4.5 inch flue elbow

[tove]

Does anyone know if it's possible to get an offset 45 degree elbow for a 4.5 inch flue pipe?

Many thanks.

[Tracy D'arth]

Only in Malleable iron BSP screwed fittings, 4" or 5" I think, expensive.

 

Everyone just cuts the pipe at 22.5 degrees, rotates half a turn and welds back together.

[tove]

Thanks for the response Tracy. Actually it now seems that the slope isn't going to be as bad as I thought so am hoping the flue can run in a straight line. It is a bit bizarre though that 4.5 inch pipe is fairly common on boats and there are no elbows or bends available. Hey ho.

[Bee]

Most of us cut the pipe at more or less 22.5 degrees then spend ages and loads of rods filling up the gap with great lumps of weld before grinding it all back to what it would have been if we'd have cut it properly.

[tove]

1 minute ago, Bee said:

Most of us cut the pipe at more or less 22.5 degrees then spend ages and loads of rods filling up the gap with great lumps of weld before grinding it all back to what it would have been if we'd have cut it properly.

Lol. Yes, I've had some experience of this.

[magnetman]

114.3mm (4.5") butt weld fittings would work if you have welding options. 

 

Perhaps you could slice a 90 degree elbow to the correct angle with a slitting disc then weld it in. 

 

https://www.lockinex-store.com/weld-elbow-114-3mm.html

 

 

They are nice smooth bends which would give uninterrupted gas flow which is helpful. 

 

 

Edited September 12, 2020 by magnetman

[Tracy D'arth]

Part of my time served was as a fitter and engineer, after a while you learn to mark out correctly, cut accurately and weld properly, its all experience.

3 minutes ago, magnetman said:

114.3mm (4.5") butt weld fittings would work if you have welding options. 

 

Perhaps you could slice a 90 degree elbow to the correct angle with a slitting disc then weld it in. 

 

https://www.lockinex-store.com/weld-elbow-114-3mm.html

 

 

 

Oh, that is even more difficult I think, never tried it.

[magnetman]

I've not tried it either but did once manage to construct a flue with two small angles in it by cutting and welding the pipe. Worked ok actually. 

 

Ideally of course if possible you want a flue to be straight anyway. Adding bends just complicates things if you need to replace the flue later due to corrosion. 

 

It's nice having a straight flue you can just lower in from outside straight onto the stove and cut it off level with the top of the collar. Easy job. 

[BEngo]

2 hours ago, magnetman said:

114.3mm (4.5") butt weld fittings would work if you have welding options. 

 

Perhaps you could slice a 90 degree elbow to the correct angle with a slitting disc then weld it in. 

A band saw would be best, but if you have a band saw it is easier to cut and shut the pipe and only have one weld to make.

When making single plane cranked chimneys I have always found it a good idea to draw the pipe full size on the floor with chalk and to add bisecting lines to a

the angles.  Then lay the pipe on the drawing and  use the bisecting lines as a guide for a 9in grinder and zip  cutting disc.  If you get it wrong Bee's solution is good, but heavy on welding rods!  Always tack the pipe to shape and then try in the stove and collar.  Adjust and recheck before finally welding up, big gaps or no.

 

Skewed  cranked chimneys are something completely other?

 

N

[Bee]

2 hours ago, magnetman said:

114.3mm (4.5") butt weld fittings would work if you have welding options. 

 

Perhaps you could slice a 90 degree elbow to the correct angle with a slitting disc then weld it in. 

 

https://www.lockinex-store.com/weld-elbow-114-3mm.html

 

 

They are nice smooth bends which would give uninterrupted gas flow which is helpful. 

 

 

Now that is a lovely thing and really useful if you have a stove where the flue comes out of the back. Will v. soon be selling a pipsqueak stove with a small stub of cast iron pipe coming out of the back, that might fit over the stub and bolt in place. 

[magnetman]

I used a 316 stainless steel weld elbow aka mandrel bend for car exhausts for that job on a stove with a 70mm ID horizontal outlet. It just slotted inside no problem and the swaged flue went inside the other end of the mandrel bend. Perfect. 

 

The funny thing was I bought a 316 on eBay they sent a 304 so I messaged saying "this is a 304 not a 316". They sent me the 316. So two for price of one. 

 

Out of curiousity I tried it again a while later and same thing happened. This time I got a refund rather than the correct item. 

 

You do want 316 for a flue bend ideally. 

 

 

https://www.ebay.co.uk/itm/90-Degree-1D-Tight-Radius-Elbow-Stainless-316-Dull-Polish-Mandrel-Bend-Exhaust-/352784356510

 

 

They are printed with specifications so if they send you a 304 then DO mention it to them... I'm sure it was a deliberate strategy rather than an error...

 

They are thinner than the butt weld things but if it's 316 I reckon it'll be fine. 1.5mm wall I think it was so not incredibly thin. 

Edited September 12, 2020 by magnetman

[Batavia]

6 hours ago, magnetman said:

114.3mm (4.5") butt weld fittings would work if you have welding options. 

 

Perhaps you could slice a 90 degree elbow to the correct angle with a slitting disc then weld it in. 

 

https://www.lockinex-store.com/weld-elbow-114-3mm.html

 

 

They are nice smooth bends which would give uninterrupted gas flow which is helpful. 

 

 

45 degree butt weld elbows to ASME 16.9 / BS 1640 are also standard pipe fittings.

 

Chris G

[magnetman]

I thought they would be but was unable to find one on Google searches at that size. 

[Batavia]

25 minutes ago, magnetman said:

I thought they would be but was unable to find one on Google searches at that size. 

If the 4.5" refers to the OD of the pipe, then these people (and many other industrial pipe & fitting suppliers) have them:

https://www.valvestubesfittings.com/welding-pipe-fittings/butt-weld-fittings-bs1965-en10253/en-10253-butt-weld-45-degree-elbows-long-radius

 

They will be in carbon steel (or stainless, if you are feeling affluent), so ensure that you have a suitable weld procedure for welding the elbow to the pipe!

 

Chris G

ETA Confusion may be caused because many pipe fittings are specified by the Nominal Bore of the pipe, not its OD.

Edited September 12, 2020 by Batavia