Exhaust thread tape - 1GM10

Topcat47

Topcat47

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I think this is probably one for Viv Cox, but anyone with ideas, please chip in. I have a high level exhaust, consisting of a Bronze /DNZ mixer onto a brass male to male transition piece itself into the Yanmar 90degree elbow fitting (cast iron). Yes I know it's a materials nightmare. A couple of years ago I employ a jobbing engineer to fit a new casting and transition piece while I was in hospital. It leaked. I've taken it off and cleaned it up. In order to get the mixer positioned clear of the engine, he's used ordinary PTFE plumber's thread tape. There's not a lot left. Normally I'd use blue hylomar on the threads of the transition piece but if I tighten the three pieces up dry, the mixer fouls the head and there's no room to connect the exhaust pipe. Hylomar's not going to help in this case as I need to wind the mixer or the transition piece about 90 degrees back.

What do I use to fill the gap? the threads do need to be tight in the fittings.
 
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I'm not sure what you mean by there not being a lot of PTFE tape left. Is that the joint that leaked? Did the engineer put too little tape on?

I don't see why PTFE tape or another plumbers sealing compound like plumbers mait wouldn't work unless the thread is very loose.

Richard
 
If I understand you correctly if you tighten the fittings up dry (without packing the threads) they end up pointing in the wrong direction ?
Can you fit a lock nut on one of the male threads and tighten the other threads up normally with your preferred sealant then lock the last thread pointing correctly using the lock nut.
https://www.asap-supplies.com/catalogsearch/result/?q=1+1%2F4"+lock+nut
Not sure of your thread size.
Pete
 
Hi Guys,

The transition piece is ~ 1 7/8" bsp both sides and the thread is slightly tapered. It goes to the bottom on the injection manifold thread so I'm content to use Blue Hylomar there as a sealant. The transition piece does hard into the cast iron elbow eventually, but in order for the exhaust to clear the head, I need to wind it back about 1/4 turn from "tight", hence the need for something like thread tape to make the joint gas tight and stiff. I can't find a source of suitable copper washers to slip between the mixer and the transition piece to allow this to be done on that face.

The locknut would be a good idea if they have one suitable, or even a plain washer, I'll have to phone tomorrow. It would have to go on the mixer side. The thickness may be critical too and I don't have a milling machine to thin it down.
 
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Topcat47 said:
Hi Guys,

The transition piece is ~ 1 7/8" bsp both sides and the thread is slightly tapered. It goes to the bottom on the injection manifold thread so I'm content to use Blue Hylomar there as a sealant. The transition piece does hard into the cast iron elbow eventually, but in order for the exhaust to clear the head, I need to wind it back about 1/4 turn from "tight", hence the need for something like thread tape to make the joint gas tight and stiff. I can't find a source of suitable copper washers to slip between the mixer and the transition piece to allow this to be done on that face.

The locknut would be a good idea if they have one suitable, or even a plain washer, I'll have to phone tomorrow. It would have to go on the mixer side. The thickness may be critical too and I don't have a milling machine to thin it down.
Click to expand...

Where and how are you measuring 1 7/8"? Suspect that what you've actually got is 1 1/2" BSP, which goes by the size of the nominal bore. (Just in case you phone someone, looking for a locknut).
 
Hi
The lock nut may be a problem on a 1 7/8" thread. What about filing or grinding off one of the the male thread ends a touch so that it bottoms out in the correct position.
I am pretty sure the engine seacock on my Hunter 27 had been screwed onto epoxy resin on the threads and probably left to set in the correct position but I know epoxy doesn't like heat.
Pete

Just seen Normans post 1 7/8" does seem big for a 1 GM10 exhaust
 
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I've found my Zeus book, the transition piece is simple 1 1/2" BSP thread (~12 tpi), so there's a locknut in the catalogue. the threaded portions are tapered so filing off the bottoms of the transition piece wouldn't work, Looks like I'm in with a chance,here. The blue hylomar will fill the threads nicely and the locknut will steady the mixer.
 
I suppose that PTFE tape should take the temperature OK. It won't take exhaust gas temperature but presumably at this point it has water mixed with it, so the temperature is more reasonable. I was taught by my son that liquid PTFE is far superior to the tape, he was using it professionally for refrigeration/air conditioning construction and installation on super-yachts and said he had never had a leak with it. I have been using it for ten years now and agree. It will even seal Jabsco pump bayonet fittings when the O-ring is clapped out, something that I would have thought impossible.
 
Hi Vyv, I was hoping you'd come in on this. The problem is that the elbow is on the head, then comes the transition piece and finally the mixer. It's all subject to direct exhaust temperatures until the water is mixed with the exhaust in the bronze fitting. I'll e-mail you a photo.
 
I was going to suggest Loctite 55 which is a thread sealing string. It is superior to PTFE in that it can be "backed off" ie undone slightly for alignment purposes. The top temperature it will take is 130C. I guess the exhaust temperature at the seal point is higher than that. +1 for exhaust putty like Gun Gum then. It will be gas tight but hard to unscrew.
 
GUN GUM has been used by me in the past, but I prefer Hylomar. Neither is suitable on it's own in this case as i also need to screw the bits up tight (hence the question about thread tape). The current solution proposed is to use a new nipple (odd word but that's what a 1 1/2" BSP Male to male adaptor is called apparently) in DZR Brass screwed tightly into the elbow, using hylomar. The mixer will then be assembled on the proud thread, using hylomar and a locknut. Watch this space in two years to see if it's an improvement.

BTW the highest temperature tape I could find was for 280 degrees C.
 
Topcat47 said:
Hi Vyv, I was hoping you'd come in on this. The problem is that the elbow is on the head, then comes the transition piece and finally the mixer. It's all subject to direct exhaust temperatures until the water is mixed with the exhaust in the bronze fitting. I'll e-mail you a photo.
Click to expand...

May be useful if you posted the photo here. If it's on the non-wet part of the exhaust, Holt Firegum may help. It cures hard once heated (by the exhaust heat) and will not leak. May not be easy to remove again though.
 
Yngmar said:
May be useful if you posted the photo here. If it's on the non-wet part of the exhaust, Holt Firegum may help. It cures hard once heated (by the exhaust heat) and will not leak. May not be easy to remove again though.
Click to expand...

The OP sent me some photos. The connection is in the hot part of the exhaust before water injection point. I made a suggestion of a product that should take the temperature but he seems to have gone a different way.
 
vyv_cox said:
The OP sent me some photos. The connection is in the hot part of the exhaust before water injection point. I made a suggestion of a product that should take the temperature but he seems to have gone a different way.
Click to expand...

That's a most unusual course for a thread to follow. I don't know why the OP didn't simply go to your website and contact you by email. It would have saved us all some time perhaps!

Richard
 
I tried to post the photo here, but it didn't work. I sent the picture to Vyv in reply to his post.

The solution proposed by Vyv involved a high temperature thread adhesive like locktite but capable to 700 degrees C. I spoke to the supplier and he thought it was not suitable for my purposes, although in retrospect, I suppose it might have worked in conjunction with the locknut.

I have tried Firegum in the past, but the cured material eventually crushes under the shock/vibration/bending moment action to which the plot is subject.

I opened up the post to the forum in case others were suffering similar problems or had overcome them.

I am a retired chartered marine engineer. I have always found Vyv's posts informative and sensible and would not ignore his advice lightly. Indeed, I've reserved his suggestion in my armoury in case the method I"ve used doesn't work.

I also manageed to find a source of tape the would accept higher temperatures that PTFE thread tape. A boiler fitter tried to convince me to use Gas tape which is a bit thicker than ordinary thread tape but otherwise no different,
 
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