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A Couple of Questions about Pipe?

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Swarf, Mostly!17/09/2021 19:41:14
646 forum posts
70 photos

I understand that gas pipe is colloquially referred-to as 'barrel' because the original town gas networks re-used the barrels from Government-surplus musket barrels from the Napoleonic Wars. (Or is this an urban myth? )

So, question #1: is it improper to also refer to water pipe as 'barrel' ?

Question #2: is galvanised water pipe galvanised on its interior as well as its exterior?

Engineering history can be obscure but interesting. For instance, why is the outside diameter of nominal 1½" pipe actually 1 and 29/32 inches?

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 17/09/2021 19:42:57

Dave S17/09/2021 19:47:02
363 forum posts
90 photos
Posted by Swarf, Mostly! on 17/09/2021 19:41:14:

Engineering history can be obscure but interesting. For instance, why is the outside diameter of nominal 1½" pipe actually 1 and 29/32 inches?

I think this one is because pipe sizes are measured for the bore.

Makes sense if you need to know how much stuff will flow down a pipe I think


DC31k17/09/2021 19:54:03
662 forum posts
2 photos
Posted by Swarf, Mostly! on 17/09/2021 19:41:14:

Question #2: is galvanised water pipe galvanised on its interior as well as its exterior?

If you know of a safe way to hot dip galvanise only the exterior, run down to the Patent Office and register the idea.

Steviegtr17/09/2021 22:56:59
2422 forum posts
336 photos

From memory of purchasing , the only barrel word I used was for barrel nipples. Thread each end .


Paul Lousick17/09/2021 23:42:32
2018 forum posts
712 photos

I am in Australia and never heard of pipe being referred to as barrel. The pieces of old water pipe that I have are galvanized on the inside as well as the outside. Otherwise they would rust.

Pipe is sized by its bore and as mentioned, originally used for calculating the flow of liquid thru it. The outside of pipes are a constant diameter to allow pipes with different wall thicknesses to screw into a common threaded hole (tees, elbows, valves, etc) Therefore the designation of a nominal bore size, not an exact bore size. Thicker walled pipes are required for higher pressures. Pipe is sized by its nominal bore and a schedule that specifies its wall thickness. Schedule 40 is the size used for common water pipe for homes.

Tube is specified by its OD and wall thickness (gauge size).


Edited By Paul Lousick on 17/09/2021 23:45:44

Martin Connelly18/09/2021 08:52:22
2125 forum posts
222 photos

British Standard Pipe (BSP) has a standard wall thickness, it is the size where the bore most closely matches the nominal size. It also came in lightweight. Both schedule 40 pipe and standard pipe were generally the minimum wall thicknesses to use for threaded pipes. Lower wall thicknesses were used to save weight and cost when they could be welded. For some ANSI standards (eg ANSI B36.10) schedule 40 is sometimes referred to as standard and sometimes the equivalent of schedule 80 is X Strong, there is also XX Strong. Pipe is designated as NPS or NB which are nominal pipe size and nominal bore which lets you know what to expect to some extent but you need tables to know exactly what you are going to get with any of these pipe designations.

The term barrel nipple only seems to apply to a nipple with an unthreaded centre section with a tapered thread either side, the result being a barrel shape to the side view. When there is no unthreaded centre section what you have is called a close taper nipple, you also get parallel nipples.

Martin C

Nicholas Farr18/09/2021 09:15:28
3329 forum posts
1531 photos

Hi, I agree with Martin with regards to barrel nipples. All the galvanized pipe that I've ever seen has been galvanized both inside and outside (That is when it is new)

Anyone remember running joints in pipework?

Regards Nick.

Edited By Nicholas Farr on 18/09/2021 09:19:45

Jim Nic18/09/2021 11:58:32
378 forum posts
214 photos

A little ampification on the nature of pipes:

1) Pipe is made of a long hole surrounded by metal or plastic centred around the hole.
2) All pipe is to be hollow throughout the entire length.
3) The ID (Inside Diameter) of pipe must not exceed the OD (Outside Diameter) -- otherwise the hole will be on the outside.
4) Pipe is to be supplied with nothing in the hole, so that water, steam or other stuff can be put inside at a later date.
5) Pipe is normally supplied without rust; this can be applied at the job site. NOTE: Some vendors are now able to supply rusty pipes. If available in your area, this product is recommended, as it will save a great deal of time at the job site.
6) All pipe over 500 ft (150 m) in length should have the words "LONG PIPE" clearly painted on each side and end, so that the contractor knows it's a long pipe.
7) Pipe over 3 miles (3.3 km) in length must also have the words "LONG PIPE" painted in the middle, so the contractor will not have to walk the entire length of the pipe to determine whether or not it is a long pipe or a short pipe.
8) All pipe over 6 ft (1.83 m) in diameter must have the words "LARGE PIPE" painted on it, so the contractor will not mistake it for small pipe.
9) Flanges can be used for joining pipe. Flanges must have holes for bolts, quite separate from the big hole in the middle.
10) When ordering 90 or 30 degree elbows, be sure to specify left-hand or right-hand, otherwise you will end up going the wrong way.
11) Be sure to specify to your vendor whether you want level, uphill or downhill pipe. If you use downhill pipes for going uphill, the contents will flow the wrong way.
12) Couplings should have either right-hand or left-hand threads, but do not confuse the threads otherwise, as the coupling is being screwed on one pipe, it can unscrew from the other.
13) Pipes shorter than 1/8 in (3 mm) are very uneconomical in use, requiring many joints. They are sometimes known as washers.
14) Joints in pipes for pumping compressed air must be air-tight. Those joints in pipes for water, however, need only be water-tight.

wink 2


larry phelan 118/09/2021 18:44:52
1172 forum posts
15 photos

Makes more sense than many other posts !

JA18/09/2021 19:35:48
1346 forum posts
80 photos

Jim is right.

Once you have a hole you can do anything with a pipe, or tube. You can make it smaller, larger and even turn it in side out (if the material allows you to do so). The latter was a party trick at the BSC Corby research labs.

A couple of comments: Pipe, tube, can be made from welded strip (seamed) or bar that has had a crack induced up its centre (seemless). The high pressure boiler tube we produced was actually made from strip (it was beautful stuff). Seemed tube has a very consistent wall thickness but the control on diameter can be poor. The converse is true for seemless tube.


Russell Eberhardt18/09/2021 19:53:11
2728 forum posts
86 photos

Just be careful how you ask for pipe in France! devil


Chris Gunn18/09/2021 19:55:13
429 forum posts
27 photos

JA, just seen your reference to working at Corby, did you work in the DR&TD? if so which department? did you know anyone in the Control Systems section?

Chris Gunn, DR&TD, 1969-73.

V8Eng18/09/2021 20:22:14
1697 forum posts
1 photos
Posted by Russell Eberhardt on 18/09/2021 19:53:11:

Just be careful how you ask for pipe in France! devil


Ha Ha yes.😊

JA19/09/2021 16:45:20
1346 forum posts
80 photos


I have sent you a PM.


Meunier19/09/2021 19:51:29
448 forum posts
8 photos
Posted by V8Eng on 18/09/2021 20:22:14:
Posted by Russell Eberhardt on 18/09/2021 19:53:11:

Just be careful how you ask for pipe in France! devil


Ha Ha yes.😊

Not so much as a peep from me.

Peter Ellis 519/09/2021 22:34:58
101 forum posts
11 photos

I was intrigued to discover that, in otherwise all metric Croatia, when I wanted pipe to make up pipe clamps, I had no difficulty, as it was all clearly marked 1/2 ¨ 3/4¨, etc. None of it was metric.


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