antonyg
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| posted on 9/5/05 at 07:07 PM |
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which unions ???????????
hi, i am after some unions for my fuel pump similar to the ones on this website
http://www.rallydesign.co.uk/catalog/index.php?cPath=281_284
but am unsure what the 1/8 NPT means the threads on the pump i think are 3/8 fine thread are these any good or can someone recommend a good local
supplier
Thanks Antony
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Marcus
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| posted on 9/5/05 at 07:12 PM |
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The threads on the pump are likely to be NPT or BSP pipe threads. A 1/8 NPT or BSP is about the same OD as a 3/8 UNF bolt, sounds like you need some
Zeus tables!
Marcus
Marcus
Because kits are for girls!!
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antonyg
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| posted on 9/5/05 at 07:37 PM |
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when you say
" you need some zeus tables " what do you mean ?
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flak monkey
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| posted on 9/5/05 at 08:21 PM |
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There is a little book thats an engineers bible when it comes to threads....its called Zeus Tables and it contains all the info you could want to know
about most of the popular threads, also other handly little bits of knowledge....see here:
http://www.tooled-up.com/Product.asp?PID=6505
David
Sera
http://www.motosera.com
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Jonr
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| posted on 9/5/05 at 09:29 PM |
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hose / pipe unions will never be the same as a bolt thread. closeish but no cigar.
NPT threads are 'National Pipe Taper' so the easy way to tell them is that the threads are tapered. Look closely or get the vernier out
and and you will see the slight taper. They seal on the threads and usually require some sort of sealant, PTFE etc.
BSP is 'British Standard Parallel' and funnily enough the threads are parallel, so no taper. They have a metal to metal face seal, so on
the inside of a male fitting you will have a smooth concave cone, reverse on the female (hose end) They seal on this metal face so no sealant needed,
putting PTFE on them will generally stop them sealing or split the fitting.
mixing NPT and BSP is a recipe for disaster. A NPT fitting will go easily into a BSP one, it might even seal if you stick some PTFE on it but they
are likely to fail sooner or later. I work for an oil company and have seen some very nasty accidents happen because somebody forced the wrong types
of thread together.
NPT = Taper, seals on thread
BSP = Straight, seals on face.
Pretty certain that most fuel pumps, regulators etc are 1/8" npt
[Edited on 9/5/05 by Jonr]
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britishtrident
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| posted on 10/5/05 at 07:06 AM |
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BSP = British Standard Pipe thread this can be parrallel or tapered in which case it is reffered to as BSPT
Likewise the US standard taper pipe thread NPT has a parrallel sibbling NP
http://mdmetric.com/tech/thdform3.htm
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NS Dev
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| posted on 10/5/05 at 07:10 AM |
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was about to correct that one but you have done it for me Britishtrident!
Fuel fittings on british pumps (facets and the like) are either 1/8 npt (on the smaller ones) or 1/4 NPT (on the red top facet)
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antonyg
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| posted on 10/5/05 at 04:24 PM |
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thanks i think i know which ones to get now
cheers
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owelly
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| posted on 10/5/05 at 06:41 PM |
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As a point........for stuff smaller than 3/8" BSP or NPT, it's generally accepted throughout industry, that on low pressure aplications,
they can be interchanged. For 1/4" for example, the BSPT is 19threads per inch and the NPT is 18 tpi. Most pipe/plumbing stockists only stock
BSPT and insist they are the same as NPT!!!
http://www.ppcmag.co.uk
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