Convert square footage to linear footage of pipe formula??

[Marq]

I am getting confused on something, and I know its simple but I can't wrap my head around it.

I am making a bill of materials for insulation that goes around pipe. In two layers.

So for example I have a 350 lnft long 10" pipe which requires two layer of 10mm insulation. The software I have which spits out my BOM based on lnft can only provided the answer is sqft, which the software says I need 2,310 sqft of the insulation material to meet the 2 layers of 10mm for the 350 long 10" pipe.

But when I calculate the sqft manually I get a different answer:

1st layer 10.75" circumference .895 x Pi = 2.812 x 350lnft of pipe = 984.52

second layer 11.15" circumference .929 x Pi = 2.91 x 350 lnft of pipe = 1,021.156


MY TOTAL: 2,005.67
Software total : 2,310

So what would be the fomula to convert that 2,310 sqft to linear footage of 10" pipe??? I want to reverse engineer see what the linear footage is of the 2,310...if i manually do it its around 821 lnft.....(by manually i just keep increasing my lnft in my sqft formula till i get to 2310 sqft..(10.75" circumference = .895 x P1 = 2.812 x 821lnft = 2,310.58)

350 lnft of inner layer and 350 ft for outer layer = 700 lnft of insulation needed.....but based on the software sqft, it says I need 821 lnft of insulation. There is no waste factored in on the software, so the software sqft should equal 700 lnft of insulation needed...not 821.


for some reason i cant figure out the reverse engineer formula to convert the sqft of pipe to lnft of pipe.

 

[6StringJazzer]

What are the inputs to your software? Is it making the same assumptions you are about the effective circumference of the two layers of pipe to cover? I am guessing the discrepancy is in the circumference rather than the pipe length.

If the software uses the same diameters as you, then it is using 402.9 linear feet.

I did not do the calculation of diameters assuming linear feet is 350; that is complicated by the fact that you have two diameters, and I have no idea what your software is or how it works.

The formula to get linear feet working backwards from the other parameters is shown in this file.

Dropbox - File Deleted - Simplify your life

www.dropbox.com

 

[Marq]

What are the inputs to your software? Is it making the same assumptions you are about the effective circumference of the two layers of pipe to cover? I am guessing the discrepancy is in the circumference rather than the pipe length.

If the software uses the same diameters as you, then it is using 402.9 linear feet.

I did not do the calculation of diameters assuming linear feet is 350; that is complicated by the fact that you have two diameters, and I have no idea what your software is or how it works.

The formula to get linear feet working backwards from the other parameters is shown in this file.

Dropbox - File Deleted - Simplify your life

www.dropbox.com

I put in the software 10 inches and 350 lnft...2 layers (each insulation thickness is .20 inches)..it is an inhouse software which i do not have access to the formals...I just plug in my lnft, pipe size and how many layers.

 

[Marq]

What are the inputs to your software? Is it making the same assumptions you are about the effective circumference of the two layers of pipe to cover? I am guessing the discrepancy is in the circumference rather than the pipe length.

If the software uses the same diameters as you, then it is using 402.9 linear feet.

I did not do the calculation of diameters assuming linear feet is 350; that is complicated by the fact that you have two diameters, and I have no idea what your software is or how it works.

The formula to get linear feet working backwards from the other parameters is shown in this file.

Dropbox - File Deleted - Simplify your life

www.dropbox.com

i can not open the excel workbook you posted....i cant open dropbox on my work pc

 

[6StringJazzer]

I can think of no other way to make it available to you.
Data Range

	A​	B​	C​	D​	E​
1​	Working forwards​	​	​	​	​
2​	Diam (in)​	Circum (in)​	Circum (ft)​	Lin ft​	Sq Ft​
3​	10.75​	33.77​	2.814​	350​	985.02​
4​	11.15​	35.03​	2.919​	350​	1,021.67​
5​	Total​	​	​	​	2,006.69​
6​	​	​	​	​	​
7​	Working backwards from diameter​	​	​	​	​
8​	Diam (in)​	Circum (in)​	Circum (ft)​	Lin ft​	Sq Ft​
9​	10.75​	33.77​	2.814​	402.90​	1,133.90​
10​	11.15​	35.03​	2.919​	402.90​	1,176.10​
11​	Software total​	​	​	​	2,310​

E9: =E3/$E$5*$E$11
D9: =E9/C9

 

[6StringJazzer]

(each insulation thickness is .20 inches)

You originally said the thickness was 10mm, which is about 0.4 inches. That is consistent with the diameters you used. Is the above number an error?

 

[jasonb75]

A couple of thoughts.

Is it possible that the inhouse software assumes a 10 inch bore and allows for the wall thickness of the pipe?

Bearing in mind that when you roll the flat insulation around the pipe, the circumference of the outer face of the insulation will be greater than that of the inner face. From the information you provided it appears that you have already factored this in, but If your measurements are based on a different point to thos used by the software then that would allow for at least some of the difference.

 

[glfiedler]

I would think you would need to calculate square footage based on the outside of the insulation. That would mean the first layer's OD would be the 10.75 pipe dia plus the 0.4 in insulation. So your first diameter would be 11.15 inches or 0.9286 feet. The second layer would than be 15.15" or 1.26 feet. See if those diameters are closer to your software results.

 

[glfiedler]

Using my diameters for the outside face of the insulation per previous post I calculate 2406.49 square feet for 350 feet of pipe.

 

[glfiedler]

Please ignore my calculations. It is way too late in the day. I did not take the full thickness into my numbers. But I still think you should use the outside face of the insulation.