What is "Swimming Bowl" in valves??? 5

[TheLucifer]

Hi all,
I have received the following mail from a consultant:

"The reliability of this design is depending on the detailed design of the valve and seals; for example a swimming bowl design could achieve higher reliability than a fixed bowl design."

Frankly, don't know what he speaks about. Does anyone know the difference between swimming bowl design and fixed bowl design?

 

[terje61]

Hello,

I thrust that 'swimming bowl design' is not a bad translation of 'floating ball design'.

Gr.
Terje

 

[JimCasey]

I agree that is sounds like a translation distortion.

 

[TheLucifer]

This seems possible since my consultant's mother tongue is not english.
Then, my second question rises: do floating ball valves really have higher reliability rates? I mean, it seems to me like a fixed valve has a lower probability of leakage than a floating valve, which is pushed downstream with the pressure. Am I right or is there a point I'm missing completely?

 

[Ashereng]

Hard to say.

A floating ball uses line pressure to seal - higher pressure, more force to seal.

What's your pressure?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[code1]

terje61,

Good one on the "thrust". Star worthy

 

[UNSR60001]

Well,

I was inclining not to post anything to the "swimming bowl" question. First, it truly seems like a non sirius question, bordering on a prank. Second the answer is so obvious that does not merit a posting to begin with. ASK YOUR CONSULTANT TO CLARIFY WHAT IS A "swimming bowl design and fixed bowl design"

However if you are talking about Ball Valves. There are basically 3 types.

1. - Floating.
2. - Trunion Mounted.
3. - Rising Stem.

Without going into details regarding what are the benefits or drawbacks of each design. I will like to point out that this statement is deceiving: "A floating ball uses line pressure to seal - higher pressure, more force to seal" While in principle it is true in practice it is false.

It is a fact that the higher the pressure the greater the potential damage to the seats. Therefore the greater damage to the seat the higher leek rate. In turn the higher pressure on damage seats the greater the leek rate. Further more, as a general rule the higher the pressure the lower the performance of non metallic materials.

As far as reliability goes, it is subject to the particular application, considering they are all of sound design. But more importantly is to recognize that there are only 2 kinds of valves good and bad ones. When I say "good Valve" I mean good design, good materials, good manufacturing, and good quality systems. And then in the eyes of the end user it is only "good valve" if it was configured with the right materials and configuration that allows it to perform as a "good valve"

I can’t begin to mention instances that I have been in the field where a Good valve was label by the end user as a bad valve, and in fact it was a perfectly good valve installed in the wrong application. Very few end users of valves will admit this. Even fewer engineers at E&C's will admit they made a mistake when it comes to specifying valves. After all, on/off valves to most people are not important until they need to use it, they seem to think they are just a spool of pipe. They forget why the valve is there to begin with.

 

[gerhardl]

1. On good and bad valves:
I very much agree with you, UNSR60001. Some years ago I was involved in operations supplying large numbers of SS ballvalves general in range 2" 150# - 8" 1500# but up to 36" to North-Sea offshore platforms of one particular brand, with one factory.

Having repeatedly years after been asked why they seem to perform better, with far better lifetime than other brands, I have only been able to come up with one answer: better over-all accuracy and quality in production, with very exact fabrication measurements with slim tolerance in all details, and a general high material quality. No particular design differences from other makes.

I will give you a star.

2. On trunnion mounted ball valves contra floating ball.

One should be aware of one particular application type: With a relatively high onesided pressure on a ball valve for a long periode (years ?), and especially for larger sizes (4" and up?) it would be considered safer for performance quality at critical applications to use a trunnion mounted ball, in stead of floating ball, to avoid cold-floating disfigurement of elastic seals.

 

[TheLucifer]

Thank you gentlemen,
UNSR60001, of course my first reaction was to send an email saying "what does that mean" but the down side of having a "free of charge" consultant is, he may send a confusing idea about design and go to four weeks holiday.

In my application, pressure is virtually zero: only 1 m liquid head. the problem is, valve is a safety valve and should have a high reliability since it will be used for 30 years (with very harsh environmental conditions since it will be installed on an aircraft), with o-ring replacements in every 5 years. Current valve proposal is a fixed (or trunnion mounted) one, and from a respected manufacturer. After your posts and some search, I don't think that a replacement is necessary.

Again, thank you for sharing your experience.

 

[cadymp]

dear UNSR60001,
pl. explain me "raising stem Ball valve" as you stated it as one of basic types.
I was aware of floating ball, trunnion mounted ball & top entry trunnion only.
thanks.

 

[vpl]

...but the down side of having a "free of charge" consultant is, he may send a confusing idea about design and go to four weeks holiday.

He might also answer the question. You won't know unless you ask.



Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

Want to post an image? Look at the FAQ's in forum559

 

[277Peter]

Dear Cadymp

The main rising stem ball valve is the Orbit Valve (now part of Cameron).

See the following link.

http://c-a-m.com/content/vm/prv/index.cfm

 

[UNSR60001]

Cadymap,

Sorry to get back to you so late, unfortunately I don’t have as much time as I would like to enjoy with posting here.

I am very glad that you inquired about the rising steam ball valves. As I am positive that many users in these forums would like to know as well.

Being that said. I would like to take this opportunity to perhaps take several steps back and try to see the subject of valves from a historical and macro perspective. This will provision a broad understanding of valves.

The history of valves is somewhat sketchy, particularly for the period of after the fall of the Roman Empire to the industrial revolution. However there are 2 major known facts:

1. - Valves have been invented and used by humans including some animals from the beginning of time. This is explained by the actuality that a mere object such as a rock that is intentionally manipulated in such a way as to obstruct or regulate a flow path, meets all the criteria of a valve. In the same way beavers also meet these criteria as they manipulate their environment in order to exercise flow control.

2. - In modern times the Romans are accredited for the invention of modern quarter turn valves, the same thing can be said for piping systems. They developed very complex pipe and valve layouts with in the Roman cities.

They are credited for invented the metal valve, which was a lead based Plug valve, consisting in both body and plug in this materials. Additionally they where very adept in designing and using the most rudimentary valve type, the Slide Gate.

In a real way all valves emanate from these 2 fundamental designs. Gates globes and checks all are rooted in the slide gate design. It is easy to understand the evolution from slide gate to any valve that has a disc that lifts.

A gate uses a vertical constructing disc, a globe uses a horizontal obstructing disc and a check uses a hinged obstructing disc.

In the same way it is also easy to understand the evolution emanating from a plug valve to all other quarter turn valves.

An eccentric plug is half a plug. A ball valve is a rounded plug. A C ball is a rounded halve plug. In the case of a Butterfly it can meet both criteria’s because it is an axial gate or a flatten plug.

In this way mechanically speaking you can create a design that would translate into any quarter turn valve into a rising steam one, hence you have rising steam ball and plug valves. At this time I am not aware of a rising steam butterfly or a true rising steam check valve. However theoretically speaking one can be constructed.

There are 2 major drawbacks to designing what I call hybrid valves, meaning lift plugs or rising steam ball valves.

1. - Is the fact that hybrid valves are more mechanically complex, this means higher maintenance and or lower average service life before failure.

2. - More complex valves also mean higher manufacturing cost that translates into larger price tags.

I anticipate the above subject would bring you although brighter and not deep perspective on flow control, however it does help understand some fundamental principles and design criteria of valves.