Need to measure some cylindrical storage tanks for their diameter

[Daedalus685]

Oh, another good method which is often overlooked is to find the serial numbers and look it up!

You'd be shocked how many of these things are very standard and recorded for years. We have some LN2 tanks that must have been built in the 60s on site with clear spec sheets available online.

Edit: I lose this time.

 

[Howard]

Fill them full of water - take note of how many gallons. Once you've figured out the volume of water, a quick calculation will give you the diameter of the tank.

You realize that I said in my post that the tanks were between 8 and 14 feet in diameter, right? With height to match?

 

[Howard]

Ask the owner of said tanks?

Look at the purchase order for said tanks?

owner is us

Good idea. Now I wonder where we got them...

 

[AyashiKaibutsu]

barrel distortion

I was hoping that you guys could come up with something other than walking around with a string. The tanks are damn dirty and I can't get access to the full circumference for many of these tanks.

Edit: Err completely misread

 

[Howard]

don't need the volume, just the diameter

 

[AyashiKaibutsu]

don't need the volume, just the diameter

Yea, that was my bad. Maybe attach two poles to opposite ends of the tank and then run a string/measuring tape between those?

 

[highland145]

Any material handy that you can copy the shape of the arc. You would have the length of the "material" (arc length) and the segment length. Could figure the circumference from that.

 

[SKORPI0]

Circular segment

Measure S and C to get R. ^_^

 

[Kev]

Circular segment

Measure S and C to get R. ^_^

you win the thread!

 

[eLiu]

Circular segment

Measure S and C to get R. ^_^

FUUUUUUUUUUUUUUUUUUUUUUU

I came in here to post this. I hate you

 

[Howard]

How best to measure C? Form something around the circumference, take it off, and measure that?

 

[vshah]

How best to measure C? Form something around the circumference, take it off, and measure that?

string & tape method mentioned above for a decent distance should do it

 

[lxskllr]

How best to measure C? Form something around the circumference, take it off, and measure that?

Use a 2x4. That way you know what C is.

Edit:
You can't compute the tangent distance before you know what the radius is.

 

[Howard]

Use a 2x4. That way you know what C is.

What?

 

[lxskllr]

What?

Make a mark on the center of your tank. Offset the length of 2x4 from the tank. Check each end of the 2x4 to the mark you made using triangles. Then measure to the tank at right angles to the 2x4. The length of the 2x4=C, and you calculate the rest.

Edit:
By "center of tank" I mean your measurement point, not the radius point.

Edit2:
Not to scale or anything, but this should give you an idea. The end measurements to the tank need to be 90° to the 2x4. I forgot to draw that :^/

Edit3:
If you choose this route, don't use my actual numbers. I was being lazy, and didn't want to pull out a calc. The 2x4 would have to be 20' long to use my numbers :^S

 

[Leros]

Which one?

"Maths" = "Mathematics"

Maths is technically correct, except for our bastardized version of English.

 

[Rubycon]

ASME stamps should get you vital vessel information.

A laser can be used with a beam expander/adjustable collimator can find dimensions without even touching the tank too.

 

[Squisher]

How accurate do you have to be? Plus or minus an inch? Plus or minus a foot?

 

[jaha2000]

ASME stamps should get you vital vessel information.

A laser can be used with a beam expander/adjustable collimator can find dimensions without even touching the tank too.

Typically a storage take is not going to be an ASME rated tank. API650 is much more likely for a flat bottom storage tank.
At any rate, the nameplate should give you the information that you need to at least get in touch with the folks that made the tank. The name plate should not be insulated over..
If they were good, the nameplate will have the volume on it, measure the height of the tank and your done!

 

[SKORPI0]

Online calculator here :hmm:

Enter length of arc and width of arc to get radius. Like suggested earlier bring a 2x4, put it against 2 end points in the arc and measure length and
width. Of course bring a long measuring tape with you.

Picture with stick (2x4) to illustrate. As seen in picture stick is about 11.4 cm and arc about 14.3 cm, so radius is about 6.27 cm.
Diameter is approx. 12.5 cm.

 

[Howard]

Online calculator here :hmm:

Enter length of arc and width of arc to get radius. Like suggested earlier bring a 2x4, put it against 2 end points in the arc and measure length and
width. Of course bring a long measuring tape with you.

Picture with stick (2x4) to illustrate. As seen in picture stick is about 11.4 cm and arc about 14.3 cm, so radius is about 6.27 cm.
Diameter is approx. 12.5 cm.

Neither the tops nor the bottoms of the tanks are flat.

 

[jaha2000]

Neither the tops nor the bottoms of the tanks are flat.

Are they F&D or elliptical? If you had a way to measure the knuckle radius on the heads, i have a pressure vessel design book here and could tell you the diameters.

 

[BassBomb]

don't need the volume, just the diameter

Volume can be a good help to estimate the diameter, provided you know the height too

 

[Paperdoc]

Do you need outside or inside diameter? Inside is what's needed IF you need the holding capacity of the tanks.

Even if you could walk around them all, the string technique has two problems. One (you could probably manage this) is that the path of the string must remain in a horizontal plane (perpendicular to the axis if the cylinder). The other is that most string will stretch, and how much depends on how hard you pull. So you need a flexible material that will NOT stretch, like a light wire.

I think the best answer here is from Daedalus 685, although it may require use of a surveyor's transit to measure the angle accurately. Plus, of course, a longer measuring tape - at least 50 feet - and sufficient space to back up from each tank and still see it. And of course, most of these techniques still get us to the EXTERIOR diameter. BUT, bonus: if you have the equipment and math skills to measure diameter this way, you can also get the height at the same time.

 

[BassBomb]

Well if he can get the interior diameter it shouldn't be hard to find out the thickness of teh walls