Steam & Excursion > Managing Standard Stokers, care & feeding...

Here's my experience with Standard stokers....

I first met the operation of stokers on George Hart's Rail Tours Inc, excursions on the Ma & Pa RR at York, PA., in 1965&66.
My stern coach and mentor, Ben Kantner, forbade young volunteers in the cab of steamers, once the fire was lit...

Why?
The inevitable distraction of the person in charge of the fire & boiler management...with crowds in the cab, to Ben, were an invitation to trouble.....
Ben insisted on the sole focus of the hostler being the management of the boiler, the water and the smoothe pressure-increase during fire-ups.

With cold water, Ben wanted the boiler to warm up slowly, over time --- he hated the popping and creaking of a straining boiler under too rapid a fire-up process.
The bigger the firebox, the greater the amount of sheet expansion. With the tubes under cold water, and anchored at the smokebox end, the furnace( firebox,
when 'forced', applies of heat to the crownsheet.... the crown tries to expand under the intense heat of the coal flames.

HOWEVER, the firebox, and crown, are anchored at the rear by the backhead and the rear of the mudring. So, under the influence of the high heat, the crown sheet expands forward, meeting the solidly-held rear tube sheet.....the joint at the front of the crown and the top of the rear tube sheet is commonly called
the "knuckle", The knuckle relieves the expanded crown sheet, by slightly rolling forward, over the tubes, and bending the top of the tube sheet.
Constant flexing of the knuckle, over time, leads to metal fatigue at that joint, cracking and weakening the knuckle and sheets at that joining seam, all the way across.

Constant variations of fire temperature and, thus, boiler temperature( as reflected in the boiler pressure gauge ) leads to the constant "expansion --contraction"
stresses on all the firebox components. With large, modern power, the best firing practices concern the controlling of the temperature excursions, by the cab crew, over the time that they have control over the boiler.

One night, after an excursion, over the Wild Mary, I was unexpectedly promoted to fireman on Hart's ex-CP 1286, a 250-psi boilered, stoker-fired, 4-6-2,
of small size, and immense capacity.

At Hart's operation, I had been allowed to get the firebeds built, cold, ---- but never to fire them, or to be in the cab, while fired... ( up to that point) .... so, that night, while waiting for a PRR diesel to haul us from the WM yard to the Ma & Pa yard, in downtown York, I was supposed to keep a calm, but ready fire....

At first I ran the stoker engine, and coal was delivered to the firing table.... the M&P engineer was 'Granny' Dunlap, --- so called because of his old-woman attitude and cranky demeanor and grumpy behavior.....

Soon, I had a huge mound of green coal, and a cold fire that was almost out! Granny mumbled about me using the shovel, and quit with the stoker..
Since I had never been instructed on basics of stoker operation, I was in deep trouble.... Granny DID give me a hint about the stoker jets..and I soon learned from there. I pushed the mound forward, but still the fire was bright, all the rest of the night, no more coal was needed...
[There are limits to cab-safety awareness, but Ben's rules set me up for, not good outcomes..].

I vowed to learn all about stokers and stoker management and design, from then on...
So, with that out of the way, here's what I would stress about successful managing stoker operations..

There are two styles of stoker designs that are most common: the Standad MB ( modified-B stoker) and the Standard HT stokers.
The MB uses a ' firing pot ' for delivering coal to the firebox, it is a large tube, with flex joints connecting the tender coal hopper to the locos firing table.
The HT stoker has an angled elevator tube, up through the cab floor, and uses an elongated firedoor opening in the rear, door sheet, In the HT, the elevator screw delivers the coal above, to a 'shelf', called the firing table. There are raised vanes in the table designed to channel the stoker jet streams ---deflecting the coal around the firebox. The best variant is the HT, and its competitors, when it comes to giving the best coal distribution.

In both types, the coal is moved through the stoker tube by a stoker-engine. The engine is a small, 2-cylinder motor that drives the gearing at the rear of the stoker trough ( about the middle of the tender) . Except for the entry into the fireboxes, the jointed, Archimedes-screw delivery system is virtually the same.
Modern stoker engine locations varied, but all accomplished the same thing. Later variants often mounted the screw driving engine in the tender, where it's conventional location is under the cab, beneath the fireman's seat.

The NKP 759 was fitted with a 5-jet, MB stoker, and it worked wonderfully, ----- once the NKP-boys showed us how to manage it...what follows is a condensation of that common knowledge. The stoker is NOT automatic, it must be managed and used appropriately, with good judgement and diligent monitoring.
While sitting around, the best practice is to hand fire the fire bed, casually,----- the stoker tends to flood a low-demand fire with more coal than can be properly burned. Good coal placement technique with the scoop, is more important than quantity delivered, per scoopful.

The rear of the stoker trough has a single-reduction gear box that turns the stoker screw, powered by the stoker motor. The drive shaft spins faster than the screw shaft, thus there is great 'mechanical advantage'.

DANGER !!! In case of sudden blockage in the stoker trough, the operating stoker engine may try to force the screw to turn.....
There's a shear-pin at the hub of the driven-gear ( in the trough gear-box), similar in purpose to shear pins for common boat screw propellers to the shaft attachments. In case of severe shock and breakage, the shear pin in the stoker screw shaft will shear, and the stoker engine will freely spin...
The only thing to do now is to grab the shovel...

In case of a sheared pin, ( abuse of the stoker....this must be prevented) , the rear gearbox cover plate can be accessed from under the middle of the tender...
There's a a flat cover plate over the two gears in the gear box....typically the gear box is packed with too much grease, and that must be dug out , to gain access the the hub of the large gear, and its removal to gain access to the screw shaft and its sheared pin.
The shear pin is probably locked in place by the. 'pin-smearing' action of the spinning gear over the frozen shaft.
Lots of luck, driving-out that shear-pin fragment!!!
I've never done it, never hpoe to do it...

The MB stoker screw is straight, with cardan joints , and ends at the base elbow of the elevator tube. Unlike the HT stoker, there is NO ELEVATOR SCREW.
The MB's straight screw, forces the coal up the tube, in a sausage like mass.
At the top of the tube is the firing table and the stoker jet casting, over the center of the tube opening.
The coal 'sausage' is blown around the firebox by the stoker jets. Typically, there are five sets of jets to the MB stokers.
However, on huge grate area locos, like Alleghenies, Big Boys , etc, they are fitted with stoker jet assemblies using 7- sets of separately controlled stoker jets.

The MB's firebox arrangement consists of the stoker elevator tube, rising ( typically 18" above the grate) in the firebox, protected by a row of vertical great bars arranged in a U-shaped, castle- like protector for the stoker tube. The top of the U-shaped rim is a casting called the firing table. The coal sausage is blasted away from the stoker tube and around the firebox. The stoker jet 'head' , being inside the firebox, has a couple of rear jets that aim the coal spray into the rear corners, very effectively.

Under heavy drafting conditions, the wind through the grates can lift and carry the 'fines' well forward in the fire box, so the wise fireman decreases the stoker
jet-pressure, so as to not end up with too much coal blown down, under the front of the brick-arch.

The MB also delivers its coal unevenly, the design of the stoker screw, winds up forcing most of the fines up the right side of the stoker tube to the jets, and larger lumps, often miss the full blast of the jets. The larger lumps, often land and remain at the rear of the grate area.
The fines, coming out if the right of the tube top, can if not watched, build up a big mound in the corner of the firebox, nearest the engineer...

When examining the condition of the firebed, DO NOT TRY TO LOOK IN THERE WHILE RUNNING THE STOKER.
You will not be able to see ANYTHING but white heat... it always amuses me when I see folks earnestly looking into the bright flame--- as if they can actually see anything!!! Wait for the gasses to all burn off then, examine your firebed.

You want to assess the condition of the firebed when the throttle is being closed-down or when the train stops.
Watch for mounds, where you don't want them and for bare areas, especially around the edges of the grate, where cold air rushes up the firebox sheets, and around the firing table...

You can use your shovel to sprinkle lumps of coal to cover bare spots. Use light scoop-fuels, rather than heavy, loaded scoops.
Placement is more important than quantity...
Also, use the shovel as a deflector, in front of the stoker jets, to blow coal into the rear corners.

NEVER fully turnoff the steam from flowing from the stoker jets.... you can partly close the stoker jets, but never stop the steam flow completely.
Fine coal particles can be forced into the jet holes, if no steam is blowing.... once lodged, the coal maybtry to burn, and the particles will expand, blocking the jet.
Solution: never totally turn-off the jets, another adbpvantsge to blowin jets is the cooling effect of the steam on the jet head and firing table..

If, however, you encounter a plugged stoker jet, try this remedy....
Identify the individual stoker jet control valve ( by your right knee), turn-off the steam supply and prepare to remove that one individual, valve bonnet, as an assembly.
With the valve handle and bonnet removed, it's OK to use your stoker jet (pointed) cleaning-tool to probe the plugged hole.....while probing the plugged hole, send a good amount of steam flow out the valve of the open bonnet....the steam stream will cause a Venturi jet vacuum at the end if the tube with the blockage,and will
suck the blocking particles out, into the wind.
ALWAYS CLEAR PEPLE OUT IF THE CAB, BEFORE DOING THIS OPERATION....

Next, when laying-up the stoker, whether for short time, or an extended period, ALWAYS BACK THE STOKER SCREW IN REVERSE.
To pull the 'coal sausage ' down, away from the firebox.... Drop the coal all the way to the bottom of the stoker tube, away from the fire.
If allowed to remain in the stoker tube, at the firebox, the coal at the top layer will try to burn; but, will instead, only partially burn and form a thick, solid mass of
smoldering coal and tar ....

DO NOT TRY TO USE THE STOKER EGNINE TO RAM THE SOLID CAKE UNDER AND INTO THE STOKER JET DISTRIBUTING HEAD.
You will endanger the stoker screw's shear pin, as above.

The evening before our first trip up Horse Shoe Curve, Harrisburg, PA., ( Sept 1970). one of our crew members was confronted with a solid coal mass at the top of the stoker trough...and he was VALIANTLY trying to bust it loose by ramming th stoker screw, full speed into the blocked sausage ...
Time after time, he slammed the spinning screw into the blockage..
Each time the screw rammed the stuck coal and suddenly stopped..

I was helping wash the tender sides, when the whole tender shook from the abuse...
Admittedly, I panicked, and screamed at the top of my lungs, to STOPPP!!
I absolutely LOST IT, in anger .... I was screaming and running towards the cab....( picturing the 'smeared' shear pin, -----,in all that grease-packed mess in the gear box. & .being up all night, with a drift pin, fighting to replace the ruined shear pin ...)

It was a shameful outburst by me, ...and it did prevent a broken stoker....buttt...it was still wrong way to behave, as a leader...
The only time I remember doing so...

So, those are the rules for the MB..treat it well, it will serve forever...

More on the HT, coming up...

W.

To 'proof' ,yet



Edited 10 time(s). Last edit at 06/27/17 03:20 by wcamp1472.

It's like Wes said.

-LD

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LarryDoyle..

Thanks MUCH...

W.


How'd you do over the weekend, with the scoop work?
A little sore today?
How well did the rebuilt loco perform?

wcamp1472 Wrote:
-------------------------------------------------------
[snip]
> How'd you do over the weekend, with the scoop
> work?
> A little sore today?
> How well did the rebuilt loco perform?

I won't hijack your thread (or, did you already hijack your own thread? If that's possible.), but a quick photo
essay appears here
https://www.trainorders.com/discussion/read.php?10,4323554

I'm putting together a trip report which may get posted tonite, or in the next day or so....

-LD

Thanks for the drawings..they make it easier on the explanation..

Hi-jacking is OK, by me...

Looking forward to your success...
Congratulations on a great restoration..

W.

And, now back to our regularly scheduled programming....

Referring to the advertisement drawings ...
Like all ads, these are deceptive and do not tell what actually happens in the firebox, under real conditions...

First, let's look at the lines representing the wind flow above the thin firebed .... the path up the rear of the door sheet, leads to the crown sheet, and represents the highest velocity air ant he firebox. The area under the brick arch, represents the slowest air path.

So, if the back area of the grates are bare, having no fire, the masses of cold air directly cools off the door sheet, the rear corners, and the crown sheet.
The greater wind velocity increases the burn-rate of the coal in that area..... thus, it burns bare very quickly...

The rest of the fire then gets fed more coal, trying to catch-up for the cold air effects....often yielding too much smokiness.
The disparate air flow worsens the problem of fluctuating firebox temperatures. So, now let's look at the make-upon the pieces, that make up the MB stoker.
Later I'll add in the lessons taught by the NKP-crews and also other 'Roads common experiences ...

As you can see in the profile of the firebox, the stoker tube is up inside the rear of the firebox, it is a support for the tube, and is surrounded by a base and U-shaped tower of cast iron grate components. Also the U shapted 'firing table' is slightly elevated, for cool air to circulate under the casting.. the immense volume of cold air vented through the supporting structure severely cools down the intended fire. And to make matters worse, the pressure differential, mentioned earlier, burns the corners to bare ....very quickly .

To counter the cold draft effects, the fireman MUST build the firebed to control and manage the firebed....
To manage the varying draft rates inherent in the physics of gas flow through the firebed.

So, it gets back to building the firebed to replicate the shape of the fireman's scoop.... as described in earlier posts...
Thus, the heavy bank in the rear, forces the major air flow through the thin, 'reduction' area of the flat firebed.

Thus, you get control of the cold air currents, and raise the internal firebox temperatures, as well as saving coal.

Also, in today's excursion trains, 100 sq ft grates are more than capable of operating the train ..... in fact, the actual ' load ' represented by excursion cars can be handled by 50-sq ft. grate area .... by wise, and constant 'heel' management at the back of the grates...

Using the heavy bank at the rear, a hot fire is easy to maintain , especially in down-hill periods, for keeping the air compressors snappy in making air fir the brakes..


W.

24 years later I would be #1286's regular week day fireman between Cumberland and Frostburg for the late Jack Showalter.... 2 trips a day 2 to 3 days a week.

I never had hand fire the #1286 up the mountain but we once had a stoker failure on her sister engine #1238 around Woodcock Hollow crossing. Luckily it was the 2nd. trip of the day and we only had 2 coaches but it was still a constant battle to keep her fed into Frostburg....

Tim Wilson

In 1967, Ross, High Iron Co, leased both the 1286 & 1238..

At that time the 1286 still had its Feedwater heater, etc.
The G5 class 4-6-2s were equipped with Standard HT-1 stokers---- a smaller version of the HT, they were about 80% the size of the HT components.... Perfect for modest size power, produced after the start of WW2, and later..

The '86 performed flawlessly.
Later in '67, Hart's crew rushed the 1238 into service for Ross. It had been parked since arriving from Canada, so Hart, Kantner and his crew did great job of returning her to service --- including the manufacture of all new poppet valves for the front end throttle!

But poor 1238 was never as reliable as 1286..... We had lots of problems, including a balky exhaust steam injector... Never seemed to work good.

Later in early 1968, We also leased Steamtown's
( Vermont) ex-CP 1278 for part of 1968. Like the '86,
The MS&N 127(8) ran like dream.... Real fast and flawlessly.

I'm glad to hear of your experiences..

Years ago, I visited with Jack, at his place in Virginia.
I was impressed with the work he had done on the two engines. Rollers on the tender trucks. 2 water glasses, etc.

He also had bought and moved the turntable from
Potomac Yards, AlexandriaVa.and a reconditioned, updated
( small) drop table, from PY.

I guess those two pieces still exist... They were BOTH in very good condition..... IIRC.
the turntable is 110-ft...

He was gentleman and it was a pleasure to meet with him, and his wonderful daughter, and I enjoyed the tour he gave for me & John Marino...

Thanks for your stories.

W.


Tim, send me a PM, if you can remember the reasons for the problem with the '38's stoker... Problem? Cause? Cure? Remedy? Preventing relapses? Etc..

For my upcoming write-up on the HT style Stokers..
TIA, Wes

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Edited 3 time(s). Last edit at 06/27/17 06:18 by wcamp1472.