Fusible Plugs

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Rowland
Posts: 110
Joined: Thu Jan 16, 2003 1:13 am

Fusible Plugs

Post by Rowland »

In the past, I have read where there are several folks that use fusible plugs as a matter of course. I ran across a series of articles that some of you may find interesting.

Regards,
Rowland


What is a Fusible Plug and How Does it Work?
http://www.steamtraction.com/archive/5424/

Fusible Plug Analysis
http://www.steamtraction.com/archive/5425/

The Medina plug
http://www.steamtraction.com/archive/5431/

A Short History of the Fusible Plug
http://www.steamtraction.com/archive/5509/

How Much Do You Know About Your Fusible Plug?
http://www.steamtraction.com/archive/5510/
bcody
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Joined: Wed Oct 29, 2003 12:07 am

FUSEABLE PLUGS

Post by bcody »

I'm going to stir the pot. I think their use should be MANDATORY on any boiler fired with solid fuel. With oil or propane firing the fire can be extinguished in an instant by closing a valve. This cannot be said of coal firing, there is a significant time lag between the decision to drop the fire and its actual dropping. Bill
sncf141r
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Joined: Mon Jan 06, 2003 10:06 am
Location: Canada

Post by sncf141r »

Bill;

As someone licensed to fire/drive the full sized locomotives, and as a live steamer, I'd disagree.

IMHO, on a live steamer, the best way of handling a low water
situation is to:

1) stop.
2) turn off blower.
3) cover stack with something, and,
4) get away from the locomotive.

Just let the thing cool down. With the thermal transfer rate through steel or copper, and water sloshing about, our low pressures, and the safety factor of boilers, I think this is the best way.


John Stewart.
User avatar
cbrew
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Location: Vancouver Wa

Re: FUSEABLE PLUGS

Post by cbrew »

Bill, Im going to chime in when my thoughts, (Don’t Laugh to Hard)
With any boiler operation, one should never be in a position that will mandate the need to drop the fire that fast.
One should ALWAYS know where the water is in the boiler at all times, regardless of the fuel being burned.
If you notice that the water pump or injectors have failed, you need to stop and shutdown all unnecessary steam consumptions and fix the issue, and if the issue can not be fixed, there is more then enough time to drop the fire.
Remember the water level will not drop if there is no steam consumption (aside from the normal shrinkage as the water starts to cool)

Another way to look at it, if the operator is not watching the water, regardless of the fuel you are going to have issues,
so it I had to choose,
I would vote to have Fusible Plugs in all fired boilers.

Another side note,
I do think a fusible plug would be any good in a boiler with siphon tubes or
Nicholson thermic siphons.

Anyways, I need to get back to work


bcody wrote:I'm going to stir the pot. I think their use should be MANDATORY on any boiler fired with solid fuel. With oil or propane firing the fire can be extinguished in an instant by closing a valve. This cannot be said of coal firing, there is a significant time lag between the decision to drop the fire and its actual dropping. Bill
If it is not live steam. its not worth it.
bcody
Posts: 954
Joined: Wed Oct 29, 2003 12:07 am

FUSEABLE PLUGS

Post by bcody »

John Stewart: What you propose will work from a safety point of view but you could lose a boiler. If you open the blower valve after you cover the stack you could get backfeed from the blower steam and douse the fire. Something to think about. BTW - I'm licensed by the State of Nevada to operate boilers, a license I received after attending a formal training class (Junior college level) and testing.

CBrew: You are baseing you your remarks on a qualified boiler operator. That is not always the case. It is usually the barely qualifed boiler operator that get themselves in a situration where the boiler water level is low and could cause an explosion. As safety is paramount, we must design, build and operate our equipment to offset the difficiencies of the barely qualified and keep our hobby safe. Just think of the brew-ha-ha we would have if someone allowed a boiler to explode at a meet. We would have state intervention in our daily activites to the point it would possibly kill the hobby.

I personally feel coal firing of our miniature engines is dangerous but there are many engines being fired by coal and safely operated by qualified engineers. What we must guard against is the dangers presented by the barely qualified. Remember what happen not too long ago when an unqualified man tried to run a steam tractor and blew it up. Don't want a repeat of that with one of our locomotives. The hobby can't afford it. Bill
Bill Shields

Medina

Post by Bill Shields »

the problem in Medina had nothing to do with how it was fired, it had to do with an idiot at the controls of a boiler that shouldn't have been used to heat a cup of tea....

Granted, you can snuff a gas or oil fire quickly, but you can also snuff a coal fire very past by stuffing the stack AND opening the blower...coal won't burn in a steam environment with no oxygen...and it goes out more than fast enough.

I have gotten frostbite from a propane fill line (idiot at the controls), seen a propane leak in a turntable area set a bunch of things on fire (NOT MINE!) and observed fuel oil running on the track from a leaking tender / feed line to the loco...making the track too slippery to run on....so every source of combustable fuel has its potential problems.

Anything can happen and we all need to be very careful, no matter what the heat source.

The one thing none of us need to feed is lawyers...
bcody
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Joined: Wed Oct 29, 2003 12:07 am

FUSEABLE PLUGS

Post by bcody »

The above comments just reinforce my position. We must design, build and operate our equipment in the safest way possible to make allowances for the individuals that are not up to speed when it comes to SAFETY. Bill
Rowland
Posts: 110
Joined: Thu Jan 16, 2003 1:13 am

Post by Rowland »

Some additional notes taken from a long post done by Kelly Lynch of Strasburg regarding fusible plugs. He mentions the boiler explosion in Medina, Ohio.

Follows an excerpt from that article:

Many of the historical references are interesting in their own right. For example, “... in 1978, Frank D. Graham, in Power Plant Engineers' Guide, ... concludes that fusible plugs are overrated. "They are unreliable," Graham states, "sometimes blowing out when there is no apparent cause and sometimes remaining intact when the plates become overheated."

Here is another historical quote, echoing many of the posts on this site of late, ‘James H. Maggard, author of The Traction Engine, Its Use and Abuse (date of publication unknown, but clearly early 20th century), takes something of a psychological approach in his criticism of the use of the plugs: "I would have no objection to the safety plug if the engineer did not know it was there. I am aware that some states require that all engines be fitted with a fusible plug. I do not question their good intentions, but I do question their good judgment. It seems that they are granting a license to carelessness."’

What brought me up for air was the revelation that while low water caused the traction engine explosion in Medina, OH in 2001 the fusible plug HAD NOT MELTED!!

This failure most likely occurred due to a lack of sufficient water in this area to insulate the already structurally weakened stay bolts and sheet and over firing." The report goes on to say that, "Apparent over firing and failure to maintain an adequate, constant water level" was a critical factor in the explosion.

As for the fusible plug, the Medina County Sheriff's report clearly states the fusible plug did not melt. In Section 2 of the report, an Aug. 10, 2001 letter from Dean Jagger, chief boiler inspector for the state of Ohio, to Lt. John Detchon of the Medina County Sheriff's Office states simply: "Fusible plug was still intact; the center had not melted out."’

Bruce goes on to say that while the tin used in fusible plugs melts at 450 degrees, over time it can transform into oxide of tin, with a melting point of 2,966 degrees. Previous studies have found that this transformation can take place after as few as 500 hours of service. The false sense of security caused by this transformation could be the cause of future accidents.
highiron999
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Location: Los Angeles, CA.

Post by highiron999 »

Rowland;

Now that was well stated. Thanks

Leonard Evans/highiron999
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Dick_Morris
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Post by Dick_Morris »

We must design, build and operate our equipment in the safest way possible to make allowances for the individuals that are not up to speed when it comes to SAFETY.
In my opinion, this philosophy would be a good argument for banning all 1-1/2" scale equipment - steam or otherwise.

That's not to say that there shouldn't be standards, just that both the risks and means to mitigate them need to be balanced. Personally, I'm a fan of a common set of standards for boiler design and construction, based on more than a half century of experience with our models. (That covers the time when 1-1/2" scale has been in common use.) Catastrophic failure of boilers isn't part of that experience, so mandatory use of fusible plugs wouldn't have prevented any failures.

A discussion on whether the use of fusible plugs would prevent a boiler from being extensively damaged would be more reasonable. Discussions on couplers, safety chains, signals, brakes, and operating qualifications for anyone operating equipment near the public would address the types of mishaps that have actually happened and will continue to happen at tracks where the aren't confronted.

The Medina boiler failure's main relevance to our scales is the public, political, and insurance companies' perception of the risks of the hobby. It's also a reminder that operating full-sized equipment while ignoring 100 years of experience relevant to that scale can make things go terribly wrong.
mrb37211
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Location: Nashville, TN, USA

Post by mrb37211 »

Safety chains...

More and more clubs are requiring safety chains, yet many cars, tenders, and locos anchor the chains with bent loop eye bolts. I've heard of several cases where the stress of a derailment or other happening straightened the eye bolt, allowing the units to seperate. I've also heard of a few cases where cars of wooden construction have been disassembled by the chains during an event.

If safety chains are to be required, shouldn't they be required to be sturdy enough in materials and mounting to fulfil the intended function of keeping the train intact?

Charles
chameleonrob
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Location: crude works

Post by chameleonrob »

Rowland wrote:

What brought me up for air was the revelation that while low water caused the traction engine explosion in Medina, OH in 2001 the fusible plug HAD NOT MELTED!!
If I remember rightly the required safety valve didn't work either.

Just remember that you can't make anything idiot proof.

rob
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