Sorry if there's another post relating to this. I searched but couldn't find any. The vast majority of chemcial sites that i've been to or worked at use flagned 150# stainless ball valve with some form of soft seat for process lines. One site I visited is using plug valves for process instead of ball. No one could give me a good reason for why they're using the plug vs ball. Can anyone give me their 2 cents on why you would use one over the other?
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Ball Valve Vs Plug Valve Process 2
- Thread starter NCENG78
- Start date
Plug and ball valves are quite similiar; a ball valve can be considered a spherical plug valve, just as a plug valve can be considered a conical ball valve.
Ball valves have to be removed from the pipeline for maintenance, unless they are top-entry valves, which are expensive. The cone inside the plug valve is less likely to require complete removal for maintenance.
Ball valves disrupt the flow of the medium less than other types of valves, but the flow cannot be changed; plug valve flow, however can be changed by changing the size and shape of the plugs and seats. Plug valves are, moreover, more cost effective on high pressure applications; ball valves can also handle high pressure, using the trunnion configuration, but as in top-entry ball valves, trunnion mounted valves are more costly than standard valves.
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Ball valves have to be removed from the pipeline for maintenance, unless they are top-entry valves, which are expensive. The cone inside the plug valve is less likely to require complete removal for maintenance.
Ball valves disrupt the flow of the medium less than other types of valves, but the flow cannot be changed; plug valve flow, however can be changed by changing the size and shape of the plugs and seats. Plug valves are, moreover, more cost effective on high pressure applications; ball valves can also handle high pressure, using the trunnion configuration, but as in top-entry ball valves, trunnion mounted valves are more costly than standard valves.
Corrosion resistant, exotic alloy valves from The Alloy Valve Stockist in Barcelona, Spain [URL unfurl="true"]http://www.gate-valves.com[/url]
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- #3
I have a bit different spin on this.
In the 1960's all block valves were variations of the gate valve. Plug valves came on the market late in the decade and were actually 1/4 turn operation instead of dozens of turns. Many companies changed their standards to allow plug valves very quickly--in the 1970's we tended to treat company standards as something that should keep up with technology.
Ball valves became commercially available in the 1970's and were clearly better for any moderate temperature application. They require a lot less maintenance, have a more reliable seal, and can be piggable. By the 1980's companies that still felt that their standards should reflect evolving technologies embraced ball valves and deleted plug valves for non-steam service.
The generation of Engineers that was leaving industry by the mid-1980's had a different view of the profession that the Engineers that were coming behind them. The next generation often viewed standards as unchanging and monolithic; nearly sacred. "Who am I to question the standards?" Any standard that hadn't been changed by 1995 was pretty much doomed to keep plug valves as the primary block valve. We have a pipeline company where I live that still requires plug valves in the field, and their Engineers defend that choice with vigor even though their field operators dearly hate them. The problem with plug valves is that they have to be regularly serviced. In my industry (Oil & Gas) field valves are [mostly] never serviced. A plug valve sitting in a valve can, covered in mud and water for a decade or so without being operated or serviced will not budge when called on to close.
I have never seen an objective reason to prefer plug valves over ball valves in moderate temperature service. The service-in-place argument that I often here is really not germane to my industry since we never repair valves in place (if we repair them at all it is a swap-out and fix it in the shop because we don't want production stopped while futzing with a valve, usually we just scrap a problem valve).
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
In the 1960's all block valves were variations of the gate valve. Plug valves came on the market late in the decade and were actually 1/4 turn operation instead of dozens of turns. Many companies changed their standards to allow plug valves very quickly--in the 1970's we tended to treat company standards as something that should keep up with technology.
Ball valves became commercially available in the 1970's and were clearly better for any moderate temperature application. They require a lot less maintenance, have a more reliable seal, and can be piggable. By the 1980's companies that still felt that their standards should reflect evolving technologies embraced ball valves and deleted plug valves for non-steam service.
The generation of Engineers that was leaving industry by the mid-1980's had a different view of the profession that the Engineers that were coming behind them. The next generation often viewed standards as unchanging and monolithic; nearly sacred. "Who am I to question the standards?" Any standard that hadn't been changed by 1995 was pretty much doomed to keep plug valves as the primary block valve. We have a pipeline company where I live that still requires plug valves in the field, and their Engineers defend that choice with vigor even though their field operators dearly hate them. The problem with plug valves is that they have to be regularly serviced. In my industry (Oil & Gas) field valves are [mostly] never serviced. A plug valve sitting in a valve can, covered in mud and water for a decade or so without being operated or serviced will not budge when called on to close.
I have never seen an objective reason to prefer plug valves over ball valves in moderate temperature service. The service-in-place argument that I often here is really not germane to my industry since we never repair valves in place (if we repair them at all it is a swap-out and fix it in the shop because we don't want production stopped while futzing with a valve, usually we just scrap a problem valve).
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
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