ShareThis

Saturday 20 April 2013

Understanding pipe diameters




There is often confusion amongst new users of industrial plastic pipe as to the actual measurements of the internal bore and external diameter. Over the decades, and indeed centuries, there have been many adapted and modified standards, some of which have been long abandoned, but others which have remnants in today’s specifications.
To understand how plastic pipe is measured, the user must first understand the methods of production and consider the way that industrial plastic pipes are generally assembled:
The machines that manufacture lengths of plastic pipe heat plastic pellets and then squeeze them through a die. This allows the wall thickness and diameter to be controlled. The problem comes in the cooling process, where, like all materials, the hot plastic contracts. If this were left unchecked, the finished product would have a varying external diameter and bore, which would result in a poor fitting product that is next to useless. The pipe manufacturers concentrate on maintaining a fixed external diameter, and let all the shrinkage happen to the internal diameter / bore of the pipe. It is here that we need to appreciate how industrial plastic pipe is assembled. In general, and this is true for both solvent weld pipework such as pvc pipe and electrofusion welded materials such as polypropylene, assembly is by inserting a pipe into a socket. The external diameter of the pipe is therefore critical, as any variation will make a poor joint with the socket. The internal diameter is less critical as it does not have to perfectly match anything else.
The plastic pipe manufacturers therefore control the outside diameter of the pipe. The external diameter of the pipe therefore remains constant, and the internal diameter varies depending on the pressure rating (due to a thicker wall). It is important to note that even with the same manufacturer, wall thicknesses for the same specification of pipe can vary slightly, resulting in a slight bore variation (usually less than 0.5mm). This is certainly the case between different manufacturers and the internal bore should not be relied on for machining purposes.
With metric pipe, and this knowledge, determining the pipe dimensions is simple; te outside diameter of the pipe measures the same as the stated size; so a 50mm pipe has a 50mm outside diameter, a 90mm pipe a 90mm outside diameter etc. Unfortunately the same cannot be said for imperial (inch) pipe. This is an area of great confusion as the size of the pipe refers to the “nominal bore” (or to put it another way “approximate bore”) of the pipe. So, a 2 inch pipe has an approximate bore of 2”. As the outside diameter of the pipe needs to remain fixed, to allow for fitting into sockets etc. the wall thickness of the plastic pipe changes with pressure rating and so, as a result, does the bore…which is why it is referred to as “nominal”. So a 2” pipe does not actually measure 2” anywhere! Many inexpereicnced users will order a 2 inch pipe and expect it to have an outside diameter of 50.8mm but in fact the OD is 60.3mm.
The general rules of thumb are:
Metric pipe – will measure the stated diameter as an external diameter
Imperial pipe – Will not measure the stated diameter anywhere so the user must check first in the table below:
Pipe size (inches)
Outside diameter (mm)
3/8
17.1
½
21.4
¾
26.7
1
33.6
1 1/4
42.2
1 1/2
48.3
2
60.3
2 ½
75.2 (Note that for North American Pipe 2 ½” = 73mm)
3
88.9
4
114.3
5
140.2
6
168.3
8
219.1
10
273.0
12
323.9

10 comments:

Master Pipe said...

Very well said. this post is really amazing. I appreciate it for sharing them.

Plumbing Pipe
Pvc tube

PipeFittings said...

this post is really amazing. Stainless Steel Pipe Fittings

Anne said...

Great writing. Thanks

Master Pipe said...

Helpful tips everyone should surely follow i would also like to add a few points for sewer cleaning
1)Have a plunger near you
2)Keep the drain clean
3)Manage your use of water


Plumbing Pipes

Unknown said...
This comment has been removed by the author.
Unknown said...

This is just the information I am finding everywhere. Thanks for your blog, I just subscribe your blog. This is a nice blog.. stainless steel pipe fittings

Naveed Mughal said...

Thanks for sharing the post.. parents are worlds best person in each lives of individual..they need or must succeed to sustain needs of the family.
fittings manufacturer

Online Tips said...

Pretty good post. I just stumbled upon your blog and wanted to say that I have really enjoyed reading your blog posts.
http://www.valvefittingstore.com/

Lea Paige Matteo said...

How Lemeridian funding service  grant me a loan!!!

Hello everyone, I'm Lea Paige Matteo from Zurich Switzerland and want to use this medium to express gratitude to lemeridian funding service for fulfilling his promise by granting me a loan, I was stuck in a financial situation and needed to refinance and pay my bills as well as start up a Business. I tried seeking for loans from various loan firms both private and corporate organisations but never succeeded and most banks declined my credit request. But as God would have it, I was introduced by a friend named Lisa Rice to Le_meridian funding service and undergone the due process of obtaining a loan from the company, to my greatest surprise within 48hrs just like my friend Lisa, I was also granted a loan of $216,000.00 So my advise to everyone who desires a loan, "if you must contact any firm with reference to securing a loan online with low interest rate of 1.9% and better repayment plans/schedule, please contact Le_meridian funding service. Besides, he doesn't know that am doing this but due to the joy in me, I'm so happy and wish to let people know more about this great company whom truly give out loans, it is my prayer that GOD should bless them more as they put smiles on peoples faces. You can contact them via email on {lfdsloans@lemeridianfds.com Or lfdsloans@outlook.com} or Text through Whatsapp +1-989 394 3740.

Unknown said...

No thanks at allllllllll

Post a Comment