I've been studying the large number of Canadian engines with top mounted check valves--in which both injector lines run to a single opening on the top of the boiler. I've always heard that this provided "better water circulation" than our traditional U.S. side mounted check valves. Can someone explain enough here to help understand the concept and why it's important. I've heard of one steam operator who is rebuilding a 1904 engine who plans to change the check valve location because it is "so much better."
Jim

http://nctrans.org
Wrinnbo@aol.com

> I've been studying the large number of
> Canadian engines with top mounted check
> valves--in which both injector lines run to
> a single opening on the top of the boiler.
> I've always heard that this provided
> "better water circulation" than
> our traditional U.S. side mounted check
> valves. Can someone explain enough here to
> help understand the concept and why it's
> important. I've heard of one steam operator
> who is rebuilding a 1904 engine who plans to
> change the check valve location because it
> is "so much better."
> Jim not quite what it does is prevent cold water from hiting the side sheets. when the water enters the boiler the steam brings it up to full boiler temp. thus avoiding thermal shock on side sheets. the last nyc 4-8-2s built by lima had to have new side sheets after 12 to 18 months . they tried top checks and the side lasted until locos were cut up. ref. railway mech. eng . 1944 or 1945. if i have time i will try to find artical. thats all for now regards bb


staybolt2@netscape.net

Jim,
All of the Santa Fe big power had the top checks. Those would be the 2-10-4s, 4-8-4s and the 4-6-4s. The 3751 class was originally built with side checks but during the rebuild it was changed to top checks. One side of the feedwater had the hotwater heater entrance and the other from the injector. Both fed into a common T with cushion checks and a diverter. The diverter kept the incoming feed water from directly flowing onto the drypipe and causing somewhat of a cooling effect. The diverter also helped to somewhat spray the feedwater into the steam space in order to add more heat before it joined with the boiler water. I have been told and also read that side checked boilers tend to have the feedwater flow directly back to the firebox sidesheets. Another clue to what is probably happening is that top checked boilers tend to have mud build up at the front tube sheet while side checked boilers tend to build mud at the rear tube sheet.

The 3751 has yet to break any staybolt in any of the operations since 1990, and I know that there has been few. Boiler records in our possession show that this engine was very beneficial on the staybolts not breaking or replacing many even during shopping's.

Bob K

I don't know what's happening in the rest of the boiler, but when we looked closely at the barrel sheet under the check valves of our side-checked 2-8-4, after sandblasting we could see the track made by the cold feedwater downward along the boiler shell. There was no damage, just the indication that something was going on. Apexior coating will probably prevent whatever reaction is going on from affecting the sheet. I suspect that top-mounted checks are indeed better.

Aarne Frobom
The Steam Railroading Institute
P. O. Box 665
Owosso, MI 48867-0665

> I don't know what's happening in the rest of
> the boiler, but when we looked closely at
> the barrel sheet under the check valves of
> our side-checked 2-8-4, after sandblasting
> we could see the track made by the cold
> feedwater downward along the boiler shell.
> There was no damage, just the indication
> that something was going on. Apexior coating
> will probably prevent whatever reaction is
> going on from affecting the sheet. I suspect
> that top-mounted checks are indeed better.

> Aarne Frobom
> The Steam Railroading Institute
> P. O. Box 665
> Owosso, MI 48867-0665
I've had a little experience with low pressure stationary steam boilers and in one installation, feed water entered above the water level in the boiler. While it may have been easier on the boiler in terms of cold shock, the feed water flashing to steam on contact with the steam in the piping system caused an objectionable rattling in the piping system as the flashing to steam occurred. It sounded like fireworks going off inside the feedwater pipe adjacent to the point of entrance. How is this phenomena avoided on locomotives with top checks or is it?


jamesbane@hotmail.com

>Dear J.B.:
I believe that what you are refering to is "water hammering" caused by steam flowing into and mixing with the feed water in the feed water line due to a leaking check valve.
Both of our locomotives at the Valley have top checks (#97 came so equipped, we converted #40).
If you want an eye opening demonstration of how heat rises and cold falls, get yourself one of those hand held digital readout thermometers and "shoot" the water leg of your firebox and note the temperature. Now start the injector on that side of the locomotive and "shoot" the temperature several times over the course of a minute or so. You will see that even though the injected water is hot, it is cooler than the rest of the water in the boiler and therefore drops to the lowest point (the bottom of the firebox). The farther from the firebox that the feedwater is introduced, the better it is for the firebox.
J. David

jdconrad@snet.net

On the Cumbes & Toltec we had both top-mounted checks (on the 480's) and side-mounted checks (on 463, 497 & Rotary OY). We never had problems with sticking check valves on the top-mounted checks but did on occasion had troubles with the side mounted checks sticking.

I always figured that was because the side-mounted checks were under water all the time and scaled up much easier. The scale would cause them to hang up and stick open.

The Master Boilermaker's Association addressed and studied this issue several times, and reports exist in the minutes of their annual meetings, as well as reports published in Railway Mechanical Engineer in the late 1930's and in 1940.

Basically, the top mounted check, especially when equipped with a spray nozzel and/or a baffle plate under the inlet, was superior in every way to side-mounted checks. The top-mounted checks promoted circulation of the water and provided much less temperature differential. The incoming feedwater (whether from an injector or a feedwater heater), by passing through the steam space, was heated further and became much closer to the temperature of the water already in the boiler. That helped elminate or ameliorate cold spots.

Also, with the spray nozzels or baffles, the incoming water was broken up and dispersed better.

Tests showed that water coming in through side checks, being usually 150-225 degrees colder than the water already in the boiler, would sink to the bottom of the boiler and the firebox legs and lie there, unless the locomotive was working hard at the time. Thus, on a standing or drifting locomotive, this cold water would cause unequal expansion and contraction, which leads to cracks, in the firebox side sheets and even in shell courses.

Note that locomotives spent most of their time in those days (as diesels do today) standing still.

The proof of the pudding is that most new locomotives built after this information became known in the industry had top checks, as did virtually all locomotives rebuilt after the info became known. The exceptions were railroads that didn't believe it, or simply were too stubborn to change. A few railroads took a cheap but somewhat effective approach by installing an upturned elbow extension on the side check inlet inside the boiler. This directed the incoming water upward, allowing it to mix more completely with the water in the boiler. It wasn't as effective as the top check, but it was much better than the side check alone.

Where there ever studies done of the Pennsy practice of having the feedwater enter through a one way valve in the bachead and travel via a pipe over the firebox and dump out near the front tube sheet? It seems that traveling that distance inside the boiler would have to bring the temerature up substantially while letting it out in the coldest part of the boiler.

Did any other lines/builders use this practice?

Roger

Belpaire@aol.com

> Where there ever studies done of the Pennsy
> practice of having the feedwater enter
> through a one way valve in the bachead and
> travel via a pipe over the firebox and dump
> out near the front tube sheet? It seems that
> traveling that distance inside the boiler
> would have to bring the temerature up
> substantially while letting it out in the
> coldest part of the boiler.

> Did any other lines/builders use this
> practice?

> Roger dear roger it was not to bad an idea. however the pipe could plug up with scale and also brake off then it put the coldest water right at the worst place possible. i guss that is why the pennse was known for back that failed. regards bb


staybolt2@netscape.net

> Where there ever studies done of the Pennsy
> practice of having the feedwater enter
> through a one way valve in the bachead and
> travel via a pipe over the firebox and dump
> out near the front tube sheet? It seems that
> traveling that distance inside the boiler
> would have to bring the temerature up
> substantially while letting it out in the
> coldest part of the boiler.

Back in 1981 when I was at U.S.Navy Nuclear Power School in Orlando, Florida, I did the calculations as part of a heat transfer and fluid flow question with one of the instructors. I don't remember the exact answer, but I firmly remember that I was not at all impressed with the answer. It looks good until you do the math.

> Did any other lines/builders use this
> practice?

> Roger


nwstaybolt@reachone.com

> I've been studying the large number of
> Canadian engines with top mounted check
> valves--in which both injector lines run to
> a single opening on the top of the boiler.
> I've always heard that this provided
> "better water circulation" than
> our traditional U.S. side mounted check
> valves. Can someone explain enough here to
> help understand the concept and why it's
> important. I've heard of one steam operator
> who is rebuilding a 1904 engine who plans to
> change the check valve location because it
> is "so much better."
> JiM

Northern Pacific used top mounted boiler checks on much of its larger power. SP&S 700 has a top mount check with a deflector going over the dry pipe to both avoid direct contact of the cooler water with the dry pipe and to further heat it in the steam space before it adds to the boiler level. It is placed forward in the boiler.


http://www.montanarailtours.com
johnpcox@juno.com

According to the Worthington SA Tech Manuals I have, another desirable feature to the top feed vs the side feed is that the oygen-laden feed gives up its dissolved O2 directly to the steam. This oxygen therefore spends much less time in the boiler doing damage before it is carried out.

billbondie@ironhorsewater.com

I haven't seen one of these up close, but the pictures I have show a small valve on the top check valve which, of course, the side check valves don't have. I assume it would be used to open/shut the water feed but why would it be needed?

Thanks.

Jason

I have a couple questions regarding research that has been done on the top checks.

First, the Boilermaker Associations Meeting minutes... where can they be found on this particular topic online? I have read a .PDF from another of their topics (washout cool-down) and the subject was also referenced in their dialogue from a previous meeting.

Second, about what time were the check valves tried on the top of the barrel? The K-36 class engines that run on the D&S and C&TS were built in 1925 with top checks, yet a WP&Y 70 class and 190 class built in 1938 and 1943 respectively both feature side checks. This seems to me a little late in steam building years to feature side checks given the advantages mentioned. Considering all the above class engines were built by Baldwin, would this have been an individual railroad decision?

Third, if a deflector plate or nozzle was needed to keep the new water from hitting the dry pipe, depending on the size of the boiler couldn't this be avoided alternately by placing the pipe off center or is there not enough space when factoring in the amount of area that the water will dissipate once it exits the nozzle?

Last, the side checks with a 90 degree elbow on the interior of the boiler would likely have some issues with scale. Are there currently any engines being operated that practice this? What results have you found?

Pictures would be a big bonus too!

Thanks again.