Exhaust fittings

[Mark R]

32 minutes ago, ditchcrawler said:

Are you sure its 1½" and not 2" before you order

 

14 minutes ago, Alan de Enfield said:

 

 

 

Remember that BSP thread sizes ARE NOT the actual measured size.

 

Look up on line the BSP size vs the actual OD.

 

There is some weird formula like "deduct 25% of the BSP stated size, to get the actual size".

 

So if your existing pipe measure 1 1/2 inches overall you need 2" BSP.

 

BUT - check on line.

 

 

The exhaust flange on my engine is 1 1/2", measured at about about 48mm OD. There is no increase in pipe size between the flange and exhaust. So I'm right in assuming it's 1 1/2" BSP. There's no weird marine thing going on?

[Alan de Enfield]

3 minutes ago, Mark R said:

 

 

 

The exhaust flange on my engine is 1 1/2", measured at about about 48mm OD. There is no increase in pipe size between the flange and exhaust. So I'm right in assuming it's 1 1/2" BSP. There's no weird marine thing going on?

 

 

Yes, when measured, 1 1/2" OD  is 38mm, not 48mm

 

But the OD of a male 1 1/2" fitting is 48mm.

 

[David Mack]

41 minutes ago, Alan de Enfield said:

Look up on line the BSP size vs the actual OD.

 

There is some weird formula like "deduct 25% of the BSP stated size, to get the actual size".

 

So if your existing pipe measure 1 1/2 inches overall you need 2" BSP.

 

BUT - check on line.

The BSP nominal size is the bore of thick walled steel pipe that was used when the standard was established - modern pipe has the same outside diameter but thinner wall, so the inside diameter is larger than the nominal size. For the sizes used in exhaust systems the pipe OD will be around 0.25" larger than the nominal size, and the fittings will be bigger than that. As Alan says, check before buying.

[Mark R]

The threads are definetly 1 1/2", thanks for the heads up though. Do threaded fittings require a jointing compound (exhaust paste or similar) when assembling?

[BEngo]

4 hours ago, Mark R said:

The threads are definetly 1 1/2", thanks for the heads up though. Do threaded fittings require a jointing compound (exhaust paste or similar) when assembling?

Yes,  if you ever want to get them apart.  The stuff you want is Coppaslip  or other copper grease.  Liberally coat all of the threads, male and female.  Wipe the excess off after it is all tightened up.

 

An alternative is an MS2 paste containing Molybdenum Disulphide.  Use as with copper grease.

N

 

[Ronaldo47]

As far as I know, screwed iron pipe is still in principle available in three types: light,  medium, and heavy  (gas, water, and steam respectively), and two finishes (black and galvanised).   The outside diameters of all types are the same for a given size, the heavier types having smaller bores than the lighter types.

The male thread on plain pipe and most male fittings  is usually taper,  whereas female threads are parallel. Pipe and fitting are usually maleable, so that,  when wrenched up tight, the male and female  threads yield slightly and inimately engage over several turns rather than just at the point where their respective inner and outer diameters are the same, thereby  providing a good seal.

 

Parallel male threads are used for the long thread of a running coupler and on taps and ball cocks. For the latter two, a fluid-tight, easily disconnectable, connection can conveniently  be made using a flanged coupler with threaded coupling nut and a (fibre) washer to make the actual seal,  rather than the thread. 

 

 

Edited September 30 by Ronaldo47
typos

[ditchcrawler]

I have a cou[le of these on my system 

[Mark R]

31 minutes ago, BEngo said:

Yes,  if you ever want to get them apart.  The stuff you want is Coppaslip  or other copper grease.  Liberally coat all of the threads, male and female.  Wipe the excess off after it is all tightened up.

 

An alternative is an MS2 paste containing Molybdenum Disulphide.  Use as with copper grease.

N

 

 

@BEngo, From what you are suggesting I don't need a jointing compound (to ensure gas tightness), just lubricant to allow disassembly?

 

26 minutes ago, Ronaldo47 said:

As far as I know, screwed iron pipe is still in principle available in three types: light,  medium, and heavy  (gas, water, and steam respectively), and two finishes (black and galvanised).   The outside diameters of all types are the same for a given size, the heavier types having smaller bores than the lighter types.

The male thread on plain pipe and most male fittings  is usually taper,  whereas female threads are parallel. Pipe and fitting are usually maleable, so that,  when wrenched up tight, the male and female  threads yield slightly and inimately engage over several turns rather than just at the point where their respective inner and outer diameters are the same, thereby  providing a good seal.

 

Parallel male threads are used for the long thread of a running coupler and on taps and ball cocks. For the latter two, a fluid-tight, easily disconnectable, connection can conveniently  be made using a flanged coupler with threaded coupling nut and a (fibre) washer to make the actual seal,  rather than the thread. 

 

 

 

@Ronaldo47 I'm thinking of using 316 stainless steel, I'm assuming that's ok as a material? Appreciate your insight into threads.

 

@ditchcrawler do you use though to provide a means of easy disconnection?

 

 

[Peugeot 106]

I used high temp silicone as used in wood burners so that I could orientate the fittings,( a bit like using ptfe on low temp). Never used it but presume exhaust paste is similar. But if you use couplings you won’t need to use them

[Ronaldo47]

I'm afraid I have had no experience of plumbing with stainless steel. According to Building Research Establishment leaflet 16 (1973 edition), thin wall stainless steel pipes were then  available in the same sizes as metric copper pipe, and could be joined by soldering or by compression joints. I think copper was expensive or in short supply at the time, and I have never come across any SS  piping in domestic properties. 

[BEngo]

The seal is (should be) formed by the  tapered Male threads into parallel female threads, so no need for joint sealer.

 

Youvwant to prevent corrosion in the ttreads, in order to be able to dismantle.

 

Syeam and water are much better behaved than exhaust, for some reason I don't understand, but probably involves carbon and acid gases.

 

 

N

[ditchcrawler]

19 hours ago, Mark R said:

 

 

 

 

@Ronaldo47 I'm thinking of using 316 stainless steel, I'm assuming that's ok as a material? Appreciate your insight into thread

 

 

Like this or threaded pipe, Have you got to weld the flange for the manifold?

 

19 hours ago, Mark R said:

 

@ditchcrawler do you use though to provide a means of easy disconnection?

 

 

No, with one end fixed to the roof and the other to the engine its the easiest way to put it together.

[cuthound]

20 hours ago, Ronaldo47 said:

I'm afraid I have had no experience of plumbing with stainless steel. According to Building Research Establishment leaflet 16 (1973 edition), thin wall stainless steel pipes were then  available in the same sizes as metric copper pipe, and could be joined by soldering or by compression joints. I think copper was expensive or in short supply at the time, and I have never come across any SS  piping in domestic properties. 

 

The central heating system in my last house used stainless steel piping. That house was built in 1972.

[Ken X]

We have a stainless steel exhaust on our Morris Minor. When new it was much noisier than the standard item as it rang and crackled on overrun presumably due to being a stiffer material. Many years later it has mellowed nicely, due, I guess, to a build up of carbon inside.

It will be interesting to see how noisy a stainless boat exhaust is compared to black iron.

[ditchcrawler]

34 minutes ago, Ken X said:

We have a stainless steel exhaust on our Morris Minor. When new it was much noisier than the standard item as it rang and crackled on overrun presumably due to being a stiffer material. Many years later it has mellowed nicely, due, I guess, to a build up of carbon inside.

It will be interesting to see how noisy a stainless boat exhaust is compared to black iron.

I had on on a Rangerover made to measure, a lot cheaper than a genuine RR one and lasted all the time I had the motor

[Mark R]

11 hours ago, Ken X said:

We have a stainless steel exhaust on our Morris Minor. When new it was much noisier than the standard item as it rang and crackled on overrun presumably due to being a stiffer material. Many years later it has mellowed nicely, due, I guess, to a build up of carbon inside.

It will be interesting to see how noisy a stainless boat exhaust is compared to black iron.

 

@Ken X I'm assuming black malleable iron is the standard then?

[hider]

Threaded black iron is the normal system on narrowboats. I would not use a thin wall stainless system as used on cars. Stainless is more prone to fatigue cracking and the vibration of a diesel engine feeding into a rigidly secured exhaust attached to the hull would not be good even with the flexible section.

Why try to reinvent the wheel? Just use cheaper iron fittings and pipe, it will likely see you out.  What you have at present looks to be at least 40 years old.

[Ken X]

I'm not sure there is a standard although others may be better informed. Edit (see above)

 

Most boats I've seen look like the boat was built and when the budget ran out they realised the exhaust was missing. Cue a rapid furtle around the yard for some gash pipe and "voila" one custom exhaust. 😄 

Edited October 2 by Ken X
Simultaneous post.

[Peugeot 106]

1 hour ago, Ken X said:

I'm not sure there is a standard although others may be better informed. Edit (see above)

 

Most boats I've seen look like the boat was built and when the budget ran out they realised the exhaust was missing. Cue a rapid furtle around the yard for some gash pipe and "voila" one custom exhaust. 😄 

Agreed. Maybe it’s time for someone to write up a guide on exhaust systems and how to connect them. I’ve seen guides for wet ones but nothing on Narrowboat dry systems. Regret it’s outwith my pay grade

[Tony Brooks]

1 hour ago, Peugeot 106 said:

Agreed. Maybe it’s time for someone to write up a guide on exhaust systems and how to connect them. I’ve seen guides for wet ones but nothing on Narrowboat dry systems. Regret it’s outwith my pay grade

 

I am very tempted to say that if you need a guide on assembling a selection of ion pipe fittings, the silencer and flexible section then perhaps the job is beyond you (not you @Peugeot 106). But then welding may also be involved.

 

The trouble with writing a guide is that there are so many variations in how the silencer is orientated, where the hull outlet is, where the exhaust fits onto the engine, and so on. The, as has been mentioned in this topic, there are the non-intuative way such pipes are sized and the way the angle of some fittings are described.

[Peugeot 106]

34 minutes ago, Tony Brooks said:

 

I am very tempted to say that if you need a guide on assembling a selection of ion pipe fittings, the silencer and flexible section then perhaps the job is beyond you (not you @Peugeot 106). But then welding may also be involved.

 

The trouble with writing a guide is that there are so many variations in how the silencer is orientated, where the hull outlet is, where the exhaust fits onto the engine, and so on. The, as has been mentioned in this topic, there are the non-intuative way such pipes are sized and the way the angle of some fittings are described.

I was thinking of tips to disassemble the old one, sizing and design of the the new silencer  and avoiding back pressure or the possibility of water draining into the exhaust. Materials ie black iron normally and tricks for orientating the fittings (exhaust paste, high temp silicon, glass rope) or couplings.   Copper slip so that you can get things apart again. Flexible pipe to avoid vibration. Glass tape to avoid burn danger. Explanation of hospital silencers. 

I’ve never seen anything written for narrowboats though there is quite a lot for wet exhausts. I avoided the pratfalls back pressure and water ingress by luck! I’ve only fitted one exhaust system so am afraid that’s why it’s above my pay grade. It was just a thought. You’ve done enough I’m not expecting you (or anybody else) to do it but it could be a nice to have an introduction as it has different problems to fuel, oil, waste or water pipework.

There must be literature on how to (practically) size and fit exhausts 

 

 

[Tony Brooks]

2 minutes ago, Peugeot 106 said:

I was thinking of tips to disassemble the old one, sizing and design of the the new silencer  and avoiding back pressure or the possibility of water draining into the exhaust. Materials ie black iron normally and tricks for orientating the fittings (exhaust paste, high temp silicon, glass rope) or couplings.   Copper slip so that you can get things apart again. Flexible pipe to avoid vibration. Glass tape to avoid burn danger. Explanation of hospital silencers. 

I’ve never seen anything written for narrowboats though there is quite a lot for wet exhausts. I avoided the pratfalls back pressure and water ingress by luck! I’ve only fitted one exhaust system so am afraid that’s why it’s above my pay grade. It was just a thought. You’ve done enough I’m not expecting you (or anybody else) to do it but it could be a nice to have an introduction as it has different problems to fuel, oil, waste or water pipework.

There must be literature on how to (practically) size and fit exhausts 

 

 

 

If you look at the size of the exhaust pipes on cars with similar engine sizes, then you will see they are very much smaller than those on typical narrowboats, so the chances of increasing the back pressure to a detrimental lever with the pipework is probably slim. Especially if bends rather than elbow fittings are used.  Ideally one would have a swan neck as per wet exhaust boats, but often there is not enough space height wise on narrowboats.

[Peugeot 106]

6 minutes ago, Tony Brooks said:

 

If you look at the size of the exhaust pipes on cars with similar engine sizes, then you will see they are very much smaller than those on typical narrowboats, so the chances of increasing the back pressure to a detrimental lever with the pipework is probably slim. Especially if bends rather than elbow fittings are used.  Ideally one would have a swan neck as per wet exhaust boats, but often there is not enough space height wise on narrowboats.

Just the sort of valuable info we need!

[jacko264]

If it was me removing the straight pipe from the elbow I would heat the elbow  and using two  hammers tap round the elbow  then try and move with. Stillsons

make sure  you use safety  goggles as hot rust may come off  the pipes 

G