A question:

I am looking at a Hancock Locomotive Specialties Bulletin No. 301, 1928. It covers the Hancock Inspirator type A. I notice that in the table of pipe connections, broken down by size of inspirator, an odd detail. For example, a size #10 inspirator requires a steam and delivery pipe in 2” iron pipe or 2-1/4” copper pipe. The suction for the same inspirator is listed as 2-1/2” iron pipe or 2-3/4” copper pipe. And again, for the overflow, 1-1/2” iron pipe or 1-3/4” copper pipe.

The text is very explicit in that the copper is pipe not tube. IPS (iron pipe size) and CPS (copper pipe size) today are the same dimensions inside and out regardless of being schedule 40 or schedule 80.

Hancock will supply the nipples or tail pieces to suit your choice in pipe, be it iron or copper.

I have never seen iron or copper pipe in 2-1/4”, 2-3/4”, or 1-3/4” for American pipe.

I do know that British standard pipe, one hundred years ago, was available in ¼” increments up to 4” pipe and that in the sizes that corresponded to American pipe the diameters were close.

I don’t find evidence that Hancock was involved in European business.

So, the question: Why the two sizes of pipe for the same connection dependent on material?

Was copper pipe and iron pipe sized differently one hundred years ago? Did the copper pipe have a thicker wall to hold the pressure, copper being a weaker material?

Inquiring minds want to know.

Well, this gets confusing fast...

"Pipe" and "Tube" dimensions are a big tangled up mess even on just one side of the Atlantic Ocean...

Iron pipe is the simplest, with nominal OD's that are the same for all schedules (40, 80, X, XX) so the threads are the same to fit the fittings. The ID gets smaller as the "schedule" (aka strength) goes up.

I disagree, see my prior paragraph.

Pipes made of brass, stainless steel and other "exotic" metals generally follow those same rules (nominal OD, ID determined by the schedule)

Copper "pipe" like the rigid "sticks" of pipe you find at your local big box DIY store follows the same principle, the nominal OD is fixed to match the fittings and the ID goes down as the strength goes up. There are several Copper "pipe" schedules; K, L, M, DWV, Medical Gases...

https://www.copper.org/applications/plu ... _type.html
Click on the Table 14.1 link

Funny thing is the people that manufacture copper "pipe" call all of these grades "copper tubing"...

Other folks have called any rigid piece of copper "tubing" "copper pipe"... But you can buy all of those Copper "pipe" sizes you find at the local DIY store as rigid "sticks" as annealed rolls of exactly the same size.... And you can unroll them to make straight lines of copper "tubing" that looks awfully like a "pipe"....

Then there are the small sizes of "tubing" like the rolls you might use to hook up the ice maker in your refrigerator... Those actually have an OD that matches the "nominal dimension", IE 1/4 tubing has an OD of 0.25"...

And then just to throw another twist into the question the HVAC industry has a whole different set of tubing sizes.... The HVAC industry in the USA started with different sizes and they have stuck with them... So a 1/2" copper refrigerant tube on your HVAC will not fit a 1/2" copper water pipe....

So I would wager that the original specs for the device you are interested in specified a larger copper "pipe" size knowing that a higher strength "pipe" would be needed and that would have a thicker wall. Thus the ID of the copper "pipe" would be about the same as the ID of an Iron pipe with the same strength....

Some folks using that device would use rigid iron pipe with elbows, unions, etc to connect it up. Iron Pipe is pretty darn tough. Others might use an annealed copper "pipe" so they could easily "bend" it around obstacles to go where it needed to go. Kinda of an "end user" preference.

And that's just in the USA... Makes my head hurt just trying to explain it...

Cheers, Kevin

Here's an example of pipe "sizes" for "iron pipe";

https://www.magellanmetals.com/pipe-chart#twos

This shows "nominal" 1/2" pipe with schedules from 5, 10, 40/STD, 80/XS, 160 and XX.

In all cases the nominal OD is 0.840", but the ID ranges from 0.710" (schedule 5) to 0.252" (schedule XX).

This is just what the "historical iron" pipe manufactures decided to use, the Copper "pipe" folks set their own standard; K, L, M, DWV, etc. DWV is Drain/Waste/Vent pipe used to connect your crapper to the sewer and is very low pressure (a few 10's of PSI) since it is all forced by gravity and is not really a "pressurized" system.

Well, at least until the unfortunate person with a sensitive stomach has a garbage plate..

I was soooo... tempted to "go there" but decided to keep my reply "Sanitary..."

Cheers, Kevin

Most of the discussion above is about tubing, the original poster ask about copper pipe. Copper pipe is made to specification ASTM B-42. In looking at this specification and comparing it to the steel pipe sizes shown in the Machinery’s Handbook, the copper pipe has a thicker wall thicknesses than steel pipe has for the same nominal size and schedule.

The Western Railway Museum has purchased copper pipe in the past. Some drum controller segments are the same size as some of the schedule 40 copper pipe. The pipe can be parted off into rings and then cut into segments. This avoids the problem most home made segments have of flattening out at the ends. I assume this works because the original General Electric drum controllers used copper pipe for segments. Copper pipe is 99.96% copper, which makes it a good electrical conductor.

When looking for copper pipe, I think the size needed was 3 1/2” nominal diameter, the copper supplier I talked to told me that the only use he knew for copper pipe was as buss bars in power company substations. I was able to buy a 3’ length.

.

Thank you all for your descriptions of pipe and tube. I am aware of the differences however and not interested in a remedial lecture.

If anyone has any insight into the initial question of why manufacturers specify different sized connections based on material I would be most interested in hearing it.

David Johnson has already answered this. I quote:

"Most of the discussion above is about tubing, the original poster ask about copper pipe. Copper pipe is made to specification ASTM B-42. In looking at this specification and comparing it to the steel pipe sizes shown in the Machinery’s Handbook, the copper pipe has a thicker wall thicknesses than steel pipe has for the same nominal size and schedule."

Lower strength means thicker wall. Thicker wall means smaller hole. Smaller hole means less flow... So if you want equal flow, you need to specify larger copper pipe.

Fair enough, but if you don't want a remedial lecture then you should have known that the material (Iron, Steel, SS, Brass, Monel, Copper, Plastic, Glass) that a pipe/tube is made from defines it's strength (ie maximum working pressure).

At any given maximum pressure a pipe/tube made of a "less strong" material like copper versus iron requires a thicker wall. To maintain the same flow the ID needs to be constant, thus the OD increases to make the system work. QED

You say Pipe, I say Tube....

As the terms are generally accepted;

A pipe is fairly rigid and can be threaded but not easily bent...

And;

A tube is fairly flexible and can be bent but not easily threaded...

BUT of course there are exceptions to the "rules", iron pipe is routinely bent with some extra effort. And there are some low pressure applications where tube is threaded with some extra effort. I have seen old pneumatic control systems that had threaded connections on the ends of aluminum "tube" that was threaded and connected with fittings. And the plumbing trades routinely call rigid sticks of copper water "tube" pipe....

Cheers, Kevin.

I wonder how long the ASTM B-42 std on copper pipe has been around?
Inquiring minds want to know.

I'll reach reach out to my ASTM connections at ASTM HQ in the center of the universe,
West Conshohocken, PA. (sorry Kelly)

C W

The web page https://www.astm.org/Standards/B42.htm has a link for "historical versions". I interpret that info to imply that the oldest version of B-42 available there is from 1993.

Bob Milhaupt

Thanks Bob,
The Historical versions only go back thru the electronic versions which started back in the 90's with CD's or print versions of the volumes.
Prior paper versions may be available or not from ASTM.

C W

I should say the historical versions "on the website" only go back as far as the availability of the electronic (PDF) versions.

mid 90's as I recall, after 25+ years on an ASTM committee I can't remember those details any more. I would have to look hard (wearing glasses now) at my notes to find out for sure.

The 93 version of the copper pipe std. was the current version on file when ASTM started offering electronic (PDF) versions. So sometime between 93 and 99 they started offering PDF's (7 years for a version to sunset or get revised 5 + 2 grace years).

On another note, this may be the last year "paper" volumes of standards will be available from ASTM.
Going all electronic.

C W

C W

I would look in an old Machinery's Handbook. Old versions are available online...in pdf form.
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