customers try to avoid tapped holes, because stripped threads are difficult to repair, so they may ask for lugs to be drilled through for bolt clearance, and use longer bolts or studs plus nuts to install the valves.Flanges are always drilled through. PN 40 (40 bar) is not considered high pressure for lug-bodied valves.

2. distinguishing valve construction by bodies, flanged versus lug, for example... this is done by visual inspection, of course. You can see whether the valve is flanged, or lugged, or a wafer etc. just by looking at them.Whether a butterfly valve is zero offset, or single offset, or double or triple offset requires more expertise, but here are some rules of thumb:Zero offset valves are typically fully lined rubber or polymer seated valves, with symmetrical disc and the shaft in the middle of the disc.Single offset butterfly valves have shaft on one side of the disc, i.e. the disc is not symmetrical, and are almost always soft seated, i.e. rubber, or PFA clad rubber seats. Larger valves may have adjustable seats. These valves are mostly used in waterworks applications.Double offset valves look like single offset valves, except they typically use a thin polymer not-adjustable seat.Triple offset butterfly valves are almost exclusively metal seated, have a funny looking skewed disc edge and corresponding funny looking seat geometry. Typically, there is a lot of cap screws holding down the disc seal and the seat inside the valve, that right away signals a metal seated triple offset valve.To my knowledge, size has nothing to do with the body type, there are very small flanged valves say smaller than 1", and there are very large lug-bodied valves, say 72". Wafer bodies tend to vanish past 48" size, because the wafer body becomes too flimsy to hold precisely the internal dimensions.

3. Manufacturer has to produce a certificate that the valve has been tested to a recognized fire safe standard, such as API 6FA mentioned above by Anegri. API 607 firesafe spec is for soft seats, and therefore theoretically does not apply to triple offset valves which have hard seats. However, manufacturers of triple offset valves sometimes test to API 607 and produce certificates to this spec, claiming that their metal seal is to a certain degree flexible, and hence the seat is "soft". For butterfly valves, it is easier to pass API 607 than API 6FA.

4) Bubble tight means what is says: no bubbles across the closed valve when tested with soap or under water with a gaseous test media, i.e. completely leak tight.

Lucycn (Industrial)

hi anegri,Thanks for your suggestion and the website you had provide for me, I had browse their website, most of them have the fire-safe certified, as manufacturer we also can provide according to customer's request and test conform to API607, API 607 Incl. fire-safe test API 607 4th version and triple offset test with zero leakage,does it is the similar with API 598 for test with zero leakage? I am not familiar with API 6FA and ISO 10497 it is the similar with API 607 and API 598? all of them is test with zero leakage? what's different with them? how can I choice when I have to test triple offset butterfly valve and double offset butterfly valve?Thanks.Lucycn (Industrial)

hi hmmmmm,Thanks for your patient explanation for my question.1. the wafer type is the same like Lug has the tapped hole not drilled? How much pressure as usual can be withstanded for wafer and lug type valve?2.Beside of distinguishing valves from construction by bodies,cost and applicable medium? can I use double eccentric to instead of centre butterfly valve?Lucycn (Industrial)

Hi hmmmmm,3. Can you tell me more about the different between Single offset with double offset? does it only distinguish from adjustable seat or non-adjustable seat?4.most triple offset is matel seated does it can test conform to API 607? is there any other standard is suitalbe for triple offset matel seated?Hmmmmm (Mechanical)

Lucy:

More answers to your latest questions:

1)Wafer bodies are smaller on OD than lug bodies, (the of a wafer OD would be about like the inside of the flange bolt circle), the flange bolts straddle the outside of the body. You can not bolt a wafer to a single flange - wafer is squeezed between two pipe flanges.Lug body has either a large OD (the OD would be about the same like the OD of the flange), or it has protruding lugs to facilitate flange holes. Lug bodies can be bolted to a single flange at the end of the pipe.

2) Yes if compatible with the application conditions...

3) Single offset places the valve stem on one side of the disc, thereby ensuring uninterrupted sealing surface in contact with the seat. The problem is that the disc touches the seat all the time. Even when the valve is open and the disc is out of the seat, its edge touches the seat at two locations. The disc must be bigger than the seat to seal, hence in a single offset valve that has been open for a long time, the disc digs two impressions into the seat where it was in contact with the seat. Rubber seated valves can tolerate this condition, because rubber will readily flow into the depressed areas and seal the valve upon closing. However, polymer seats and other harder seats can not react so elastically as rubber. Hence, a single offset valve with polymer seat would leak at two locations after it has been closed following a longer period of being open. Here is where the second offset comes in. The second offset is designed such that it places the valve stem not only on one side of the disc, but also a bit sideways, thereby ensuring that after the valve has been open, the disc edge clears the valve seat, and thus does not produce damaging impressions. The second offset is minimal, only enough to clear the seat. Dimensionally, for example, in a 12" valve, the first offset would be say 1.5 inches, second offset would be 60 thou. Second offset introduces offset torque, which tends to open or close the valve, depending from which side the pressure is applied. This torque may be very significant in larger valves.

Adjustable seats are used only for larger rubber seated single offset butterfly valves. I have not seen a double offset valve with adjustable seat.

4) Hard seated valves like triple offset should really be fire tested to API 6FA. Like I wrote before, API 607 is for soft seated valves, i.e. zero, single, and double offset valves. But almost all manufacturers of triple offset valves claim to have certified the valve to API 607. It is easier to pass API 607 because it allows leakage and is limited to only 30 psi, and that is probably why this test is more popular with manufacturers.By the way, API 598 has nothing to do with testing for firesafe capability. It deals with hydrostatic tests of  valves and with leakage tests across the seat.

Lucycn (Industrial)Hi hmmmmmm,Thanks for your more answers to my question. I think as more experiences as I have I will clear what you said, it will be very useful for me.if possible I would like to ask you other question about butterfly valves.1. Would you tell me what's different between the centre butterfly valve with pin and without pin? does it only come from centre butterfly valve or also appeared in single and double offset butterfly valve? 2. would you tell me what's different for double offset butterfly valve that the rubber seal is setting in the body with setting in the disc? what's different request for the applicable medium?3.which one have longer application between double offset and triple offset.Thanks a lot.Hmmmmm (Mechanical)

Lucy:

1) I am not sure what you mean by the "pin". Pins are often used to secure the disc to the valve stem. This feature is used on all types of butterfly valves. No pins would mean that the drive between the disc and the stem is internal to the disc, such as an internal square, DD flats, splines etc. Internal drive is considered better than pins, especially in the zero offset resilient seated fully lined valve category, because the disc to stem connection is protected from the flow media.

2) I don't understand the question...

3) Life of a valve always depends on the severity of the service. Triple offset valves are usually used in different applications than double offset valves, and vice versa, so the comparison between the length of usefull service valve is not realistic. However, the triple offset metal seated valve would have wider rande of applications and longer life than double offset valve in many high temperature non-corrosive applications. Double offset valve would be less expensive and possibly work better than triple offset in applications involving mildly corrosive and erosive service in lower temperatures. Metal seated triple offset valves are becoming more and more popular as the price comes down with improved manufacturing methods and stiff competition.

Lucycn (Industrial)

hi hmmmmm,1.Yes, You have good understand for my question, pins are often used in secure the disc to the valve stem. I just notice that it is on the centre butterfly valve disc. I will observe other butterfly valve how the disc to stem connect is protected from the flow media.What's meaning of DD flats?2. I mean what different between the seat is mounted on body with on disc?(double eccentric rubber seated butterfly valve, the rubber seat is mounted on the body or on the disc?) which one is better? does it distinguish from the media? 3. Refer to drinking water(I mean general temperater and general pressure condition) which one is better double offset rubber seated butterfly valve and double offset metal seated butterfly valve?Thanks a lotHmmmmm (Mechanical)

Lucy:

1) Double D flats are just two opposing flats machined to the round shaft. I guess the material removed would have a geometry of two Ds back to back, hence the double D name. 

2) Seat is always in the body... Disc may have a separate sealing element attached to the disc edge, and sometimes, such a seal element is called a seat. Not exactly the best way to say it... If the seat or the disc seal are resilient and soft, like rubber, then the seat in the body is considered better design than seal on the disc, because the seal on the disc is exposed to the full velocity of flow, and hence it can get eroded by the flow relatively easily.The seat in the body is at the boundary of the flow way, and hence the erosion is not as severe.

3) In drinking water, with normal temperatures and pressure, you should look for a zero offset fully lined rubber seated butterfly valve, or possibly a single offset rubber seated valve. Anything else is in my opinion an overkill... Certainly not triple offset valve...Lucycn (Industrial)

Hi hmmmmm,Thanks a lot. I will choose rubber seated attached on the body in the future, I think.Refer to seat is on the body, would you tell me what's a separate sealing element attached to the disc edge?what's the advantage and disadvantage in character between double offset and triple offset butterfly valve? i.e. the torque, friction, etc.Thanks in advance.Hmmmmm (Mechanical)

Lucy:

In certain type of butterfly valves, there may be both replacable seat in the body, and a replaceable seal ring on the disc edge. Triple offset metal seated valves are a good example. Typically, both the seat and the disc seal ring are replaceable (exception is Vanessa who weld stellite seat into the body and it is not field replacable).

Lucycn (Industrial)

Hi hmmmmm,Thanks for your reply, Sorry for response later, my computer contract Virus Worm.Blaster from Aug.11, I cannot log onnow. Refer to my question I think I am clearly, but I wish to keep continue discussing this topic when the problem I meet in my work in the future.Thanks for all the people who joined our discussing. Thanks anegri, tsenthil, RXH, Ims1964...