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Author Topic: Heat Exchanger Zinc  (Read 5024 times)

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Brad Young

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Heat Exchanger Zinc
« on: March 22, 2011, 11:24:39 AM »

Did something pretty stupid this weekend. I wanted to replace the zinc in Heat Exchanger. I could not get the old one out. Well I got out the breaker bar. Then I broke the nipple or flange that the zinc screws into. I did not realize that there was a place to put an opposing wrench. So, the damage is done and is fixed.

I think there was a small drip when I put the since in 6 months ago, so I tighten it up pretty good.

I now want to put in a new zinc. Can I put Teflon tape / copper or Teflon washer on the zinc?
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Brad Young
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Kevin Henderson

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Re: Heat Exchanger Zinc
« Reply #1 on: March 22, 2011, 11:52:16 AM »

Brad,  I just went through the changeout of my HX Zinc as well... although without the difficulty that you went through.  As I understand it you cannot or should not use any Teflon tape between the the threads of the Zinc and the HX.  Full metal to metal contact is necessary for the Zinc to work.  I'm certain others will voice their more seasoned insight into the matter than me but to my knowledge.. no Teflon tape.
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Ron Hill

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Re: Heat Exchanger Zinc
« Reply #2 on: March 22, 2011, 02:34:38 PM »

Brad : You need thread to thread contact so you are "electrically" connected.  Use Teflon tape and you could isolate the Zn and then the copper in the HX would arrode instead of the Zn!!

Clean the threads both male and female with a battery terminal tool.  Then see if it will install with out a leak.  If you still have a leak, my advice is to use antiseize on the threads, the copper antiseize would be the best.  That is a tapered pipe thread so no washer will work.   A few thoughts
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Bob K

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Re: Heat Exchanger Zinc
« Reply #3 on: March 22, 2011, 06:25:33 PM »

Brad,
A trick I learned (by accident) to remove a stuck heat exchanger zinc is to run and warm up the engine first. 
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Bob K
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Tom Clay

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Re: Heat Exchanger Zinc
« Reply #4 on: March 22, 2011, 10:24:13 PM »

A difference of opinion.... When my boat was delievered new it had teflon tape on the zn. I have used teflon tape for the last 5 years, and never had any leaks. I check the zn every 3-4 months and usually 50% or more is gone so I replace it, it's apparently making a solid connection. In talking to different mechanics it appears they are split on this issue, some use it and some don't.
« Last Edit: March 22, 2011, 10:30:48 PM by Tom Clay »
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Ted Pounds

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Re: Heat Exchanger Zinc
« Reply #5 on: March 23, 2011, 08:00:35 AM »

I would guess that as long as some of the threads are exposed (not covered w/ teflon tape) that you would have a good enough electrical connection for the Zinc to do its job...
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Ted Pounds
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Bob K

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Re: Heat Exchanger Zinc
« Reply #6 on: March 23, 2011, 05:09:33 PM »

Teflon tape tears very easily  - if you wrap it tightly you can see the threads will cut right through it as you wrap.  So you are still making metal to metal contact. If no contact  the zinc would not corrode.  Having said that, I'd still opt for a conductive sealant like Ron suggested.
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Bob K
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Indian Falls

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Re: Heat Exchanger Zinc
« Reply #7 on: March 24, 2011, 04:24:46 AM »

Here's my advice after 30 years of working in fittings: Since it is a tapered pipe thread you can leave the Teflon tape off the first 2-3 threads where it will make more than adequate contact with the HX fitting. 3 wraps of Teflon on the remaining threads will seal if the threads old or new are prone to leak.  Even if you put Teflon on all the threads it is pretty unlikely that running the plug into a taper with a wrench will not obliterate the Teflon on the first thread.  Chance of isolation is pretty small but possible, say, if you screw it in with your fingers only.

If it leaks after this, remove, clean it off, and apply a few more wraps of Teflon tape in the same manner as before.  This only has to hold water for a year or 6 months, so tighten just enough or you'll wear out the permanent part prematurely.  If it leaks and you crank it in more you're just trying to make up for lack of sealant by ramming it in.  This is a maintenance thread, not a permanent threaded connection, so don't use the old addage that you don't use sealant because tapered threads self seal. True, but if you do you'll need a new bushing on you HX in short order.



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Dan & Dar
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Ralph Masters

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Re: Heat Exchanger Zinc
« Reply #8 on: March 24, 2011, 08:06:06 AM »

Teflon tape is a lubericant for the threads to assist in obtaining a leak proof seal, not a sealing tape.  Joint sealing compound is ment to seal.

Ralph
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Ralph Masters
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Indian Falls

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Re: Heat Exchanger Zinc
« Reply #9 on: March 24, 2011, 12:42:01 PM »

Ralph is correct, but again that is for connections that are meant to stay together for awhile. 
Teflon tape is used to seal between almost all threaded plumbing fittings, whether it be copper, brass, plastic or steel pipe thread.  Brass to brass sort of self lubricates and "usually" no sealant/lubricant is needed there.  Pipe dope contains Teflon or other lubricant as well as the sticky goey petroleum base it's made from.

Tef tape is my choice for a maintenance thread like the zinc plug.  Stick with the tef tape, it's clean and easy if nothing else and still stops leaks in spite of it being a lubricant.  Always make sure you wind it on clockwise when viewing it from the zinc end or it will shred and pile up as it goes in. 
This is not a mandate just some friendly advise.  Over and out.
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Dan & Dar
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SeaFever

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Re: Heat Exchanger Zinc
« Reply #10 on: March 26, 2011, 10:54:54 AM »

Guys, it has been said before. The Teflon tape is an electrical insulator and can prevent the electrical connection between the zinc and the HE.

What is the primary purpose of the Zn? To save the engine parts from corroding due to electrolysis. Yes, the secondary, albeit important, purpose is to keep the water leaking from the HE. So keeping the primary purpose in mind, I would avoid any possibility of an impaired electrical connection.

It has also been said that Zn plug has a pipe thread hence it will bite into the HE and make its water tight seal. Yes, it will then also bite into the Teflon and make an effort to make the electrical contact but why oh why would we make it any difficult for it to get the electrical connection? If the water is leaking, there is a reason why it is. Find the reason and fix it.

My two cents...
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prh77

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Re: Heat Exchanger Zinc
« Reply #11 on: March 26, 2011, 04:49:16 PM »

If you have ever taken apart a fitting sealed with teflon tape, you will note that most of it is missing from the threads. I think the nature of pipe threads strip most of it away. If it stops the leak, I think you will still have plenty of metal to metal contact. Just a thought or 2 cents or whatever.
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Ron Hill

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Re: Heat Exchanger Zinc
« Reply #12 on: March 26, 2011, 05:39:41 PM »

Guys : FACT -- The contact between the threaded plug on the Zn, temperature sender/switch and the oil pressure switch/sender is the ground electrical connection necessary for those items to function properly!!

Just do what ever you please.   Stu's saying --- Your boat Your choice   Out !!   :rolling
« Last Edit: March 27, 2011, 05:35:40 PM by Ron Hill »
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Stu Jackson

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Re: Heat Exchanger Zinc
« Reply #13 on: March 26, 2011, 09:29:06 PM »

...most of it is missing from the threads. I think the nature of pipe threads strip most of it awayI..still have plenty of metal to metal contact.

Reality check, please.

Most?  Usually just the top of the threads, which means, at BEST, only 1/3 connectivity.

Would you deliberately do that kind of connection on your electrical system?

Yup, your boat, your choice.
« Last Edit: March 27, 2011, 05:08:03 AM by Stu Jackson »
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Brad Young

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Re: Heat Exchanger Zinc
« Reply #14 on: March 31, 2011, 09:47:47 PM »

Here is what happened.

Got the nipple welded back in. Cleaned threads with a battery terminal brush. Put in the zinc, it did not leak.  :clap
I did not have to add Teflon or Anti-Sieze.

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Brad Young
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