Fusible plug removal

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Fusible plug removal

Post  Tim Watson on Mon 24 Oct 2016, 9:02 am

I generally like to take out the fusible plug every year to check it, and also to know that if it were dropped, then it could be removed reasonably easy in extremis. Last year the plug was removed, but the head was badly affected in the process. The plug is always replaced with PTFE tape on it. This year, the plug would not be removed and, in the end, it needed drilling out! Steve has had similar problems with removing his plug recently.

I have subsequently re-tapped (cleaned) the plug hole with a 3/8 BSP second tap and have stocked up with a couple of 3/8 BSPT(tapered) plugs from LSM. These have a 3/8" square head, the same as a socket set drive. (I used a similar plug very effectively on my previous engine).

Anyone else had any problems with removing the STW parallel thread fusible plug?

Tim
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Re: Fusible plug removal

Post  lynnr on Mon 24 Oct 2016, 10:20 am

Humm.

My inspector requires the plug removed every year for visual inspection of the plug for partial melting and the boss for thread wear or undercutting.
I put tape on mine and also a smear of copper slip. Never have a problem removing and the head is still sharp and true.
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Re: Fusible plug removal

Post  Tim Watson on Mon 24 Oct 2016, 10:37 am

Forgot to mention that I also put on copper grease. I wonder if it's a function of how far in the plug goes to pull up tight. Mine was right in to the head.

Tim
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Re: Fusible plug removal

Post  LiveSteam on Mon 24 Oct 2016, 7:46 pm

Likewise, with my inspector, plug always has to be out and cleaned, last year we replaced it due to some waste'age (think thats what its called)

I've stopped using PTFE tape on pretty much everything now and just use copperslip, I've seen some discussion somewhere that PFTE tape has a nasty habit of actually damaging the threads as it clogs them up and can flattern, stretch them as the tape doesnt really have much compression. So far no sign of any problems and since I've stopped using it I think my bungs and plugs come out easier.

One thing to remember is PTFE tape isnt really a sealer but a assembly lubricant and copperslip seems to do just as good a job.

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Re: Fusible plug removal

Post  sonick45 on Mon 24 Oct 2016, 8:40 pm

LiveSteam wrote:Likewise, with my inspector, plug always has to be out and cleaned, last year we replaced it due to some waste'age (think thats what its called)

I've stopped using PTFE tape on pretty much everything now and just use copperslip, I've seen some discussion somewhere that PFTE tape has a nasty habit of actually damaging the threads as it clogs them up and can flattern, stretch them as the tape doesnt really have much compression. So far no sign of any problems and since I've stopped using it I think my bungs and plugs come out easier.

One thing to remember is PTFE tape isnt really a sealer but a assembly lubricant and copperslip seems to do just as good a job.

I second what you say LiveSteam. Ive had issues with PTFE tape on steam fittings as its binds up the threads when your tightening up the fitting and slightly distorts the threads. you get a good seal but when you want to take the fitting apart you have problems. I've used copperslip or graphite paste ever since and havent had the same issues.
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Re: Fusible plug removal

Post  Steve Traill on Tue 25 Oct 2016, 10:29 am

I've just removed my fuse able plug, with some effort required! and when it was finally out the brass thread was left in the boiler.  The plug came out with no thread at all on it.  I use PTFE tape on pretty much everything including the agricultural engine and never had a problem and that has it's plug removed every year.  My thoughts are perhaps there are different grades of brass being used here.  I know that some of the spanish brass plumbing fittings are really crap and only last a couple of years before corroding away.  Is it a bad batch of fuseable plugs that were made?  When I've cleaned the thread up I'll try the copper slip approach.  Not the easiest part to get at with a tap to clean the thread, planning to lift the front end up as high as I can so I can see what I'm doing.  Can't risk cross threading the tap!!  A tapered plug might be the answer, will have to look into that one.
Finally when the plug was out about a third of the solder had wasted away so I'd had a close shave somewhere!
Definitely needs looking at on a regular basis.
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Re: Fusible plug removal

Post  lynnr on Tue 25 Oct 2016, 12:34 pm

Btw. Mine is still as new. Wink
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Re: Fusible plug removal

Post  LiveSteam on Wed 26 Oct 2016, 6:37 pm

Mine looked like the orginal last year when we changed it which made it 10yrs old, still servicable and will be kept as a spare Very Happy

It had only wasted by a few mm but we felt it was safer replacing it anyway.

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