Stainless Steel Pipe and Tube; is there a difference?

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richardbrennan

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Having succeeded in bowing another mast support pillar, undoubtedly by over tensioning the rig; I need to source a new one and want to go up a size in wall thickness from 2 mm to 3 mm. I am confused by the difference between 316 stainless pipe and tube, is it just the size that determines what suppliers call them, or is there a more fundamental structural difference?
 
As David2452 says. Pipe has a fixed bore with variable wall thickness, normally according to internal pressure requirements. They are known as 'schedules' and Googling will give you the information you want. For stainless steel the schedules are more limited than for carbon steel and you may not be able to find exactly what you want.
 
Not always
Plastic pipe for potable water supply has the same o/a diameter as copper pipe & is called "pipe" by the manufacturers & the critical dims are the external ones. ie 15mm, 22mm, 28mm,etc to tie in with copper tube (or pipe) You do not specify plastic pipe by the internal dimension
But as my old latin teacher often said " it is the exception that proves the rule"
Never understood that. Come to that I never understood his b..dy latin either
 
Dear Vyv/David

Thanks for the swift replies; it's the longitudinal strength that's important in this application so I guess either will do.

Thanks Again

Rick
 
Daydream believer said:
But as my old latin teacher often said " it is the exception that proves the rule"
Never understood that. Come to that I never understood his b..dy latin either
Click to expand...

It's a commonly mis-used phrase. The word 'prove' means 'test' (as in 'rocket proving range') so in this light, the exception is the one which really tests the rule. It has been misappropriated over the years and bent into almost the opposite of what it ought to mean.

[/pedant]
 
Daydream believer said:
But as my old latin teacher often said " it is the exception that proves the rule"
Never understood that.
Click to expand...

Your Latin teacher seemed to prefer mystifying his pupils to educating them. Another word for 'prove' is 'test' (as in 'proving ground', or test track for vehicle development).
It is the exception that tests the rule makes perfect sense.
(The actual origin of the expression is probably legal and more arcane, but this one is both understandable and logical, unlike the normal usage.)

P.S. I see Kelpie overtook me somewhere in the ether...
 
earlybird said:
I think we're getting a bit into semantics here, but, if anything, "pipe" has a fixed OD, not ID as quoted above. Viz BSP thread.
Click to expand...

Eh? BSP sizing is from the internal nominal diameter. '1/2" ' water pipe is around 3/4" OD

Edit. Agree that the OD is fixed, to take the thread.
 
Last edited:
richardbrennan said:
Having succeeded in bowing another mast support pillar, undoubtedly by over tensioning the rig; I need to source a new one and want to go up a size in wall thickness from 2 mm to 3 mm. I am confused by the difference between 316 stainless pipe and tube, is it just the size that determines what suppliers call them, or is there a more fundamental structural difference?
Click to expand...

It's worth pointing out that the resistance of the post to buckling increases exponentially with a modest increase in diameter compared with an increase in wall thickness which gives you only a small increment.You are perhaps limited by existing fittings but you may have room for a larger post.
 
Dear Bluerm

I already went up from a post that was about 6 cm in diameter to one that is about 9 cm; this about as large as I can go without serious surgery to the saloon table. It's my fault the rig was over tensioned and a straight replacement would probably be OK, but I thought I would give myself a little more in reserve by going up from 2 to 3 mm wall thickness. The fabricator that made up the post also suggested that a X piece down the middle would also give extra strength so this might be another option. Sourcing a 2 meter length is not proving to be particularly easy; any suggestions in the Solent area would be welcome.

Many Thanks

Rick
 
macd said:
Your Latin teacher seemed to prefer mystifying his pupils to educating them. Another word for 'prove' is 'test' (as in 'proving ground', or test track for vehicle development).
It is the exception that tests the rule makes perfect sense.
(The actual origin of the expression is probably legal and more arcane, but this one is both understandable and logical, unlike the normal usage.)

P.S. I see Kelpie overtook me somewhere in the ether...
Click to expand...

Actually, Cicero was saying that if (A) is illegal, then (not A) is legal, despite there being no written law to say so.
 
Dear 2Tizwoz

Thanks for the suggestion; I've already tried Metals Supermarket and their price for a 2 meter length is much the same as metals4u at about £300 including VAT.
 
There was a thread here about this subject and the opinion was that a solid wood post would be better than a steel tube.My Fulmar along with many others have this system and there were never any failiures.
 
macd said:
Your Latin teacher seemed to prefer mystifying his pupils to educating them. .
Click to expand...

You are correct about mystifying me, but I do remember some of it ie
Amo, Amas, Amat, Amamus, Amanti, Amant.
Not bad, I suppose, for 51 years since leaving school but I am b..gg..d if I know what to do with it

Sorry about the thread drift, but a bit of "learning" must do some good on this forum
 
vyv_cox said:
As David2452 says. Pipe has a fixed bore with variable wall thickness, normally according to internal pressure requirements. They are known as 'schedules' and Googling will give you the information you want. For stainless steel the schedules are more limited than for carbon steel and you may not be able to find exactly what you want.
Click to expand...

Not quite correct. Pipe has a fixed nominal bore which was based on heavy wall cast iron pipes in the victorian era.
In fact the Outside diameter of pipe is constant for different wall thicknesses. For example My tables give the following values for 3 inch(80 mm) pipe.

Nominal Bore 3 inch (DN 80 mm), Outside Diameter 88.9 mm(in all cases)
Schedule Sch. 5 Sch. 10 STD XS Sch. 160 XXS
Wall thickness (mm) 2.1 3.0 5.5 7.6 11.1 15.2
Internal Diameter (mm) 84.7 82.9 77.9 73.7 66.7 58.5

Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS.

Handily, the British standard pipe system (BSP)was adopted into the metric system "as is" so apart from converting the units, there is nothing new to learn.

Stainless tube on the other hand is quoted as OD and wall thickness. Here there is a difference between metric and imperial and certainly in this part of the world one can source imperial 2 inch SS tube (50.8 mm) or metric 50 mm tube.

A suggestion for the OP: I am appalled at the rip off prices you have been quoted - worth hunting for someone who will cut a length at reasonable cost.
Pipe does tend to be industrial mill finish rather than aesthetically pleasing such as polished tube. Why not use a piece of 2 1/2 inch (65mm)schedule 40 Galvanised pipe with a loose outer cover of 80 mm SS tube for the look of the thing. Below decks and protected like this I would think the galvanised pipe would last approximately forever!
Bet you wouldn't be able to bow that with rig tension!
Good luck.
 
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