Pipe Dims in AutoCAD 3 Views

[Sengna]

Does Anybody know that accurate rule when drawing the pipe dimension in Autocad? Should i draw the actual outside dimension O.D or do i have to go by the standard pipe size table? Example on the pic below, the O.D size is 1.66 in but when i look on the stadard table, it's 1-1/4 in, which dimension should i draw on CAD?

Thanks

 

[rkent]

Always use nominal pipe sizes, 1", 1-1/2", 2", etc.

[Sengna]

Always use nominal pipe sizes, 1", 1-1/2", 2", etc.

Will this apply to lumber dimensions as well when drawing in Auto Cad?

[ReMark]

We always draw the actual O.D. I work for a chemical manufacturing plant and pipe sizes typically run from 1/4" up to 8" with a handful of larger sizes for steam lines and cooling water (10-12" range).

 

When you draw your pipe handrails do you use the pipe O.D. or the nominal size?

 

When you draw the nozzles on a storage tank, reactor, condenser or a receiver do you use the pipe O.D. or the nominal size?

[ReMark]

Will this apply to lumber dimensions as well when drawing in Auto Cad?

 

I use the dressed size not the nominal size so a 2x4 gets drawn as a 1.5x3.5. What do you do?

[Organic]

Always use nominal pipe sizes, 1", 1-1/2", 2", etc.

 

This. Use the nominal internal diameter of the pipe. E.g. write 525mm (internal nominal diameter), not 600mm (roughly the outside diameter of the pipe). Hydraulically, fluid can only flow within the 525mm diameter of section the pipe, not the 600mm total diameter (including the thickness of the walls).

 

If you are checking clearances between services then it is necessary to use the outside diameter dimensions of the pipes. In general though all pipe sizes given on plans would be nominal sizes (you should have a note saying this though).

 

This is with regards to civil engineering. It may vary in other industries.

[ReMark]

I checked two fabrication drawings one by Roben for a 8,000 gallon storage tank, and one by Pfaudler for a 2.5 sq. ft. rototherm, and both manufacturers drew nozzles and piping using the O.D. of the pipe. Then I checked a drawing by a company called Globe (a division of United States Gypsum) for a set of stairs and landing they did for one of our reactor mezzanines and they too used pipe O.D. So, yes, maybe it does depend on the industry.

 

Senga: What field do you work in?

[RobDraw]

The type of drawing will affect how you draw it. From my experience, if you are drawing construction drawings to show placement and clearances and verifying that the pipe and fittings will fit, then the O.D. is used. System/schematic drawings will often have the N.D. or use single line representation because they are conveying the design of the system.

[ReMark]

My answer was based on the book "Process Piping Drafting" by Rip Weaver. I had the pleasure of attending one of his lectures at the Institute for the Certification of Engineering Technicians (New Jersey) many years ago.

 

Rip Weaver has over 25 years of experience in piping drafting, design and engineering. In his 17 years with Fluor Engineers and Constructors, Inc., he has worked on or supervised piping design for major refineries.

[rkent]

I have worked for various industries and Engineering firms and they all used nominal pipe sizes. Maybe a hold over from the board drafting days when you used plastic templates for elbows, valves, etc. because those were made to nominal pipe sizes. If not showing the thickness of pipe on a piping drawing causes interference out in the field then you aren't doing it right.

[ReMark]

Have you checked some of the fitting and valve block libraries available for AutoCAD? All the ones I've come across use O.D.

 

I'm not about to argue with the guy that practically wrote the book on piping drafting (Rip Weaver) nor one of the largest tank manufacturing companies in the world (Pfaudler). If O.D. is what they use it's good enough for me too.

[RobDraw]

I have worked for various industries and Engineering firms and they all used nominal pipe sizes. Maybe a hold over from the board drafting days when you used plastic templates for elbows, valves, etc. because those were made to nominal pipe sizes. If not showing the thickness of pipe on a piping drawing causes interference out in the field then you aren't doing it right.

 

...or you have a very tight space to work in. I agree that allowances should be made but not all CAD jockeys are aware of this.

[rkent]

It is easy enough to draw to true size with computers and with piping programs and library's for everything, now there is no need to draw the pipes and elbows anymore. I am just getting old. Multiplying 6 X 1.5 is easier than 6.625 X 1.5 . Or offsetting half of 6 VS 6.625, etc.

[ReMark]

You wouldn't believe how tight they run piping around here. In some cases you can barely slip a piece of paper between two crossing pipes. If this facility were built today we would easily need 50% more space to do things right.

[ReMark]

"I am just getting old."

 

You aren't getting to retire already are you?

[Sengna]

I checked two fabrication drawings one by Roben for a 8,000 gallon storage tank, and one by Pfaudler for a 2.5 sq. ft. rototherm, and both manufacturers drew nozzles and piping using the O.D. of the pipe. Then I checked a drawing by a company called Globe (a division of United States Gypsum) for a set of stairs and landing they did for one of our reactor mezzanines and they too used pipe O.D. So, yes, maybe it does depend on the industry.

 

Senga: What field do you work in?

I am working food processing plant, i am dealing with Mechinal equipment.

[Sengna]

We always draw the actual O.D. I work for a chemical manufacturing plant and pipe sizes typically run from 1/4" up to 8" with a handful of larger sizes for steam lines and cooling water (10-12" range).

 

Wow, many input, Sorry for late reply, i am on Pacific time

 

 

When you draw your pipe handrails do you use the pipe O.D. or the nominal size?

 

In the past, i have been drawing the pipe or pipe handrails, i use the standard size or nominal size. But yesterday i went to verify the pipe diameter with the caliper measure, it's dia is 1.66 in so I always not sure about what is the accurate way of drawing the pipe? Base on what i do, by drawing the object in the true size will help during installation. It avoids problem when i draw in true dims.

 

When you draw the nozzles on a storage tank, reactor, condenser or a receiver do you use the pipe O.D. or the nominal size?

I have not done much for these, i drew soem tanks in the past and i use true size.

[Sengna]

We always draw the actual O.D. I work for a chemical manufacturing plant and pipe sizes typically run from 1/4" up to 8" with a handful of larger sizes for steam lines and cooling water (10-12" range).

 

When you draw your pipe handrails do you use the pipe O.D. or the nominal size?

 

When you draw the nozzles on a storage tank, reactor, condenser or a receiver do you use the pipe O.D. or the nominal size?

What is O.D of 8" Pipe? Which Schedule that you use?

[ReMark]

8.625 for Schedule 40 pipe.

[rkent]

"I am just getting old."

 

You aren't getting to retire already are you?

 

I have at least ~6.5 more years to go and then if the SS I (and my employers) have paid into for 48 years is still there then I will retire.