BSP not what it seems

oldbilbo

oldbilbo

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A query for the real injineers among us....

I'd fondly imagined that through-hull, stopcock, and associated boaty fittings advertised as 'BSP' would be compatible. I needed to purchase a pair of 'equal 1 1/2" nipples' to join female threaded components, and was surprised to discover that all the other bits I had - old and new - were parallel threaded, while the nipples were tapered.... and could not be done up fully home. Only half the threads were engaged in the female part(s) of the assemblies.

A Google search, and a Wikipedia entry, advises that 'British Standard Pipe' has several variants, including BSPP ( Parallel ) and BSPT ( Tapered )
No info on whether ANY of the boaty products on chandlers' catalogues, or indeed on ( distributors ) Aquafax' website, is available. Sales staff, when queried about this, just look gormless and grunt....


nipple.jpg



So the query I have is, will it make a significant difference to my assembly of 'good' stopcockery? Will a surveyor suck his teeth and shake his weary head? How on earth will I get an adequate water-seal with only one thread-Turn engaged and locked up tight? :confused:
 
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Doesn't need an engineer, Enny Fule Kno that BSP comes in straight and tapered. But the bodgers put straight male threads into tapered female, which is Not OK.

Tapered male into straight female should be ok, with a couple of turns of teflon tape to lubricate it so you can do it up nice and tight. This will seal on the threads. If you'd bought a straight nipple, it would need an O-ring or fibre washer and smooth faces to squeeze it between, because two parallels are not designed to seal on the threads. Lacking that, perhaps you ended up with the right thing after all?

You should be able to get substantially more than one turn of thread on though. Teflon, and a bigger spanner!

ASAP list everything as either straight or tapered, as well as telling you what it's made of which chandlers are also rubbish at. So I don't look anywhere else.

EDIT: You've edited your post to add a picture of what you bought. It clearly says "tapered" in the description, and even looks tapered in the picture.

Pete
 
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prv said:
EDIT: You've edited your post to add a picture of what you bought. It clearly says "tapered" in the description, and even looks tapered in the picture. Pete
Click to expand...

Thanks, Pete.

You are right, of course. I added the pic some time after composing the post, finding it on a plumbing/pipe supplier's site while hunting the web for an 'explanation'.... That is similar to what I bought on Saturday morning, driving 80 miles out of my way to get my hands on the darned things so I could finish the job. bah!

I'm still surprised, but perhaps shouldn't be, to find that while all the components of the setup I inherited and those I've bought new are parallel thread and screw together without issue, the only component in the catalogues I have ( as far as I can now tell ) with a tapered thread is this double nipple thing..... which doesn't mate well with the other components. Why?
 
Ich bin ein ingeneur - or a berliner or a jelly donut or something.
Pet hate no 1 is bodgers and so called engineers who put thread tape on BSPP joints.
BSP Parallel threads need to seat on a face gasket.
BSPT = taper threads seals on the thread and need thread tape and or jointing compound.

However manufacturers are careless and buyer beware! Just today i bought a valve and nipple from the local plumbers merchant for the job i was working on.(OK i misunderestimated the Bill of Materials for the project by a tiny bit, so shoot me!) The barrel nipple i was first offered was so far undersize that i would have needed something like a whole roll of thread tape to make a bad seal. Pity the poor non engineer who bought this in good faith. I was able to confidently reject it and i and the shop guy found another that wasnt quite as bad.
Moral of the story is that you might not be as familiar with this stuff as a "pro" like me, but you may well be being offered rubbish components.
Your tapered males should engage to about 3/4 thread length inside a parallel female thread and seal well.
Cheers
 
scottie said:
A tuppence worth

Remember that the BSP sizes are based on the nominal bore size of steel pipe in imperial old money
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Sorry but not worth Tuppence and not very helpful.
BSP has been adopted wholesale into the metric system. I worked in Germany and routinely specified BSP as part of the project specs.
1/2 inch = 15 mm, 3/4 inch = 20 mm, 1" = 25 mm, 1 1/4 " = 32 mm, 1 1/2 " = 38 mm, 2" = 50 mm, 2 1/2" = 65mm, 3" = 80 mm etc.
I copied this from Wikipedia:
"Two types of threads are distinguished:

Parallel ('straight') threads, British Standard Pipe Parallel thread (BSPP; originally also known as[1] British Standard Pipe Fitting thread/BSPF and British Standard Pipe Mechanical thread/BSPM), which have a constant diameter; denoted by the letter G.
Taper threads, British Standard Pipe Taper thread (BSPT), whose diameter increases or decreases along the length of the thread; denoted by the letter R.

These can be combined into two types of joints:

Jointing threads: These are pipe threads where pressure-tightness is made through the mating of two threads together. They always use a taper male thread, but can have either parallel or taper female threads. (In Europe, taper female pipe threads are not commonly used.)
Longscrew threads: These are parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face, with the tightening of a backnut."

Hope this helps

Cheers
 
John the kiwi said:
Jointing threads: These are pipe threads where pressure-tightness is made through the mating of two threads together. They always use a taper male thread, but can have either parallel or taper female threads. (In Europe, taper female pipe threads are not commonly used.)
Longscrew threads: These are parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face, with the tightening of a backnut."
Click to expand...

Thanks - that matches my understanding of correct joints, as stated in post #2.

The interesting corollary is that practice with seacockery on European (including UK) boats rarely follows these engineering principles. I have only ever come across parallel-threaded skin fittings, onto which we screw a parallel-threaded ball valve. This is a joint that should have the face of the valve pressing a washer against a flange on the skin fitting, but no such flange is provided (and it wouldn't fit through the hole in the hull if it was). Using a nut as the flange doesn't work (though it's useful for locking purposes) because the interface between the nut and the skin fitting is not itself sealed. So we end up applying sealant (loctite etc) or worse, lots of turns of teflon tape, to try to make a seal on threads that are not designed for it.

At least the hose barbs on the other side of the valve are usually tapered.

Pete
 
John the kiwi said:
Sorry but not worth Tuppence and not very helpful.
BSP has been adopted wholesale into the metric system. I worked in Germany and routinely specified BSP as part of the project specs.
1/2 inch = 15 mm, 3/4 inch = 20 mm, 1" = 25 mm, 1 1/4 " = 32 mm, 1 1/2 " = 38 mm, 2" = 50 mm, 2 1/2" = 65mm, 3" = 80 mm etc.
Click to expand...

John, you misunderstand, the poster was highlighting the fact that BSP pipes and fittings are sized by the imperial system of system of measurement based on the inside diameter of the bore not the outside diameter of the tube. So your 1/2" or 15mm (which it isnt!) tube has and OD of 3/4". When the EU got hold of BSP fittings they did n't know what to do, so instead of changing the pipe sizes they fudged it and 12.5 mm became 15 mm and so on (they changed the size of a mm if you want to be precise). The pros in the trade in the UK took no notice of all this and we continued to specify and supply pipes and fittings in the correct way - or at least until I left the trade in 1989 after that I have no idea what they did but the fittings I buy now are still BSP and are in every respect imperial. The USA has a slightly different thread profile - I think.

cheers
 
What has to impress is the long life of the imperial BSP system, whoever designed it must have known what they were doing.
 
Thanks to 'John t.k.', 'prv', and 'marsupial' ( whom I imagine is some other kind of strange antipodean! Sheeesh! They're everywhere now, looking for runs and wickets, and ashes.... ), and others trying to help.

Please to permit a mini-rant.... :mad:

This 'bear of little brain' wants only to keep the ocean on the outside and would expect, when seeking to purchase 'mission critical' products from chandleries and their trade suppliers, the beggars should at least know what they're selling AND MAKE IT CLEAR AND UNAMBIGUOUS on their packaging/websites/catalogues so peeps like me can decide if more info is needed to make a sound, informed - and safe - buying decision.

The through-hull fittings and the stopcocks I purchased have parallel threads. They fit together just fine. However, engine bits get in the way and I need to use an 'equal socket' and this 'equal nipple' thingy to raise the stopcock beyond the obstruction - as was the original setup. All the other bits are 'parallel thread' except this 'equal nipple'. Nowhere in the seller's and their supplier's info is any differentiation made - it's all called simply BSP - and more than half the 'equal nipple' threaded portion is unusable, at both ends. That's not good enough, and is IMHO misleading.

I appreciate peeps trying to help by suggesting I make the best of a bad job by winding multiple layers of Teflon tape around the darned things, packing out the gaps, but how many layers is enough, and how does one get short, stubby fingers into long, constrained nooks while holding a couple of yards of 'electrostaticly-charged' tape between finger and thumb? I reckon I'd need fingers like ET! And I certainly can't get two Stilsons - big enough to open to the hex-nut size of 55mm - into the space, 'cos there's lots of engine bits in the way. I'm working at full armslength, using two chain wrenches. Maybe I'm not cut out for 'hanzon injineerin'.... :rolleyes:

The burble about fluctuations in SIs being expressed in 'old money' is all very well, but I pay in new money - and rather a lot of it. As I recall, before 'That'll do. No-one will notice' became a mantra, one-half-inch equated to 12.7mm - or has the EU mucked that up, too?

Grrr! :mad:
 
oldbilbo said:
whom I imagine is some other kind of strange antipodean! Sheeesh! They're everywhere now, looking for runs and wickets, and ashes....:
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to put you out of your misery Marsupial is British - well English; born in London to parents who were also born in London as were their parents back to at least 1700 where the records run out.

Marsupial was a password to a school IT system chosen because even if the kids overheard it they would never be able to spell it, it lasted for many years without hacking. It became a screen name on here by mistake and has stuck ever since.

not much help but I agree with all your comments about "chandlers" not knowing what they're selling. Obviously I cannot know what you are up against but perhaps a box spanner could take the place of one of the wrenches and afford you some space.
 
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To do what you want to do, ie join 2 female fittings, you might find a "running nipple" useful. (careful with the googling! ) Use it with a couple of backnuts and soft washers. These are usually parallel BSP and can be shortened if need be.
Incidentally, Female taper threads do exist, but are not common.
 
I find that when using valves to a skin fitting that the correct size good quality fibre washer internal in the valve gives a reliable seal even on the small face provided by the skin fitting. A little sealant on the threads as a lubricant to aid control over the tightening, not as a sealant makes it easier in confined spaces.
As for chandlers, most people stopped using the ones where knowledgeable interested people who were (are) able to give good advice predominated in favour of box shifters with little or no interest in the components being discussed here, so it's no real surprise that they found survival difficult and are as a result fewer and fewer.
 
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David2452 said:
As for chandlers, most people stopped using the ones where knowledgeable interested people who were (are) able to give good advice predominated in favour of box shifters with little or no interest in the components being discussed here, so it's no real surprise that they found survival difficult and are as a result fewer and fewer.
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In general I've found the folk at both my local Force 4s definitely interested and fairly knowledgeable. Certainly very impressive a few weeks ago when a lady came in for a kill-cord but didn't realise there were different types and didn't know which one she needed. The young guy helping her called to his colleague at the till -

"John, do you know what kind of kill-cord they have on the XYZ Club safety boat?"
She looked surprised - "how did you know what boat it was for?"
"I remember seeing you come past me on the river earlier in the week"
Meanwhile 'John' (can't remember his actual name) on the till was thinking deeply, and announced "They have an ABC kill cord on that boat".
The lady was even more surprised - "how on earth did you know that?"
"Oh, I drove it for a couple of events last year."

So definitely not uninterested box-shifters there.

Mind you, in the past they were poor about mixing up their brass/bronze/DZR fittings in open bins. I think they've got better at that since the issue became more widely known. They do still stock a lot of plain brass though, with nothing suggesting it's not a good idea for underwater use. Fine in small sizes for fuel and freshwater plumbing, but what is the average leisure sailor going to do with a 1-1/2" brass elbow except use it inappropriately for seawater?

Pete
 
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