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I was wondering, how does one work his/her way up to becoming a steam engineer.  Whether it's a tourist operation somewhere or one of the few that get to sit behind the throttle of one of the big horses like 611, 765, 844, etc etc.  What qualifications do you need, how does one starts out, do you need to have past experience with a RR, etc etc?  If some of the steam guys here could talk about how they got into engineers seat, that would be great.

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I can't speak from experience, since I've never been an engineer.  But about 20 years ago when I was unemployed, a Scranton, PA, college (darned if I can remember which one) was offering a two-year degree in steam engine technology.  I spoke to a recruiter about the curriculum, but never signed up, as it would have been too long a commute.  But I suppose that might be one way to get an in.

I recall reading that Cheri George (Fireman N&W 611J) got started by volunteering to wash the locomotives (1218/611) top-bottom-coupler-coupler. Based upon this, volunteering to do the most menial scutt-work is probably a good starting point. If you hope to be an engineer, being an engineer on a Class I Railroad and having a Class 1 Steam License would be a good start.

 

 That said, a "I'll do whatever it takes" attitude is almost certainly a prerequisite.  

 

And yes, I am an Engineer. But my world is controls and instrumentation aka "Little Sparks".

Last edited by Gilly@N&W
Originally Posted by Gilly@N&W:

I recall reading that Cheri George (Fireman N&W 611J) got started by volunteering to wash the locomotives (1218/611) top-bottom-coupler-coupler. Based upon this, volunteering to do the most menial scutt-work is probably a good starting point. If you hope to be an engineer, being an engineer on a Class I Railroad and having a Class 1 Steam License would be a good start.

 

No such thing as a "Steam License" in the railroad industry. One is either an FRA certified Engineer (Ticket to be correct), trained and certified by a specific railroad's training and certification process, or not. Rules compliance/knowledge is also part of the FRA Ticket.

 

 That said, a "I'll do whatever it takes" attitude is almost certainly a prerequisite.

 

A VERY good start, then learning the cause and effect of what REALLY is going on with a steam locomotive, then learning and qualifying at the Fireman's job. Finally "learning" the Engineer's job. Train handling is the toughest component. 

 

And yes, I am an Engineer. But my world is controls and instrumentation aka "Little Sparks".

 

I worked at an amusement park, (Knott's Berry Farm) as an Engineer/Fireman.  As Knott's is privately owned and the train operates on private property, it is NOT subject to FRA rules.  Simply was at the right place at the right time, with lots of enthusiasm and desire.  Started out being trained as a Fireman, then progressed through the internal training program to Engineer.  Mostly through OJT.  Knott's has 4 pieces of motive power.  2 Consolidations 2-8-0 engines from the D&RG, a Galloping Goose, and a small propane fired train for Camp Snoopy.  Was qualified on 3 of them, (1 Consolidation was undergoing overhaul during my time there.

On the new Hope Valley, we take all comers. You don't have to have steam experience--we have folks that can teach you. Of course, you'll move up the ladder more quickly if you have some understanding of steam locomotive operation. You will also have to have some physical abilities. There's a lot of heavy lifting involved with steam trains.

 

Generally, our guys start out at the bottom, as brakemen. You need to have some understanding of what happens on the ground to be a good engineer.

 

Eventually you might get invited into the cab to watch the fireman. You will participate in steaming up the engine, learning what that takes. You'll help fuel, water, oil and grease the engine. In the cab, under steam, the fireman will explain to you what he is doing and why he's doing it, while you watch. Later, you might get to fire while moving about the yard, with a qualified fireman behind you.

 

After many months of different firemen teaching you different techniques, you will be firing mostly on your own. The qualified fireman might only glance a few times at your pressure and water to make sure you're doing OK, and not instruct you as much. You'll be asked, "Are you ready to do one solo?" If you are unsure, you say so, and continue learning. If you're confident, you say so, and focus on what you need to do.  

 

On one trip, there will be a couple qualified engineers/firemen in the cab. Nothing unusual--there are often other cab riders. But unbeknownst to you, you're being tested. The won't tell you that you've passed, and are now a qualified fireman, until the trip is over--and you've performed to their satisfaction.

 

After a year or two of firing, you will have seen how the engineer does his job. You'll know about the throttle, brake, Johnson bar. You might get to operate the locomotive light in the yard. Moving back and forth, putting the engine into position. Again, a licensed engineer will be next to you the whole time.

 

Out on the line, depending on your engineer, you might be asked to operate the engine as it pulls the train. You'll learn to use the automatic brake valve while bailing off the independent, and how to hook up the Johnson bar.

 

Your training might continue in a diesel--which are easier to operate and learn on. Here you'll learn more about train handling, coupling, etc.

 

After you're demonstrated your abilities with both steam and diesel, you'll have a qualifying run with the DSLE (Designated Supervisor of Locomotive Engineers). If he signs off, you'll get an engineer's license.

 

So, that's pretty much it as far as one railroad goes.

Last edited by smd4
Originally Posted by Hot Water:
Originally Posted by Gilly@N&W:

 having a Class 1 Steam License would be a good start.

 

No such thing as a "Steam License" in the railroad industry.

 

I concur, but there is licensing for stationary boilers (NASOE). My point was having a through knowledge of boiler operations (even stationary) would be a good starting point.

Originally Posted by Gilly@N&W:
Originally Posted by Hot Water:
Originally Posted by Gilly@N&W:

 having a Class 1 Steam License would be a good start.

 

No such thing as a "Steam License" in the railroad industry.

 

I concur, but there is licensing for stationary boilers (NASOE). My point was having a through knowledge of boiler operations (even stationary) would be a good starting point.

Do you happen to know what size the boiler has to be these days to require a licensed operating engineer? Seems like size requirements have been getting larger over the years? I am retired (not as an engineer, but in a related trade), was just curious?

Last edited by rtr12
Originally Posted by Gilly@N&W:
Originally Posted by Hot Water:
Originally Posted by Gilly@N&W:

 having a Class 1 Steam License would be a good start.

 

No such thing as a "Steam License" in the railroad industry.

 

I concur, but there is licensing for stationary boilers (NASOE). My point was having a through knowledge of boiler operations (even stationary) would be a good starting point.

Possibly but, stationary boilers don't really have much in common with railroad steam locomotive boilers, with their constantly varying loads/steam demands. Plus, firing a locomotive boiler is mostly "by the seat of your pants" and all totally manual.

Originally Posted by Hot Water:
Originally Posted by overlandflyer:

you might consider the live steam hobby...

Operating live steam models is nothing like the "real railroad".

i don't recall saying it was... and if you can't deal with the added responsibilities, it's not a hobby you'd enjoy.  as a "real railroad" engineer i'm sure you've never had to deal with fuel shipments or even a fraction of the general maintenance involved with keeping a live steam model up and running.

 

regarding full scale engineering, i doubt if any sort of license or certificate would hold much weight other than perhaps identifying your competence to understand basic steam locomotive operation.  with any scale, steam locomotive a "type rating" would be essential.  with the few full scale steamers left in operation, i doubt if any two are close in performance.

 

steam on! ...gary

 

 

 

Originally Posted by overlandflyer:
Originally Posted by Hot Water:
Originally Posted by overlandflyer:

you might consider the live steam hobby...

Operating live steam models is nothing like the "real railroad".

i don't recall saying it was... and if you can't deal with the added responsibilities, it's not a hobby you'd enjoy.  as a "real railroad" engineer i'm sure you've never had to deal with fuel shipments or even a fraction of the general maintenance involved with keeping a live steam model up and running.

 

Well, you would be wrong in your assumption. Todays main line steam operations involve so much more that simply being a Fireman or Engineer. Taking on fuel, whether coal or oil, in a yard siding isn't simple as it sound, and water from any sure hydrant doesn't always go smoothly either. Then there is the constant inspections for loose/broken components, and lubricating everything that moves with the CORRECT lubricant, i.e. do NOT add valve oil to the air side of the air compressors.

 

regarding full scale engineering, i doubt if any sort of license or certificate would hold much weight other than perhaps identifying your competence to understand basic steam locomotive operation.  with any scale, steam locomotive a "type rating" would be essential.  with the few full scale steamers left in operation, i doubt if any two are close in performance.

 

steam on! ...gary

 

 

 

 

If you don't have a year to do all that, and/or don't really want to make a career out of it, try the Nevada Northern.  For something like $600, they will get you to the point where you actually operate a steam locomotive for several miles.

 

Live Steam models are like sailboats - you need to invest some time in the endeavor.  I thought i was just going to light a fire and go around the loop.  No way.

Originally Posted by Hot Water:
Originally Posted by overlandflyer:
Originally Posted by Hot Water:
Originally Posted by overlandflyer:

you might consider the live steam hobby...

Operating live steam models is nothing like the "real railroad".

i don't recall saying it was... and if you can't deal with the added responsibilities, it's not a hobby you'd enjoy.  as a "real railroad" engineer i'm sure you've never had to deal with fuel shipments or even a fraction of the general maintenance involved with keeping a live steam model up and running.

 

Well, you would be wrong in your assumption. Todays main line steam operations involve so much more that simply being a Fireman or Engineer. Taking on fuel, whether coal or oil, in a yard siding isn't simple as it sound, and water from any sure hydrant doesn't always go smoothly either. Then there is the constant inspections for loose/broken components, and lubricating everything that moves with the CORRECT lubricant, i.e. do NOT add valve oil to the air side of the air compressors.

 

...

 

unless you've been involved in large scale model live steam you're probably not going to get it.  these locomotives are built from castings and metal stock with the vast majority being scratch built.  there are no assembly instructions or operator manuals.  as an owner/ operator you are responsible for EVERY aspect of its operation and maintenance.  you take on coal at the yard?  how does it get there?  how many people does it take to support a full scale locomotive?  i'm sure it's more than one.

 

this past month i had to pull the pilot truck, change out the wheels and shim the axle which was a bit out of spec.  routinely i pull and clean the injectors.  every run day i punch the flues (ok, i only have 37, not 200+) and drop/ clean the grates, and yes, even with smaller scales, using the correct lubricants is essential to good operation.

 

other aspects?  i have a 14 car train i also maintain.  when running with engineer plus fireman duties being my prime focus, i enlist the help of a conductor to keep an eye on the train and passengers when that occurs, but offline there are air brakes, trucks and couplers that occasionally need work.

 

at a club level there is also the physical plant and track/ signal maintenance where its essential that everyone gets involved in a well run operation.

 

 

of course i'm sure being a full scale steam locomotive engineer would be an interesting diversion and at ~500x the mass of a 1:8 scale model i've got to believe there is a difference in the feel of operation, but at even 140 psi boiler pressure, a live steam model demands the same respect for safe operation.

 

i'm beginning to understand how Heinrich Dorfmann felt.

cheers...gary

Originally Posted by Gregg:

HW   do you  have  to deal with "clinkers" on the excursions. I suppose you can't just drop them any old place?

Considering that SP4449 is an oil burner, we don't get "clinkers". However, back in the American Freedom Train days, and operations through the early 1990s, we were still using heavier fuel oils (#5 and occasionally #6), since recycled waste oil had not yet become prevalent. With the heavier fuels, sometimes a "bone" of solidified carbon would develop on the floor of the firepan, in line with the burner. We would break that up with the long slash bar, and spread the pieces around on the floor of the firepan, and they would slowly burn up the next day. Really stubborn "bones" would require someone going in the firebox with a pick-ax to break-up the thing.

 

When I was involved with NKP 765, back in the late 1970s and early 1980s, the occasional clinker could be hooked out of the fire bed, and thrown out on the right-of-way. Sometimes a clinker can be broken up by squirting it with water from the Fireman's deck hose, and the instantaneous "cold shot" from the water, breaks up the clinker. 

Originally Posted by Hot Water:
Considering that SP4449 is an oil burner, we don't get "clinkers". However, back in the American Freedom Train days, and operations through the early 1990s, we were still using heavier fuel oils (#5 and occasionally #6), since recycled waste oil had not yet become prevalent. With the heavier fuels, sometimes a "bone" of solidified carbon would develop on the floor of the firepan, in line with the burner. We would break that up with the long slash bar, and spread the pieces around on the floor of the firepan, and they would slowly burn up the next day. Really stubborn "bones" would require someone going in the firebox with a pick-ax to break-up the thing.

We get that buildup on our rear firebox sheet. We call it a "carbon volcano" because of it's shape. I've often had to climb in to the firebox to try and chisel it away. That stuff is harder than cement! 

Originally Posted by overlandflyer:

you might consider the live steam hobby...

 

NKP753

where you typically need to simultaneously be engineer and fireman....

 

RLS-2014_103 13

and the public (we run in a city park) certainly enjoys live steam, too.

 

check out Pioneer Valley Live Steamers;

http://www.pvls.org/

 

should be in your area if your profile is correct.

cheers...gary

I read the whole thread here and it got me wondering if these ever blow up? What are the operating pressures? Do the pressures vary with each scratch built engine? I suppose they all have safety relief valves, but with them all being scratch built with no manuals or instructions steam can be very dangerous. What safety precautions do they take?

 

I have watched several youtube videos of these, both steam and gas powered (I believe those are all scratch built as well?) and they are all pretty fascinating. It does look like a lot of fun, running them that is. The building and laying track doesn't look nearly as appealing.

Originally Posted by rtr12:
Originally Posted by overlandflyer:

you might consider the live steam hobby...

 

 

where you typically need to simultaneously be engineer and fireman....

 

 

and the public (we run in a city park) certainly enjoys live steam, too.

 

check out Pioneer Valley Live Steamers;

http://www.pvls.org/

 

should be in your area if your profile is correct.

cheers...gary

I read the whole thread here and it got me wondering if these ever blow up?

 

I am aware of occasional failures, but never heard of a live steam model "blowing up".

 

What are the operating pressures?

 

The various inch and a half and 3 inch scale live steam locomotives I have worked on were generally 120psi to 160psi.

 

Do the pressures vary with each scratch built engine?

 

Apparently, yes.

 

I suppose they all have safety relief valves,

 

Safety valves on ALL steam locomotives are NOT designed to prevent them from "blowing up". The safety valve is for limiting maximum working boiler pressure in order to limit horse power for protecting the running gear machinery. No safety valve EVER prevented a full size steam locomotive from "blowing up".

 

but with them all being scratch built with no manuals or instructions steam can be very dangerous. What safety precautions do they take?

 

Keep proper water level in the boiler and don't burn your hands.

 

I have watched several youtube videos of these, both steam and gas powered (I believe those are all scratch built as well?) and they are all pretty fascinating. It does look like a lot of fun, running them that is. The building and laying track doesn't look nearly as appealing.

 

Originally Posted by smd4:
Originally Posted by Hot Water:
No safety valve EVER prevented a full size steam locomotive from "blowing up".

Well...except for that whole "Best Friend of Charleston" thing...

As I recall the story, the fireman became annoyed with the sound of the safety valve and put/hung something on it to close it. 

 

That was what we call today "operator error."

 

Rusty

Originally Posted by Wyhog:

No safety valve EVER prevented a full size steam locomotive from "blowing up".

I question that, Hot? Are you saying that if a loco had no safety valves it would still be impossible to fire it enough to exceed the boiler limits thus resulting in an explosion?

 

 

I didn't say that, and that is NOT what safety valves are for. As I stated, safety valves are essentially an audible warning device for the cab crew, i.e. Fireman and/or Engineer, that tells them that they are exceeding the max working boiler pressure. 

 

I find that hard to believe? I'd guess that safety valves prevented that kind of explosion many many times during the steam era.

 

Nope. Stop and think about how large the furnace system is on even an 1870s steam locomotive is. Do you really thing that little 2" diameter safety valve could prevent an explosion? Now take the N&W 611 for example; she has three 4" safety valves, a working boiler pressure of 300psi, and an enormous furnace system designed to evaporate HUGE quantities of steam per hour. There would be no way those three safety valves could even come close to preventing a boiler explosion if the crown sheet went bare.

 

I agree that safety valves are not going to have the capacity to prevent an explosion if the crown sheet became uncovered and then was flooded by a sudden upgrade change and flash boiled the water.

 

Well, there isn't much else that causes a steam locomotive boiler explosion.

 

But surely they must have prevented many boiler explosions that would have otherwise occurred due to dummy or inattentive firemen.

 

Nope, because a dummy Engineer that deliberately runs with "low water" is asking for an explosion, especially after topping a grade. Note, I say Engineer, since most railroads in the U.S. had the Engineer responsible for boiler water level, even in the modern era of big super power steam locomotives. The notable exceptions were the SP and UP, where the feed water controls were NOT accessible to the Engineer. There really isn't much a Fireman can do to cause an explosion, except stop putting water into the boiler, and safety valves will NOT prevent that either.

 

The whole design purpose of safety valves were/are to limit horse power to the running gear machinery. On high demand requirements, the Fireman can "fire against" open safety valves in oder to increase the working boiler pressure by maybe up to 5 additional psi, thus providing hotter steam through the superheaters and into the valves & cylinders for higher HP.

 

 

Thanks for the added info. My only experiences have been with stationary boilers and they are basically closed systems, unlike steam locomotives. Many years ago I read a couple of books about early stationary steam heating systems and blowing them up along with the buildings they were in was a common problem until safety devices began to be invented to help prevent the explosions.

Originally Posted by Hot Water:
Safety valves on ALL steam locomotives are NOT designed to prevent them from "blowing up"....The whole design purpose of safety valves were/are to limit horse power to the running gear machinery.

Hot, that's just not true. They're called "Safety" valves for a reason. If they were only to be used as an audible warning, there'd only be one.

 

Preventing boiler explosions was exactly what they were designed for "back in the day." They were used to relieve excessive boiler pressure as a means of preventing explosion. There are plenty of references in the literature. Two I have handy are Sinclaire and Kirkman--both from the early part of the last century. They may have been wrong in their thinking, but regardless, that was their sole purpose. Today, perhaps, we know differently.

 

So from the dawn of steam until as late as 1912, they were definitely NOT seen as "audible warnings." They were used to prevent explosions from overpressure.

Last edited by smd4
Originally Posted by smd4:
Originally Posted by Hot Water:
Safety valves on ALL steam locomotives are NOT designed to prevent them from "blowing up"....The whole design purpose of safety valves were/are to limit horse power to the running gear machinery.

Hot, that's just not true. They're called "Safety" valves for a reason. If they were only to be used as an audible warning, there'd only be one.

 

Preventing boiler explosions was exactly what they were designed for "back in the day." They were used to relieve excessive boiler pressure as a means of preventing explosion. There are plenty of references in the literature. Two I have handy are Sinclaire and Kirkman--both from the early part of the last century. They may have been wrong in their thinking, but regardless, that was their sole purpose. Today, perhaps, we know differently.

 

So from the dawn of steam until as late as 1912, they were definitely NOT seen as "audible warnings." They were used to prevent explosions from overpressure.

Then why didn't they prevent each and every boiler explosion over the past 150 years, whenever the idiot Engineer wanted to operate with low water for "hotter steam", and then topped the grade thus baring the crown sheet? 

Wouldn't it be fair to say that safety valves will prevent boiler failure due to excessive pressure?  I certainly agree that preventing boiler failure due to other reasons - such as low water - are of course not the job of the safety.  I don't presume to know FRA regs... all I can speak to is from a non-FRA boiler design perspective, where part of the process is to determine the amount of steam the boiler is capable of producing, then perform the calculations to make sure that the safety valves are capable of venting the necessary amount of steam without an excessive rise in boiler pressure past the set point of the primary safety.

 

Hot is correct that the set point of the safety valves (in PSI) is used to calculate the tractive effort of a steam locomotive, along with many other factors.

 

Anyway, from Grimshaw's "Locomotive Catechism", circa 1923:

 

 

 

LocoCatSafetyP164 [1024x791)

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  • LocoCatSafetyP164 (1024x791)

I contend that relief valves are there to prevent boiler failures under normal operating conditions.

 

A boiler is designed to withstand a given pressure. It is then subjected to a hydro-static test pressure to ensure that the design pressure can be met. The relief valve(s) is set to a safe working pressure, which is well below the design pressure.

 

Under normal and proper operating conditions, the relief valve prevents the internal pressure from even getting close to the design pressure, so therefore the boiler does not fail. Relief valves are sized to accommodate the maximum generation of steam by a given boiler when properly operated.

 

However, if an operating circumstance develops that compromises the design elements and therefore reduces the boiler's strength, the boiler may in fact rupture. This has nothing to do with the operation of the relief valve, which was not sized to accommodate a boiler weakened below the relief valve setting.

 

A dry crown sheet may be weakened by heat to the point it cannot withstand the maximum design boiler pressure as established by the relief valve. Or a steam flash incident may cause a pressure rise which exceeds the relief valve's capacity to vent the sudden and extreme production of steam, thus allowing the pressure to surpass the design strength of the boiler. Or a relief valve may in fact "stick" and allow the pressure to rise beyond the boiler design capability.

 

As previously stated, relief valves are provided in order to prevent boiler failure under normal and proper operating conditions.

 

 

 

 

Last edited by win86
Originally Posted by win86:

I contend that relief valves are there to prevent boiler failures under normal operating conditions.

 

A boiler is designed to withstand a given pressure. It is then subjected to a hydro-static test pressure to ensure that the design pressure can be met. The relief valve(s) is set to a safe working pressure, which is well below the design pressure.

 

Under normal and proper operating conditions, the relief valve prevents the internal pressure from even getting close to the design pressure, so therefore the boiler does not fail. Relief valves are sized to accommodate the maximum generation of steam by a given boiler when properly operated.

 

However, if an operating circumstance develops that compromises the design elements and therefore reduces the boiler's strength, the boiler may in fact rupture. This has nothing to do with the operation of the relief valve, which was not sized to accommodate a boiler weakened below the relief valve setting.

 

A dry crown sheet may be weakened by heat to the point it cannot withstand the maximum design boiler pressure as established by the relief valve. Or a steam flash incident may cause a pressure rise which exceeds the relief valve's capacity to vent the sudden and extreme production of steam, thus allowing the pressure to surpass the design strength of the boiler. Or a relief valve may in fact "stick" and allow the pressure to rise beyond the boiler design capability.

 

As previously stated, relief valves are provided in order to prevent boiler failure under normal and proper operating conditions. 

 

That may be fine for stationary boilers, but simply does not work for steam locomotive boilers.

Originally Posted by Hot Water:
Then why didn't they prevent each and every boiler explosion over the past 150 years, whenever the idiot Engineer wanted to operate with low water for "hotter steam", and then topped the grade thus baring the crown sheet? 

Hot, steam locomotives have been around since before 1941. Sorry to break it to you.

 

The folks before then had a different understanding of the physics and science of boiler explosions.

 

They thought overpressure caused a lot of boiler explosions. That's why they used safety valves. That's why they were invented. Maybe that's not how they're used today.

 

It's just a historic fact. Nothing personal.

Last edited by smd4
Originally Posted by Hot Water:

smd4,

 

What does 1941 have to do with it? There is no way that that little safety valve, even two, there or four of them, are EVER going to prevent a boiler explosion!

1941? Simple. You seem to be fixated on modern superpower, forgetting that there was a boatload of knowledge on the subject before the Daylight was built.

 

That knowledge may have occasionally been wrong. But the simple fact remains that safety valves were invented--and used for nearly 100 years--in an attempt to prevent boiler explosions due to overpressure. It's a historical fact (as noted above, in Grimshaw's seminal work), contrary to your assertions that the safety valve was invented to limit HP to prevent damage to machinery.

 

Your move.

 

Last edited by smd4

"That may be fine for stationary boilers, but simply does not work for steam locomotive boilers." -  Hot Water

 

Why not?

 

Are you suggesting that locomotive boilers are thrown together at the whim of the maker with whatever material is at hand with no consideration of their intended operating pressure, not hydro-statically tested, and have a relief valve of any diameter opening and containing some spring off of the shop floor screwed into the boiler?

 

I remain firm in saying that the information in my previous reply - and the information offered by WindupGuy -  applies to both stationary and propulsion boilers.

Last edited by win86

 

It seems to me that three pops would prevent, or discourage someone from deliberately over firing the engine just to get maybe 350 lbs out of a boiler designed for 300 lbs. All the extra work would just be vented to the atmosphere to discourage a practice that would surely have been tried by those needing, or wanting higher pressure for whatever reason. Even though the boiler would safely handle a small amount above and beyond what the pops are set at, it would create more wear and tear on everything. But there is just no way three pops will keep the boiler from exploding during the instantaneous pressure spike that occurs when relatively cold water hits a red hot crown sheet.

Originally Posted by locopilot750:

 But there is just no way three pops will keep the boiler from exploding during the instantaneous pressure spike that occurs when relatively cold water hits a red hot crown sheet.

That apparently doesn't happen. The Pennsy did an experiment where they sprayed cold water on a hot crown sheet, and nothing happened.

 

http://www.rypn.org/forums/vie...plosion&start=75

Last edited by smd4
Originally Posted by smd4:
Originally Posted by locopilot750:

 But there is just no way three pops will keep the boiler from exploding during the instantaneous pressure spike that occurs when relatively cold water hits a red hot crown sheet.

That apparently doesn't happen. The Pennsy did an experiment where they sprayed cold water on a hot crown sheet, and nothing happened.

 

http://www.rypn.org/forums/vie...plosion&start=75

So the crown sheet didn't rupture in the PRR "rest"? What about all the other catastrophic boiler explosions as a result of low water and a bare crown sheet? Multiple safety valves sure didn't help, did they?

Originally Posted by Hot Water:
So the crown sheet didn't rupture in the PRR "rest"? What about all the other catastrophic boiler explosions as a result of low water and a bare crown sheet? Multiple safety valves sure didn't help, did they?

I agree... safety valves are sized to relieve the Boiler Steam Generating Capacity (the term used in the FRA Form 4) under normal operating conditions.  A low water condition is very abnormal.  The safety valves are helpless to prevent a boiler explosion due to low water.

 

I'm surprised that no one has mentioned the safety device designed to prevent boiler explosions due to low water... the fusible plug.  It gives an audible and visual indication that something is wrong, as well as using steam to smother the fire during a low water event.  Very simple, very elegant...

I think some of you may be confusing what causes a boiler explosion.  Most of the boiler explosions I'm aware of are the result of a crown sheet failure due to being run dry; not from a failure of the crown sheet to withstand the boiler pressure.

Correct me if I'm wrong but I believe most modern boilers were built with a safety factor of 4 meaning a boiler with a working pressure of 250psi is theoretically capable of withstanding 1000psi...theoretical.  So if it was even possible to over fire a boiler to 50psi over its working pressure, the boiler should have no problem.

As I said earlier, the explosion results from a crown sheet failure.  When the crown sheet fails, it is due to metal fatigue from over heating.  The fire may not be hot enough to melt steel, but it is certainly hot enough to fatigue it.    Remember that at 250psi, water doesn't begin to boil until it reaches 407 degrees Fahrenheit.  When there is a crown sheet failure, you are now taking water/steam under pressure and exposing it to atmospheric pressure.  This can result it a volume expansion of up to 1700 times.  The rapid and sudden expansion in volume is the explosion.

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