Why does black iron pipe and galvanized come in 21 foot lengths instead of 20 and 10 foot lengths like most other pipe materials? I was thinking that it may have something to do with pipe manufacturing methods from long ago that maybe they just haven't changed. If anyone knows of a practical reason for this odd measurement let me know

Good trivia question ! It reminds me question I've heard few years back: Why are rail road tracks 56.5" wide ? :confused:

I tried to do some research - but got no viable explanation yet. Nobody seems to know. One rep told me 21' is the length of average flat bed track / cargo area. The other one told me that the 21' derives from foreign manufacturers who measure in meters. To them, it is 7 meters long. Little vague... but at least something to start with...

Obviously, there must be a reason for cutting it at this length: during manufacturing, pipes are pulled hundreds of feet at the time and then cut to 21'... I will keep asking and let you know when I get better answer...

The other one told me that the 21' derives from foreign manufacturers who measure in meters. To them, it is 7 meters long. Can't buy that one, 7 meters= 23.1ft. 6 meters= 19.8 No 21feet there. I'm looking also and can't come up with anything on the web. We'll keep on looking! Regards, Tom

Can't buy that one, 7 meters= 23.1ft. 6 meters= 19.8 No 21feet there. I'm looking also and can't come up with anything on the web. We'll keep on looking! Regards, Tom

Good point Tom... Let me know what you find out !

Still checking milo. No joy yet! Tom

[QUOTE=;][/QUOTThe 21' length became the standard because of the old way pipe was produced. Pipe was produced in the past using the bell and tongue method. This method of pipe making started with a heated ( red hot - close to melting temperature) length of steel strip and then the strip was manually pulled with a pair of tongues through a bell. Hence the bell and tongue method. The bell was used as both the forming roll and the welding roll. The 21 foot length was the length that could be produced and still keep enough heat in the strip to produce a good weld. A longer length would not have produced suitable weld quality over the entire length. Shorter pipe would not have as good a yield.
Hope this helps.E]

[QUOTE=;][/QUOTThe 21' length became the standard because of the old way pipe was produced. Pipe was produced in the past using the bell and tongue method. This method of pipe making started with a heated ( red hot - close to melting temperature) length of steel strip and then the strip was manually pulled with a pair of tongues through a bell. Hence the bell and tongue method. The bell was used as both the forming roll and the welding roll. The 21 foot length was the length that could be produced and still keep enough heat in the strip to produce a good weld. A longer length would not have produced suitable weld quality over the entire length. Shorter pipe would not have as good a yield.
Hope this helps.E]

Thanks for the post. But it is kind of vague about the length...

[QUOTE=parttime;1337948]

Thanks for the post. But it is kinda vague about the length.....

Vague about the length? Or are you dense?

We got it! Thanks Partime for the explanation. Tom

[QUOTE=Milo Dolezal;1337963]

vague about the length? or are you dense?

Of course, now when I read it for the second time, I see it explained. Good job ! :D

The bell, and tonge explanation sounds plausible, but I'm a little skeptical.
FYI, "standard gage" railroad track originated in Britain, and was based on the ruts left by roman chariot wheels.

Hi alilrusty,
Exactly what troubles you about the bell, and tonge explanation and what do railroad tracks have to do with pipe lengths? Back to you, Tom