Anode Q.

[Yannis]

One of the 5 anodes in my Yanmar squirts water big time. Either it is not screwed deep enough, or has jumped a thread.
I tightened it and it now just drips. I called my mechanic and he said that I should rather put some teflon instead of tightening it up too much.
I said that with teflon it will stop making contact with the engine body; he says it's alright, anode protection is there despite of any contact.
Can anybody please confirm this? Thank you.

[Navatech]

Yannis,

First, if the anode is tightened and it "squirts water big time" you really need to pull it and see what's going on... Whatever it is, it needs to be taken care of!...

Second, for the anode to do its job (sacrifice itself), the anode HAS to have electrical contact with the rest of the engine... The general thought is Teflon (and other thread sealants) will insulate the anode housing thereby insulate the anode... However, unless there's a lot of sealant (and I do mean a LOT), the sealant will be crushed or pushed away and an electrical contact WILL be made... You can easily test for the existence of the electrical contact... Take a mulitmeter, set to ohms, touch the brass zinc nut with one probe and the engine block (bare metal) with the other... If your meter shows no resistance (0), you´re good to go...

[mike ohlstein]

If you must...... use a tiny bit of tape on the last two threads. But don't wrap, wrap, wrap the whole thing. Without metal to metal contact, you're wasting your time.

[Yannis]

Yeah, so I thought...I'll do exactly that, I'll pull it, clean the threads, put it back ....if it still drips I'll pull it again and wrap 2-3 layers of teflon tape at the last threads.
I'll also do the multimeter test.
Thank you guys.

[Tony Meola]

Just don't strip it. As my father you used to say, don't squeeze the eyeball out of it.

If you can get the right tap, meaning to match the threads, just in case you have a bad thread, you can run a tap up there to clean up the threads.

[Bill Fuller]

Which anode is giving you problems?
Is it the one of the ones on the end plate
or the one on the side, forward on the heat exchanger?

[Amberjack]

If you can get the right tap, meaning to match the threads, just in case you have a bad thread, you can run a tap up there to clean up the threads.

Tony--I have the same minor seeping issue with my Yanmar engine anodes and got the same technician advice--just use a little sealant. I bought a tap through for the threads but I'm concerned that might alter the original thread configuration. If the anode nuts are tapered to seal, are the female threads on the engine also tapered? Would running a tap through the engine threads change their configuration?

Bill--All of them seep a very minor amount but it's been 13 years so I guess they're entitled to a little leeway.

[Tony Meola]

Tony--I have the same minor seeping issue with my Yanmar engine anodes and got the same technician advice--just use a little sealant. I bought a tap through for the threads but I'm concerned that might alter the original thread configuration. If the anode nuts are tapered to seal, are the female threads on the engine also tapered? Would running a tap through the engine threads change their configuration?

Bill--All of them seep a very minor amount but it's been 13 years so I guess they're entitled to a little leeway.

Doug

I think Carl would be best to answer that question since he is the machinist on the board. Send him a PM just in case he does not see this. If the threads are not tapered then the tap should thread in real easy to start. Once it does that you should be good to go.

[Yannis]

Bill, its the one fwd left.
Anyway, I took it out, played "doctor" a little bit with a q tip trying to clean the threads without leaving any lint behind, put it back...still drips.
Pulled it again, wrapped 3 rounds of teflon tape around just the last threads, put it back, run engine up to 2000rpm, no leak.
Tested it with the multimeter as per Nav's instructions,reading says zero.
I think Murphy just stepped out of my boat to the next one, for a while.

[Carl]

Tony--I have the same minor seeping issue with my Yanmar engine anodes and got the same technician advice--just use a little sealant. I bought a tap through for the threads but I'm concerned that might alter the original thread configuration. If the anode nuts are tapered to seal, are the female threads on the engine also tapered? Would running a tap through the engine threads change their configuration?

Bill--All of them seep a very minor amount but it's been 13 years so I guess they're entitled to a little leeway.

Doug

I think Carl would be best to answer that question since he is the machinist on the board. Send him a PM just in case he does not see this. If the threads are not tapered then the tap should thread in real easy to start. Once it does that you should be good to go.

Short quick answer- clean out the threads best you can then install. If you want to use tap...avoid going deeper...just use tap to clean out any gunk and corrosion, AKA- Chasing the Thread.



The Longer, drawn out more then you want to know answer....


Anode Plug and the Threaded hole are both NPT threads, Nation Pipe Taper.

Both mating parts are angled (tapered). IF you want to clean female thread with tap "chase" you do not want to go further or deeper then already tapped as tap will cut away material, enlarge hole, making plug seat lower in hole. Not a huge problem unless plug bottoms out or locks on last imperfect threads...in both cases forget plug sealing well at that point. For reference, you should get 2-1/2 to 3 turns of thread engagement to point threads seats. Little more or less is fine.

IF you tapped hole through...in essence you would have an NPS thread...National Pipe Straight...it is a mechanical joint that is not meant to seal but hold piping together...You'll find this thread on conduit and lamps.



**** Now for the confusing part...

NPT threads are meant to seal with the use of a sealing compound, pipe dope, thread compound or tape. For an anode you want to use a conductive sealing compound. Tape "should" rip and tear when locking up and sealing so contact "should" be made.
Often the plug is soft enough to deform and seal without use of a sealing compound so often they are seen assembled dry and they will seal when snugged up.

****NPTF threads, National Pipe Taper Fuel...AKA- DrySeal threads, they ARE meant to be assembled dry and seal tight. Both male and female need to be NPTF to seal properly. I do not recall ever making anodes or anode plugs to NPTF spec...and I make tons of them every year.

I think at this point you know more then you wanted to know, if not I can go on...

[Charlie J]

when changing mine
I use to clean the threads with a small wire brush
then put a small amount of anti sieze on the male thread
when installing new zinc pencils

[Charlie J]

good info carl

[Bill Fuller]

Yannis
The forward zinc on the heat exchanger should be shorter than the others.
You should cut of about a 1/2 inch before installing. Otherwise it may be hitting the tubes.
I change my zincs about every 6 months and over 17 years and 5200+ hours I have never had any issues. No seeping ever.
I used to use a lubricant on the threads (Teflon tape or other), but any more I don't. Makes no difference.
Just snug them up nicely and you are good to go.
Bill

[IRGuy]

I am going out on a very shaky limb here but I will risk it. Mike O is correct.

As a chemical engineer who has spent a good bit of my career in chemical and power plant design, construction and maintenance, I have been responsible for overseeing and testing miles of pipe of various sizes and carrying everything from air to drinking water to concentrated sulfuric acid to molten sodium.

I was taught, and believe it to be true, that teflon tape and pipe dope in general are not in fact sealants. They are used as a thread lubricant to allow the installer to more easily tighten the joint and create sealing metal to metal contact between the pipe and fittings. In cases where the pressure is low the pipe dope might help in sealing a threaded connection, simply because it was present between the threads, but when you are dealing with hazardous chemicals and high pressures and temperatures the metal to metal contact is what provides the actual "mechanical" seal.

I will now step aside and let some of you challenge my explanation.

[Bill Fuller]

As a retired research chemist, also having dealt with lots of all types of chemicals and flows and some very high pressures,
I agree with your statement 100%
Whatever you put on the threads is there to allow the threads to mesh together smoothly (a lubricant).
And prevents galling.
And as Yannis found out experimentally, even with Teflon tape you still have complete metal to metal electrical contact.
Bill

[Yannis]

Guys, I believe you. Lucky teflon worked for me.
Bill, I buy the anodes from Yanmar, I dont cut anything, they are the right size in a little plastic bag all 6 of them.
Do you mean that I should reduce the length of the anode that yanmar sells to me?

[Bill Fuller]

Yannis,
Completely possible that Yanmar is providing you with shorter zincs than I am accustomed to finding.
I do use after market ones, and I can only find them in one length, which is a bit long for the fitting on the side of the heat exchanger.
Interestingly enough, most of the kits I find here only come with 5 zincs and seem to leave out that one on the side.
Just for curiosity, if you have one handy could you measure and post the length?
Glad the Teflon worked for you.
Bill

[Carl]

I am going out on a very shaky limb here but I will risk it. Mike O is correct.

As a chemical engineer who has spent a good bit of my career in chemical and power plant design, construction and maintenance, I have been responsible for overseeing and testing miles of pipe of various sizes and carrying everything from air to drinking water to concentrated sulfuric acid to molten sodium.

I was taught, and believe it to be true, that teflon tape and pipe dope in general are not in fact sealants. They are used as a thread lubricant to allow the installer to more easily tighten the joint and create sealing metal to metal contact between the pipe and fittings. In cases where the pressure is low the pipe dope might help in sealing a threaded connection, simply because it was present between the threads, but when you are dealing with hazardous chemicals and high pressures and temperatures the metal to metal contact is what provides the actual "mechanical" seal.

I will now step aside and let some of you challenge my explanation.

Shaky limb aside...

What seals is not in my book of knowledge.

What I can say and stand behind is every NPTF, National Pipe Tapered Fuel will meet NPT standards but an NPT thread may or may not pass NPTF standards. NPTF are dry seal threads meaning they will seal tight without the aid of a lubricant or sealants by metal to metal contact...although lubricants can be used. A thread designated as NTP can have imperfections on mating surfaces that are taken up by the aid of a sealing compound and usually only used in low pressure applications.

I rarely make NPTF threads in Bronze, Brass, Zinc or 303SS. I do make tons of NPTF fittings in 316SS and Monel.


What is my guess...Our Brass or Bronze plugs are soft enough to easily deform and seal without the need for a sealing compounds.

What is also my understanding the sealing compound is forced into the imperfect gaps of mating NPT threads.



I do not design or test...I just make and verify fits to gauges. And like most of us assemble stuff on boats and home plumbing...

[Yannis]

Bill,

I cannot take out that anode because I just put it in with all that hassle associated...unfortunately I also do not seem to be able to find some spare ones I think I had onboard...out of recent memory though this particular one appeared to be around 5 cm long (the lead part). I hope this helps.

[Bill Fuller]

Yannis,
No problem, just curious. I usually just buy mine from local suppliers and there is only one length
available. Years ago I could get shorter ones locally. Looking on the internet, I see you can get almost any length you want.
When you mentioned you had just the one seeping, I thought you might be bottoming out on the fitting on the side of the heat exchanger.
Have a nice summer.
Things are starting to really get going here in San Diego. I have already managed to put 225 hours on my boat this year.
Bill

[IRGuy]

Carl...
I never realized there were 2 tapered pipe thread systems.

Just when I begin to think I know it all...
Somebody like you comes along and teaches me something

Thanks!

[Tony Meola]

So that settles it.

Like Frank I never realized two types of threads existed. I thought there was only one type of tapered thread. Also, a big AND, Carl has settled the issue of tape or no tape. Tape it or use dope, its made to allow metal to metal contact.

But Carl, one question, how do you know if the dope is conductive or not?

[mike ohlstein]

Try this...

[Carl]

Like Frank I never realized two types of threads existed. I thought there was only one type of tapered thread.

Actually there are more then NPT and NPTF tapered threads. There is the overseas version, the BSPT, British Standard Pipe Thread and Metric Tapered Threads and Hydraulic tapered and....

But Carl, one question, how do you know if the dope is conductive or not?

Now this one took my by surprise...I have been under the impression there were a bunch of products out there that are thread sealant or joint compounds that were electrically conductive. I have never actually looked for one...today I did.

I found products that conduct electricity that lubricate, epoxies and adhesives that are conductive...but manufacturer said too thick for sealing threads.

I called Loctite (Henkel), spoke with their applications engineers and they said they had nothing they would recommend. They did know of some clients that used antisieze compounds that were conductive...but did not seal well in all circumstances. They had some clients that used their thread sealants and in making joints very tight were able to make continuity. But overall had nothing they would recommend.

So I then spoke with tech at company we make Anodes and Anode Plugs for. They sell to everyone including DOD... I inquired about sealing NPT threads. Answer was being clean NPT usually seal fine in low pressure applications; anything requiring sealing they recommend design using O-ring for sealing. When I asked about a joint compound or tape to aid in sealing NPT threads, they said it could hamper conductivity and would not recommend. I pushed further to find out what their clients used, but was told they only verify parts are to NPT spec.

Last but not least I called a buddy/customer that runs service for a fleet of Pilot boats. His company sent him for training on corrosion, sacrificial anodes, galvanic isolators. First he said all the new applications the anodes come across with O-rings to seal. On the older items with NPT plugs install dry is preferred. If they leak...clean mating parts then try to fit dry. If they still leak, he will use a liquid teflon and then verify by Ohming to mating part. If he still has a leaking problem the last choice is tape wrapped high, then ohming to verify conductivity.

[Tony Meola]

Carl

That is great info. In fact, I bet no one has ever tried to really get to the bottom of this question. So in actuality, the safe and definitive way is to design it with an O ring.

I have never used tape or dope and never had a problem. Now watch what happens when I change it this year.

If it leaks it's Yannis's fault.

[Yannis]

Tony,
You can blame it on me, but first, I cannot claim that I understand anything from this tapering alternatives jargon,or, how It could ever be useful to me ...lol....I cannot become a machinist or anything like Carl, now or ever !

Then, to be honest, I'd rather the anode didn't leak in the first place, so I could have more time to spend with those pink elephants !
And please, if it doesn't leak already, don't touch it !

[Tony Meola]

Yannis

Blaming it on you is a joke of sorts. After all have to blame it on someone other than me and since you brought this problem to all of us and now that Carl researched and settled this problem, well there is only one person to blame, the originator of the thread. LOL.

[Navatech]

And please, if it doesn't leak already, don't touch it !

We're talking anodes here... They're sacrificial... If you don't "touch" them you end up "touching" a whole lot more!...

[Carl]

I have never used tape or dope and never had a problem. Now watch what happens when I change it this year.

Now ain't that the truth...and I do not mean isn't.

If it leaks it's Yannis's fault.

Works for me, thanks Tony! LOL

[Rawleigh]

"Actually there are more then NPT and NPTF tapered threads. There is the overseas version, the BSPT, British Standard Pipe Thread and Metric Tapered Threads and Hydraulic tapered and...."

Oh, yes! The JCB nightmare hydraulic fittings!!!