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thread bigger than the pipe it is made on !?

thread bigger than the pipe it is made on !?

thread bigger than the pipe it is made on !?

(OP)
For instance
NPS 1 inch (DN 25) having outside diameter 33.4 mm will have BSPP thread OD 33.25mm;
NPS 2 inch (DN 50) having outside diameter 60.33 mm will have BSPP thread OD 59.61mm;
and so on.
But how come that NPS 2 1/2 inch (DN 65) having outside diameter 73.03 mm could (allegedly) have BSPP thread OD 75.18 mm !?

RE: thread bigger than the pipe it is made on !?

Maybe the answer to this mystery lies in the definition of the word "Nominal"

prognosis: Lead or Lag

RE: thread bigger than the pipe it is made on !?

(OP)
To make it more clear I put it as the table.
DN OD BSPP
6 10.29 9.73
8 13.72 13.16
10 17.15 16.66
15 21.34 20.95
20 26.67 26.44
25 33.4 33.25
40 48.26 47.8
50 60.33 59.61
65 73.03 75.18 Why this size stands out from the pattern indeed contradicting "common sense", so to say?

RE: thread bigger than the pipe it is made on !?

(OP)
Why "mystery" just on this size - not before neither after it ? And how definition of the adjective "nominal" can desolve this mystery ?

RE: thread bigger than the pipe it is made on !?


nom·i·nal
[nom-uh-nl] adjective 1. being such in name only; so-called; putative: a nominal treaty; the nominal head of the country.

prognosis: Lead or Lag

RE: thread bigger than the pipe it is made on !?

A nominal 65 mm pipe is NOT 65 mm dia - inside, outside, or pipe thread (actual outside - (% thread engagement factor)x2) .

Nominal mm pipe sizes are based on arbitrary almost-metric equal "names" for actual ANSI/STD pipe diamters "translated" into near-metric equivilents "stated" diameters.
That is, a 100 mm "pipe" is really a 4 inch pipe, which isn't 4 inches diameter anyway.

RE: thread bigger than the pipe it is made on !?

(OP)
To put my qwestion an other way. Why on ALL sizes the OD of a pipe decreases slightly as the BSPP thread is made on it (in the form of fillings primarily) but only on THAT exactly "nominal" sise the pipe's OD increases mysteriously ?

RE: thread bigger than the pipe it is made on !?

There must be an error on the data you are looking at?
"That which cannot be, therefore is not" Simple!

prognosis: Lead or Lag

RE: thread bigger than the pipe it is made on !?

(OP)
The error must be creeping from one source to another as I have seen the numbers in many ones.
Anyway, Merry Christmas !

RE: thread bigger than the pipe it is made on !?

Found that the OD of dn65 pipe=76.1mm, maybe this explains it is in the same range.
Check british standard and DIN pipe OD's,
where did You get the 73.03mm?
Greetings

RE: thread bigger than the pipe it is made on !?

(OP)
Thank you, that one is credible. There are others, however less flagrant discrepencies in DN to actual mm conversions.

RE: thread bigger than the pipe it is made on !?

You looked at the ASTM range, not British Std.

RE: thread bigger than the pipe it is made on !?

By the memory there could be different solutions for one DN size, with one called preferred size. I don't know if this is the case or probably as mentioned by europipe matter of diff standards. It is not possible to manufacture such a thread size by cutting "smaller" pipe (OK there are some technologies which could apply plastic deformation to increase the size by I don't think is practical for threads). and the last but not least, engineering companies try to avoid such a size DN 65 since it is not wide spread (could be hard to find it).

RE: thread bigger than the pipe it is made on !?

Pavel, like to concur with You, plastics came a long time after BSP thread and dn65 and 2.5" are still everywhere used especially in firewater- and foam systems.
We like to avoid it in new processlines-situations, but there are still many pumps and other equipment with
2.5" connections.
Here the table with difference in BS and USA pipe

http://www.marylandmetrics.com/tech/pipecomp.htm

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