Reply
 
Thread Tools Search this Thread Display Modes
 
Old 10-26-2019, 11:25 PM   #1
Member
 
Santana's Avatar
 
City: CHATSWORTH
Country: United States
Join Date: Dec 2018
Posts: 7
Heat Exchanger Patch

Hi Trawler Forum,

I have a Sen-Dure heat exchanger for a FL120 that was purchased as a backup. The heat exchanger on the motor is damaged and I want to replace it with the backup. The backup is pressure tested and looks good. I will replace the anode with a new Zinc and plug. I should have left well enough alone but I backed out one of the two drain plugs on the unit. I am pretty sure it is the raw water side but have not confirmed that. The drain plug did NOT come out clean.

So my question is: Can I use JB weld or Marine Tex to seal it back in? Or should I tap out the drain plug areas and install a new plug(s) - I don't know if the thread is NPT or a straight thread and I do not know how to tap an NPT I think the material is bronze but I am not 100% sure about that... It could equally be made out of brass, I don't know. Also, I could have the radiator shop that pressure tested it weld them shut and mark with a permanent marker "Do Not Remove" --

What would you all do? Outside of getting a new one. This one looks good, it tested properly, and I already own it.

Thank you for your help!
__________________
Advertisement

Santana is offline   Reply With Quote
Old 10-27-2019, 01:06 AM   #2
Guru
 
City: Clearwater, FL
Country: United States
Vessel Name: Seas the Bay
Vessel Model: 1981 42' Hardin Europa
Join Date: Aug 2016
Posts: 624
What do you mean by, did not come out clean? Damaged threads on the heat exchanger?

There's nothing special about NPT threads. They can be chased or tapped like any other. Just need the right taps.

If it is beyond chasing, any reason not to drill it larger and tap it for one size larger plug? Unless it mechanically barely a fit as is, should be room. Doubt it is too cramped, unless others have been here before.
__________________

gkesden is offline   Reply With Quote
Old 10-27-2019, 02:26 AM   #3
Member
 
Santana's Avatar
 
City: CHATSWORTH
Country: United States
Join Date: Dec 2018
Posts: 7
Thank you gkesden,

Yes, that is what happened, the male plug end threads sheared off inside the tapped hole. I thought as much that it might be okay to tap the hole and install another plug. As long as I am doing one I should do both so the drain outlets can be used for their intended purpose. There is certainly enough room to tap it out. The only question is what metal the existing plugs are made from. Thanks for your response.
Santana is offline   Reply With Quote
Old 10-27-2019, 08:40 AM   #4
Veteran Member
 
City: Baltimore, Maryland
Country: USA
Vessel Name: HAVEN
Vessel Model: Golden Star 35
Join Date: Jul 2013
Posts: 57
Heat Exchanger Patch

I had the same problem 2 years ago. The threads on the pencil zinc were slightly shredded. I bought a thread "chaser" tap and with extreme caution, "cleaned up" the exchanger body threaded hole. I used some thread cutting oil, turning the tap a 1/4" at a time while trying to ensure nothing dropped in to the hole. When done I replaced the zinc with thread sealant. So far, 2 years later, it has worked for me.
artfulltune is offline   Reply With Quote
Old 10-27-2019, 10:27 AM   #5
Member
 
City: Poway
Country: United States
Join Date: Aug 2019
Posts: 10
While NPT threads aren't 'special', they are unique in that it's a tapered thread. Pipe taps are made to create this taper, how far you drive it in determines the size of the thread, and how far the mating part installs, so watch your depth. You may find yourself tapping, installing, removing, tapping more, etc... Not rocket science, just annoying. Go slow and Good luck!
Kirwan is offline   Reply With Quote
Old 10-27-2019, 10:53 AM   #6
Guru
 
City: Clearwater, FL
Country: United States
Vessel Name: Seas the Bay
Vessel Model: 1981 42' Hardin Europa
Join Date: Aug 2016
Posts: 624
If the problem is that some of the male threads are broken off and stuck, rather than female threads being broken, you might try to "chase" the threads. And, by that I mean slowly and carefully tapping them the same size to clean them out and clean them up, rather than cutting new ones. If it doesn't work, you can drill, go up a size, and cut new ones.

What is the heat exchanger made of? Unless it is something weird, being on the raw water side, I'd expect the plugs to be bronze. It could be cupronickel, but even on exchangers made of cupronickel, I think they often opt for softer bronze plugs. And, well, since they broke...

You can probably just call Sen-Dure and ask what the plugs are made of. And, if you can just chase the threads, they can probably sell you new ones.
gkesden is offline   Reply With Quote
Old 10-27-2019, 12:11 PM   #7
Guru
 
Xsbank's Avatar
 
City: Pender Harbour, BC
Country: Canada
Vessel Name: Gwaii Haanas
Vessel Model: Custom Aluminum 52
Join Date: Sep 2013
Posts: 3,240
Silver solder a ball valve for drainage.
__________________
Don't believe everything that you think.
What are we offended about today?
Xsbank is offline   Reply With Quote
Old 10-27-2019, 03:59 PM   #8
Senior Member
 
Island Cessna's Avatar
 
Join Date: Feb 2011
Posts: 130
Quote:
Originally Posted by Santana View Post
Thank you gkesden,



Yes, that is what happened, the male plug end threads sheared off inside the tapped hole. I thought as much that it might be okay to tap the hole and install another plug. As long as I am doing one I should do both so the drain outlets can be used for their intended purpose. There is certainly enough room to tap it out. The only question is what metal the existing plugs are made from. Thanks for your response.


I would expect a good outcome from chasing the threads with an NPT tap. The taper should help getting the tap started. Be sure to get the tap engaged properly in the old female threads so you cut out the remnants of the plug, not the body of the heat exchanger. Work the tap back and forth once it is well engaged in the female threads, the old plug thread material will probably come out in chunks and you want to let them clear.
Island Cessna is offline   Reply With Quote
Old 10-27-2019, 04:03 PM   #9
Guru
 
Russell Clifton's Avatar
 
City: Anacortes Wa.
Country: usa
Vessel Name: Sea Fever
Vessel Model: Defever 49 RPH
Join Date: Sep 2012
Posts: 589
Sounds like part of the drain plug is still in the exchanger? If so, will it leak if left as is? You could use some epoxy putty to seal it off. No big deal not having a drain plug, just remove the cap on the end of the heat exchanger and it will drain.
Russell Clifton is online now   Reply With Quote
Old 10-27-2019, 04:35 PM   #10
Guru
 
City: gulf coast
Country: pinellas
Join Date: Jun 2014
Posts: 2,798
Can you pick out the male thread pieces with a dental pick? I have found them useful for similar work.
bayview is offline   Reply With Quote
Old 10-27-2019, 04:58 PM   #11
Guru
 
City: Boston
Country: US
Vessel Name: Adelante
Vessel Model: IG 30
Join Date: Nov 2016
Posts: 645
Heat exchangers and coolers are typically made of copper but many are copper nickel for better corrosion resistance. Plugs are typically brass as are the fittings soldered to the main housing. As others have mentioned, recutting the threads is easiest approach. If you use the same dia tap the bottom threads may be useless. If you have 6 good threads left you may be OK. Just coat the drain plug with some sealant and don't over snug it.

My fittings have a tube right under the drain plug and I believe they are 5/16-28. I would need a bottom tap. Check yours with a thread gauge.

Note that drain plugs are merely a convenience. You can drain the exchangers by pulling the hoses off.
SoWhat is offline   Reply With Quote
Old 10-27-2019, 09:28 PM   #12
Guru
 
Maerin's Avatar
 
City: East Coast
Country: USA
Vessel Name: M/V Maerin
Vessel Model: Solo 4303
Join Date: Jun 2013
Posts: 825
You should have no trouble chasing the threads with a NPT tap. Chase the threads, work the tap back & forth, your objective is to sort of polish the thread surfaces. Blow out the debris with compressed air, or use a wire brush to remove any leftover burrs. Clean the mating surfaces with brake cleaner, then re-install the drain plugs. I'd use LeakLock or other dope on the threads, you can use a good grade of heavy teflon tape and dope on top of that if the fit is a bit loose. The tapered thread can be chased pretty deep and still seal up OK.
__________________
Steve Sipe
Selene 4303 Maerin
http://maerin.net
Maerin is offline   Reply With Quote
Old 10-28-2019, 02:50 AM   #13
Member
 
Santana's Avatar
 
City: CHATSWORTH
Country: United States
Join Date: Dec 2018
Posts: 7
Thank you, everyone, All great answers, and suggestions. I will let you know how I get on. It is a fine thread 32 thread pitch or a metric 1 fine thread pitch. I might have that terminology off but hopefully, my explanation is enough to explain the approximate size. So to use the correct tap, this is info I need. I put a call in and I hope to get an answer. The dental pick is a good idea to potentially clear it out... it is soft metal. I am going to hit it hard tomorrow and hopefully be done quickly and accurately with no leaks!!

Thanks!!!
Santana is offline   Reply With Quote
Old 11-01-2019, 10:43 AM   #14
Member
 
City: Poway
Country: United States
Join Date: Aug 2019
Posts: 10
Quote:
Originally Posted by Santana View Post
Thank you, everyone, All great answers, and suggestions. I will let you know how I get on. It is a fine thread 32 thread pitch or a metric 1 fine thread pitch. I might have that terminology off but hopefully, my explanation is enough to explain the approximate size. So to use the correct tap, this is info I need. I put a call in and I hope to get an answer. The dental pick is a good idea to potentially clear it out... it is soft metal. I am going to hit it hard tomorrow and hopefully be done quickly and accurately with no leaks!!

Thanks!!!
You may have fixed it by now, but those numbers don't sound right. 32 threads per inch is pretty fine, NPT threads are much coarser. Also, 1mm would be 25 threads per inch. I don't know metric pipe fittings, but here's a quick chart of NPT (inch) sizes. Note- Pipe threads are specified by the ID of the pipe, and the actual diameter of the fitting is much larger.
One trick to determine the size is to go through your drill bits and find the largest one that will fit through the tapped hole; this will be close to the 'tap drill' listed.
Attached Images
 
Kirwan is offline   Reply With Quote
Old 11-06-2019, 12:38 PM   #15
Member
 
Santana's Avatar
 
City: CHATSWORTH
Country: United States
Join Date: Dec 2018
Posts: 7
Quote:
Originally Posted by Kirwan View Post
You may have fixed it by now, but those numbers don't sound right. 32 threads per inch is pretty fine, NPT threads are much coarser. Also, 1mm would be 25 threads per inch. I don't know metric pipe fittings, but here's a quick chart of NPT (inch) sizes. Note- Pipe threads are specified by the ID of the pipe, and the actual diameter of the fitting is much larger.
One trick to determine the size is to go through your drill bits and find the largest one that will fit through the tapped hole; this will be close to the 'tap drill' listed.
Thank you! Yes fixed installing today - have two new gaskets, o-rings and anode pencil. I hope it all goes okay.

And yes the chart is correct it is NPT 1/8" with a 27 thread. Took me a little time to figure all that out.
Santana is offline   Reply With Quote
Old 11-06-2019, 12:45 PM   #16
Enigma
 
RT Firefly's Avatar
 
City: Slicker?
Country: Bumpkin?
Join Date: Oct 2007
Posts: 12,740
Greetings,
Don't you all agree that if the US subcribed to SI measurements (metric), life would be a LOT simpler? 27 TPI. What engineer came up with THAT?



__________________
RTF
RT Firefly is online now   Reply With Quote
Old 11-06-2019, 02:21 PM   #17
Guru
 
Russell Clifton's Avatar
 
City: Anacortes Wa.
Country: usa
Vessel Name: Sea Fever
Vessel Model: Defever 49 RPH
Join Date: Sep 2012
Posts: 589
This past summer after changing the anodes in my Sp135's, I decided to remove the drain plug on the oil cooler (not sure why I decided that). As soon as I turned it, the boss the drain plug is tapped into just crumbled. I wasn't in port so I plugged it up with some epoxy putty and cruised that way the rest of the season. Yesterday i replaced the cooler with a new one from American Diesel. It was the starboard engine so that cooler is on the outboard side of the engine. I was really dreading the job but was pleasantly supersized it went so smooth. Had it changed in about 30 minutes.
Russell Clifton is online now   Reply With Quote
Old 11-06-2019, 02:22 PM   #18
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,685
Quote:
Originally Posted by RT Firefly View Post
Greetings,
Don't you all agree that if the US subcribed to SI measurements (metric), life would be a LOT simpler? 27 TPI. What engineer came up with THAT?

a full description of any NPT thread will fill this page! A lot of ROW doesn't know how to properly tighten an NPT fitting. With good reason, there is no torque spec.
diver dave is online now   Reply With Quote
Old 11-11-2019, 05:36 PM   #19
Guru
 
jimisbell's Avatar
 
City: Ingleside-On-The-Bay, Texas
Country: USA
Vessel Name: Papillon
Vessel Model: 1978 Mainship 34 Trawler #95
Join Date: Jan 2018
Posts: 612
Quote:
Originally Posted by RT Firefly View Post
Greetings,
Don't you all agree that if the US subcribed to SI measurements (metric), life would be a LOT simpler? 27 TPI. What engineer came up with THAT?




Personally I think if Europe would switch to our measurements that would ALSO work. Personally I think its stupid that 24mm is not exactly an inch. Who came up with that weird measurement??? The math to deal with partial mm takes much longer.
jimisbell is offline   Reply With Quote
Old 11-11-2019, 07:12 PM   #20
Senior Member
 
Soo-Valley's Avatar
 
City: Gulf Islands
Country: canada
Vessel Name: Soo Valley
Vessel Model: Grand Banks 36
Join Date: Jul 2019
Posts: 179
Quote:
Originally Posted by jimisbell View Post
Personally I think if Europe would switch to our measurements that would ALSO work. Personally I think its stupid that 24mm is not exactly an inch. Who came up with that weird measurement??? The math to deal with partial mm takes much longer.
I grew up with imperial and had to learn metric.
That said math is based on 10, metric is based on 10, so who decided to make imperial based on 12?
__________________

Soo-Valley is online now   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 05:34 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×