How to measure diameter of pressure vessels?

[Curiousgeorge]

I would think that a tape measure will do, Just hold the hooked end stationary and move the tape around until you get the highest reading, then you know that you are across the ctr.

I’m learning all the time here! Thank you.

 

[Curiousgeorge]

Is the body laser cut, with holes in it by any chance?
Longitudinal seam welded and dressed out prior to putting on the ends?

All apart from the dressing - not sure what this is! Other than that - correct!
How did you know?

 

[Hitch]

If they're significantly sized cutouts, that will affect the rolling, small ones won't matter.

Dressing, once welded the seam probably has gone a bit out of shape. Knocking the seam back with a hammer and dolly will get it back to shape at the ends.

When the ends get tacked on, it's difficult to start out exactly right, if there just a few mm in difference between the circumference of the knuckle and the barrel, you'll have to start off with a slight step. Usually dress in to match once tacked up.

What thickness and diameter are we talking?
Small quantity, or a large number?

 

[Curiousgeorge]

If they're significantly sized cutouts, that will affect the rolling, small ones won't matter.

Dressing, once welded the seam probably has gone a bit out of shape. Knocking the seam back with a hammer and dolly will get it back to shape at the ends.

When the ends get tacked on, it's difficult to start out exactly right, if there just a few mm in difference between the circumference of the knuckle and the barrel, you'll have to start off with a slight step. Usually dress in to match once tacked up.

What thickness and diameter are we talking?
Small quantity, or a large number?

Thank you for all this.
1.2mm stainless steel and, off the top of my head, 18 inch diameter.
Quantity - every hour of every day
The only difference is length of cylinder.

 

[wyn]

Maybe it's not rolled properly and you still have a flat bit at the join.

 

[500e]

Start at the beginning of the process work your way through step by step that will give you a method of manufacturing then look at every step as a separate job.
Are the blanks the same & square, are the weld gaps the same, hand welded or machine are the finished tube the same diameter ? are the caps flat or dished are they the same diameter & does it match the finished tube.
Their are other steps but that should be a start.
You could make a simple rod & tube measure to give a rough check on the tube.
You are making enough for it to become a pain if the customer feel quality is not there.

 

[Curiousgeorge]

Start at the beginning of the process work your way through step by step that will give you a method of manufacturing then look at every step as a separate job.
Are the blanks the same & square, are the weld gaps the same, hand welded or machine are the finished tube the same diameter ? are the caps flat or dished are they the same diameter & does it match the finished tube.
Their are other steps but that should be a start.
You could make a simple rod & tube measure to give a rough check on the tube.
You are making enough for it to become a pain if the customer feel quality is not there.

You’ve pretty much said it all. Perfect.

 

[Screwdriver]

What you need is a wheelwrights travelers tool. A very simple yet incredibly accurate method for measuring internal and external circumferences. Not just measuring but also comparing relative sizes for fitting - which is what you're after.

I can post links to how they are used if you like.

 

[Turbo]

To me it sounds like you are having to botch the cylinders to make them fit the end caps. Hammering them into place & filling up the gaps with weld is not good engineering, especially on a pressure vessel! I'm surprised your company can get them certified as pressure vessels given the obvious lack of quality control!

If you saw a calor gas cylinder being manufactured in that way would you use it?

 

[Curiousgeorge]

To me it sounds like you are having to botch the cylinders to make them fit the end caps. Hammering them into place & filling up the gaps with weld is not good engineering, especially on a pressure vessel! I'm surprised your company can get them certified as pressure vessels given the obvious lack of quality control!

If you saw a calor gas cylinder being manufactured in that way would you use it?

I’m new to the place and they are a lovely bunch so won’t comment on what you said.....but I’m not arguing with you.

 

[8ob]

I may have the wrong end of the stick here , it sounds like the cylinders are cut to size and then rolled. With the best will in the world rollers wont make a perfect circle without scrapping the lead in/out material, at best you will be getting seven eighths of a circle and two flat bits.

Bob

 

[Curiousgeorge]

I may have the wrong end of the stick here , it sounds like the cylinders are cut to size and then rolled. With the best will in the world rollers wont make a perfect circle without scrapping the lead in/out material, at best you will be getting seven eighths of a circle and two flat bits.

Bob

Again, excellent points. My own opinion is that the post-rolling longitudinal seam welding probably doesn’t help either.

 

[chris pruteanu]

I make loads of alambics, heating manifolds and pots out of 1.2, 2mm and 3mm stainless steel sheet cold rolled by hand on a rolling machine, the rollers are out of shape in the middle and as such they pull the steel a bit out of shape and i have to roll them one way then pull them out and roll them the other way to get the roll as even as i can. The ends caps are hammered by hand and finished with a plastic fcing hammer on a wooden stump and as such its not always perfect. I do hammer thewelded cylinders back in shape on a thick gauge steel pipe stand but i also have to play with the ends to meet the shape of the cylinder. They are coming out pretty well and never had an issue ! I am on my laptop but i will upload a few pictures of the ones i made last month, i work with copper, steel and stainless steel...We often build boilers for wood stoves with recovery smoke/heat systems and every 2-3 years we may have to re-weld a few due to thermal stresses- often due to faulty relief valves and less due to welding fractures ! Just to stress that we do cut the sheets by hand with angle grinders and slitting discs- we have a 65 years old guy that really knows it all when talking about steel and problem solving ! Last week i have done a 3m long manifold on which i welded 20 something 1" threaded bungs and the darn thing got banana shaped. I had to pull the hydraulic press out of the workshop and straighten it back inch by inch ! Came out like new !

 

[chris pruteanu]

I don’t take that many pictures of the work I do, just don’t have much time !

 

[chris pruteanu]

I kept trying to upload the pictures...not all work...

 

[addjunkie]

A big pair of these or with out the fancy gauge would work.

 

[chris pruteanu]

View attachment 170559

A big pair of these or with out the fancy gauge would work.

Bit overkill methinks...however in an industrial production enviroment it should justify the expense...

 

[Munkul]

it's always a fight. It never will be THAT easy to achieve perfect fitup. It just takes time and a combination of best rolling and tacking practices, sometimes even might need to tack dogs and wedges in to pull things flush.

We have the same sort of fight with pipework - welders always complaining about some of the cheaper fittings (elbows, tees etc) being out of round and resulting in bad fitup that's outside the procedure spec. There's not a lot that you can do with smaller pipe or fittings though.
All we can do is make sure we buy high quality fittings and pipe sourced from Europe, and reject anything that's out of round, on the code jobs.

 

[rtcosic]

What you need is a wheelwrights travelers tool.

I knew exactly what I was looking for.

I spent a while Googling measuring wheel and variants and couldn't get past surveyor's wheels.

Now I know what to put into the search box!

Thanks

 

[zeppelin builder]

the diameters /circumference must be as near as poss .
you cant get rid of exess metal by bashing it in with a hammer it will pop out somewhere else around the joint , the circumference is the important bit the tube will be out of round and you may need to dog and wedge the pipe to suit the dome end ,
another use full tool would be a dearman pipe clamp ,its a duplex chain with screw clamps that can be moved around the chain to chase the pipe in and make it as round as possible .
you may have to live with a step equalised as much as you can around the joint