ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Metric threads

The nominal diameter is the internal one and the external dimension includes the thickness of the pipe walls. I came across a curious difference in the US where brass compression fittings are quoted using the external diameter of pipe! I couldn’t find a ¾” union (for ¾” copper pipe) I needed until I was directed to the 7/8” ones.

The metric world adopted the British Standard Pipe (BSP) thread as the ‘metric’ standard. The diameters are sometimes quoted in mm but the thread pitches are in rational units of threads per inch (tpi) – that should make Paul smile .

The US of course uses National Pipe Thread (NPT) which has different thread pitches than BSP thus they are once again different from the metric world.

Then there are the lamp thread pitches just to keep this subject on topic. The same threaded tube for table lamps etc is used in both South Africa and the US. It is called 1/8” ISP in the US but has a diameter of ~3/8” (~10mm) and a thread pitch of 27 tpi. In this case the internal diameter is well in excess of 1/8”.

Hutch,
Good point!.
In some cases with Plumbers using nasty old busted pipe threading gear that thier Grand- fathers used and abused, it's a wonder that the pipes didn't leak like a sieve here.
I learned how to thread pipes with a machine called a Thred-All and the pipe was held in a Pipe Vice.
Yes even to this day we still use the TPI nomenclature here.
Even, I must agree that there hasn't been a Brass fitting used here that doesn't use the Imperial sizing of either 3/8" or even 1/2" (outer diameter).
I went to buy some Brass recently for a guy I was building a 430MHz Ham Aerial for.
I needed some 8mm square stock for a T-Match and when I told the guy what size I wanted, he looked at me as though I'd sworn in Church.
He then informed me that I would be needing 5/16" stock, with rounded edges, no less!.
Good Grief!.
I felt like saying to him,"Could you please put the corners back on, it has to be square".
But let's not make life harder, eh?!.

Oh yes, I remember details like that for when somebody tries to tell me that "everything" is made to metric specifications these days!

Copper water pipe in Britain underwent the change from inch to millimeter specifications, and in doing so also change from inside bore to outside diameter measurements. Hence an old 1/2-inch pipe is almost the same as a modern 15mm type, and is certainly close enough to be interchangeable in a compression fitting. Unfortunately, the changes to some of the larger size were not so convenient and necessitate the use of adapters when coupling up new pipes to an old system.

We're going to metric speed limits this month

See http://www.gometric.ie/ for the huge count down clock and explanation of how they're going to do it.

I still don't believe they'll manage to do it as smoothly as they're suggesting!

I knew that metric speeds were coming to Ireland, but hadn't realized it was this month.

I have to ask why? I would have thought most people would be happier for the money to spent on something useful.

What genius came up with this idea?

Now I've heard it all -- Metric speed limits are safer. I'd like to know how they managed to come to that conclusion.

The major safety change is the reduction of speed limits on minor roads (R-regional and L-Local) to 50 mph (80km/h) (they were 60mph)

They've also done away with a general 60 mph speed limit. i.e. every road will have a set speed limit.

They basically modernised the speed limit legislation to improve safety while converting to metric limits at the same time.

They could have done it years ago with MPH too.. it's partly spin and partly practicality .. i.e. if they're going to be changing all the speed limit signs, they may as well take the opportunity to review the actual limits as well as converting them.

There is absolutely no plan to convert to European style road signs though. All we're doing is replacing signs that clash.

i.e. in Ireland a symbol in a red circle = do it.. red circle crossed out = don't do it (quite logical)

in the rest of Europe red circle = forbidden.
white symbol on blue background = do it / permitted to do it.

So we're keeping our negative system i.e. red circle crossed out = don't do it.
and replacing the positive signs with Euro-style white symbol on blue background.

The yellow diamond warning signs are staying, as are the yellow lines marking hardshoulders and various other unique-to ireland systems as they don't cause any confusion.

--- there's also a few other marking systems that im not sure if they're unique to here or not.

The reflectors on the road on the outside are normally yellow... if a junciton is coming up they change to green for 300 meters before the junction (on the side of the junction) Junctions are also marked out by 3 green bollards thesedays too.

If a sharp bend is approaching, the cats eyes reflectors turn red on the side of the bend.

Actually works quite nicely, but isn't installed on all roads, only newly built / refurbished ones.

----

Also, the National Roads Authority had a VERY odd approach to motorway / dual carriage way design. They didn't like crash barriers in the centre! And instead, built most motorway / dual carriage way with a 20 meter wide centre median... the logic being that if you had the space, it was preferable to have a huge inclined median rather than a crash barrier as it would give you a much softer landing.

However, this logic was based on 1950s US studies! when cars moved a lot slower and we had several very bad accidents where trucks managed to plough across 20meters of sloping grass...

They've now had to retrofit many hundreds of KM of crash barriers to these enormously wide motorways.

They've also discovered that if you build the motorways with narrower medians, and with suitable crash barriers you actually save about 50% of the cost!



There is NO barrier on that motorway! it has had to be retrofitted recently.

sorry for poughing so far off topic... but it just amazes me how these things happen!

[This message has been edited by djk (edited 01-04-2005).]

Sure. Full marks for using common sense in making the changes together (the British govt. would probably have done it seperately at twice the cost! ), but to say the change to km/h is responsible for improving safety is just ridiculous.

Yep, much more logical and consistent than the stupid signs we're stuck with here. No left/right/U-turn has the cross through, but the others don't. Visiting Americans, Australians, etc. must have a hard time trying to figure out our signs.

Good, I prefer them to the red-bordered triangles as they seem to stand out more.

They struck me as odd first time I visited Ireland -- It was like driving on the exact opposite of U.S. highways with yellow center lines and white edge lines, although of course we're used to lots of yellow no-parking lines in towns here!

Makes sense that they match the line, which the reflectors here sometimes don't. Motorways here use white lane refelctors, amber on the far right edge by the barrier or median, red on the left shoulder . The red changes to green at exit ramps.

Again, must be rather off-putting to American tourists.

Yep, apologies to C-H. Way off topic and criticizing European road signage as well!




[This message has been edited by pauluk (edited 01-05-2005).]

Oh, well, I suppose I'll just continue down the road...

The Swedish road authorities have been surprisingly quick in adopting changes. New types of poles(*), changing from bulbs to LED's in traffic lights etc. were done in no time. Latest change is that all exits have become numbered, which is something other parts of the world have had since stone age.

Another novelty is the wire rail in the centre. It is designed to give way if you drive into it, preventing the car from bouncing and spinning around. It effectively absorbs the energy of the vehicle and has been sucessful in reducing fatal accidents.

Then we have this odd type of road used to save money: One lane in each direction plus a center lane that alternates between the directions. For maybe a kilometre, the northbound traffic has two lanes and then the southbound traffic has two lanes for a kilometre instead.

(*) A single square pole instead of multiple round poles is used behind new signs. They have changed the method of anchoring (???) them in the ground as well, from concrete to simply driving a winged steel "anchor" into the ground.

That's not saving money! You should try a Rhodesian (long now Zimbabwean) strip road. It's essentially a dirt road with a single one-car width of tarmac down the middle. Drive like the clappers until something come the other way and then, at the last minute, both vehicles pull half onto the dirt with the centre-road wheels still on the edge of the tarmac. resume high speed travel thereafter.

If you really want to get cheap ten lay two thin strips of tarmac to act as the fast route - one for each side's pair of wheels.

Ian

PS To get this sort of back on topic - before Zimbabwe used candles, it had electricity.

[This message has been edited by Hutch (edited 01-07-2005).]

C-H. that type of "1+2" lane road system with the wire centre barrier is also being introduced in ireland. the plan is to have it on all major roads that don't warrent being widened to motorway / dual carriageway.

Paul: the logic of the yellow lines on the edge of roads is that in poor visibility you clearly identify the edge of the road as the outer edge and not another lane.

Also, on the exit numbering system. cork and dublin city councils have gone completely mad and numbered half the city's street junctions creating orbital routes with the most confusing signs i've ever seen anywhere.

Outer orbtal

inner orbtal.

these are the new simplified signs. the first version was so confusing they were banned by the department of transport!

the banned version



note: they even put An Lar (city centre in Gaelic) which is as widely spoken in Dublin as it is in Paris and New york.



Hundreds of these had to be removed and replaced! Cost a considerable amount of money and time.

people assumed they were secret codes put up to help UFOs find their way around town!

[This message has been edited by djk (edited 01-08-2005).]