John the kiwi
Well-Known Member
To Scottie
Apologies for my ungracious comment on your contribution. (Note to self: avoid posting after a long working day and a couple of drinks!)
I work with BSP all the time in the piping of minor systems and connection of instruments but i dont have all the answers so this thread is interesting.
To Marsupial - yes of course you are right. In fact IIRC BSP nominal sizes were based on the internal diameter of cast iron pipes made in Victorian times.
Schedule 40 Pipe has a bore that is approximately the same as the nominal size, but this is way heavier wall thickness than people would normally use on boats.
Fact remains though that BSP has been adopted into the metric system.
NPT = National pipe Thread is an american equivalent system that works on same pipe Outside diameters but uses a different number of threads per inch (in all except one size)
Thread form is different too at 60 degrees for NPT but 55 degrees for BSP.
(People selling instruments and devices with NPT fittings in Metric countries are known to be motherless and will be first against the wall when the revolution comes
)
David 2452 - In terms of through hulls i am interested in your comment about using fibre washer to seal the end face. I have a thru hull and valve with no internal end face to seal against and dont think i have seen such a thing can you elaborate?
Finally a tip to anyone using teflon thread tape: You need to wind the thread tape on in the clockwise direction as you look at the end of the pipe.
This is much easier if you hold the thread tape roll so that is unwinding backwards as it were. Most people start by rolling the tape around as if it were normal sticky tape but this is wrong. Turn a it over so that the "back" of the tape is going onto the thread and you can then keep a constant tension on the roll by the friction of your fingers.
Start at the inboard end of the thread and work towards the end of the pipe or fitting.
It doesnt have a sticky side so it doesn't matter which way up it goes, but it is a lot easier backwards.!
Regards
Apologies for my ungracious comment on your contribution. (Note to self: avoid posting after a long working day and a couple of drinks!)
I work with BSP all the time in the piping of minor systems and connection of instruments but i dont have all the answers so this thread is interesting.
To Marsupial - yes of course you are right. In fact IIRC BSP nominal sizes were based on the internal diameter of cast iron pipes made in Victorian times.
Schedule 40 Pipe has a bore that is approximately the same as the nominal size, but this is way heavier wall thickness than people would normally use on boats.
Fact remains though that BSP has been adopted into the metric system.
NPT = National pipe Thread is an american equivalent system that works on same pipe Outside diameters but uses a different number of threads per inch (in all except one size)
Thread form is different too at 60 degrees for NPT but 55 degrees for BSP.
(People selling instruments and devices with NPT fittings in Metric countries are known to be motherless and will be first against the wall when the revolution comes
)David 2452 - In terms of through hulls i am interested in your comment about using fibre washer to seal the end face. I have a thru hull and valve with no internal end face to seal against and dont think i have seen such a thing can you elaborate?
Finally a tip to anyone using teflon thread tape: You need to wind the thread tape on in the clockwise direction as you look at the end of the pipe.
This is much easier if you hold the thread tape roll so that is unwinding backwards as it were. Most people start by rolling the tape around as if it were normal sticky tape but this is wrong. Turn a it over so that the "back" of the tape is going onto the thread and you can then keep a constant tension on the roll by the friction of your fingers.
Start at the inboard end of the thread and work towards the end of the pipe or fitting.
It doesnt have a sticky side so it doesn't matter which way up it goes, but it is a lot easier backwards.!
Regards
Last edited:
