Your steam pressure is WAY to high. To get the maximum heat from the steam you want it to condense in the radiator. At 150 psi your boiling point, at sea level, is 365 F. If a pound of steam passes through that radiator and cools 1 degree, you get 1 BTU per lb of steam. If that steam condenses to water, you get 972 BTU per lb. This due to the heat of vaporization of water. So your trainline should have just enough pressure to get it to each car without condensing. As it expands in the radiator you get MUCH more heat because it should codense there and give up the heat of vaporization.

For some reason, I had arrived at the understanding that the "trainline" ran at elevated pressure (and saturation temperature) to give adequate heat at necessary mass flow through to the last car's trainline.

I often saw pictures of the rear of the trainline at least partly open and venting steam, perhaps to encourage actual mass flow by enhancing a pressure differential. It would be hard to imagine, especially in the post-WWII world where even the mass flow of steam (from expensively-treated water) to blow whistles was sufficient to justify adoption of air horns, that any venting of actual steam beyond that needed to handle condensate would be adopted for very long... at least, until passenger-profitability rot had set in...

The high pressure in the trainline would then reduced down to 'vapor' pressure to be passed through the car radiators, where full condensation would occur (and the condensate be exhausted through traps with minimum steam loss).

Someone who has firsthand experience with steam-ejector equipment can state what the expected operation pressure was -- I believe it is in surviving documentation, but I don't remember what it is and am too ill to go search for it.

Keep in mind that developing mass flow from a boiler full of overcritical water at over 240psi saturation pressure is a very different thing from developing it from a flash boiler or steam generator using an oil-fired monotube with forced once-through circulation. The latter would benefit from high generator operating pressure; the former would likely be tapped from the turret (through the reducing valve that is part of the current set of questions).

I don't see any way you could heat over a couple of 'sequential'cars with low=pressure steam unless you had an enormous mass flow, through substantial diameter pipe, with remarkably good insulation. Even then, your first cars would likely be ovenlike and your last cars chilly...

I believe the necessary insulation to run reduced pressure through the trainline is actually available today (under the general name of 'nanoinsulation') although I don't know at what cost per car.

None of my training handbooks specify a train line steam pressure. They more or less state that it is up to the Conductor. I would guess that he would judge how much steam is exiting the rear end valve. Each car had a vapor heating regulating valve that controlled the inlet of the steam from the train line to the heating coils in the car, typically one psig or less. The valve was controlled by temperature of the exiting steam/condensate from the coils. At 212 degrees or more the inlet steam would be shutoff. Vapor heating was invented in the early 1900's according to John H. White's book The American Railroad Passenger Car.
I helped tear out steam radiator coils from a car. They were interesting in that they were two concentric tubes. The steam came up from underneath of the car halfway down on each side of the car. And split off into two coils one going forward and the other going back. The steam went the length of each coil in the inner copper tube and at the end of the radiator coil it fed out into the larger copper pipe with the fins. And went back to the center of the car and went down through the floor.

The concentric piping acts as a kind of countercurrent heat exchanger: the hottest entering steam is adjacent to the coolest condensing steam, so the effective length of the half-car run will operate at about the same radiating temperature. There are ways this might be adjusted when the car has been in service for a while.

I had a handful of steam heat manuals that I sold a number of years ago so this is from memory.

The vapor units that were installed in diesels were a flash type boiler so they run better when they are worked hard so a higher operating pressure is expected.

The comments about 10psi per car is consistent with what I remember in the books and with the now deceased retirees of the GN and NP who recounted what it took the maximum pressure the steam generators were capable of keep the empire builder and north coast limited warm across the prairies in the deep of winter.

Most of the fittings and pipe i've seen on the trainlines were SCH 80 so 300 psi would not be outside of their spec and the last iteration of the flexible conduits (2-1/2') were rated for 300 PSI. the older 2" flexible had a lower rating of 200 PSI and the hose connectors were 150 PSI which was the hose avail of the time. Goodyear steelflex steam hose of today is 225PSI.

The heating loops are a low pressure, <15PSI, circuit so the temperature is comfortable to the passengers. The control valves are basically a pressure regulator with a built in trap to maintain a constant temp/pressure in the loop. This ties back to the high trainline pressure to push enough heat down the trainline so every control valve has a differential to work against.

The philosophy regarding traps appeared to be if it might be a low spot of it's been so many feet since the last one, add another trap because frozen pipes are... well... use your own euphonism

Heating coaches takes an enormous amount of energy. when Mid COntinent was running steam the smaller engines could heat the train or pull the train, but not at the same time.

as usual, your mileage may vary.

Regarding the question of trainline pressures, the following is from the Amtrak OK-4625-74G steam generator maintenance manual, NRPC CMO-118, dated 10/78, along with the following quote: "Or, what you always wanted to know about steam generators... But didn't know whom to ask."

Parts of this document are laid out in a q/a arrangement, and below are a couple of the questions and answers.

Q. What pressure should the Water-By-Pass Regulator be set for? (The water bypass regulator establishes the operating pressure of the Vapor Clarkson 4625 boiler)
A. You have two choices, 200 or 230 psi. 230 is better.

Q. Why?
A. 230 psi steam is hotter. It is the heat that the cars need.

Then there is this one:

Q. What is the minimum number of steam generators that should be used for any given train. What is the number of cars that one steam generator will heat or cool adequately?
A. That is a difficult question to answer. Each steam generator produces 3,350,000 BTU per hour. Due to the many variables involved, the best rule of thumb is to use only the number of generators necessary to maintain 180 to 230 psi trainline pressure, with the water bypass regulator set at its maximum position. USE THE MINIMUM Of STEAM GENERATORS REQUIRED. (I'm not yelling, Amtrak was!)

In our case (and I'm sitting in front of it now, watching it run), our steam generator is in an ex CN steam generator car, and is the same model discussed above. Ours has a four position water bypass regulator, allowing four different boiler/trainline pressures, 125, 160, 200, and 230. Those are the low end, as the boiler has a 45 psi differential between off and on, so a setting of 125 will cycle off at about 170 psi. So, your trainline pressures will be going up and down as the boiler cycles. Amtrak stated that most boiler troubles occured with boilers that were cycling on and off, hence their comments to use the minimum number of boilers so the ones that were running were preferably running flat out all the time. Ours, conversely, seems to operate just fine cycling, with none of the issues noted in the Amtrak manual, but it does get doted on, so that may be why.

As Overmod eluded to, steam powered a/c requires pressures around 200-230 psi, so yes, trainline steam pressures needed to be right up there, winter and summer.

Another thing to keep in mind, is shut down of the system. We generally run ours at the 125 psi setting, but about a half-hour prior to shutting down, particularly if ambient temps are below, or forcasted to fall below freezing, we'll run up the system pressure to 160 psi, to increase the heat in the trainline. Then, just before shutting off the steam to the trainline, the rear trainline valve is fully opened for about 5 to 10 seconds, which serves to blow any pockets of water out of low spots in the trainline, until dry steam appears at the rear. At this point the valve at the steam generator car is closed, with the end result being not enough water left in the trainline to cause any damage when it does freeze. If you were running a really low pressure trainline, I'd be concerned you wouldn't get all the water out of it when shutting down, leading to more problems in really cold conditions.

The 10/20 psi/car numbers date back to when it was just providing heat, and earlier systems had trainline pressures inside the car. They also generally had facilities to keep cars on steam in cold weather when not in service, a luxury I don't think any of us have. I too, would not want to run the high pressures in equipment equipped with hose connections, and we have replaced trainline on several cars due to corrosion.

The later systems used low pressure steam inside the car, and the newest using a small tube inside the larger, and was intended to have the outer, return tube half-full of condensate to conduct the heat of the steam in the inner pipe to the outer wall and fins of the larger tube.

As earlier noted, there should always be a bit of steam allowed to escape the rear (and front!) connector, to keep steam flowing which will prevent the freezing of any pockets of water in low points.

We're still heating two out of eight cars with steam, but parts for cars are next to unobtanium, and boiler parts just recently got harder to get, as Vapor Power has been sold to another firm, with the new folks not appearing to want to be as helpful to us small fry customers as they used to be. So, as we restore cars to service, they are getting electric heat and HEP. The other advantage is the ability to heat the consist for cleaning or other maintenance when the steam generator is not available, which makes those chores far more palatable to volunteers.

Kent

Your remark about conductors calling for more steam seems to indicate that your cars no longer have the ability to reduce the trainline steam pressure before the coils. As you say these parts are hard to find. I'm sure that vast stocks of such were thrown away after Amtrak took over passenger service. Steam heat is still very common in the Northern part of the country and bigger cities but adapting stationary parts to rail use may be difficult and maybe forbidden by FRA rules.
If you are having to run trainline pressure in the coils then I'm afraid that coil failure lurks ahead and heat will be elusive.

Kent's post brought back memories of our exclusive use of steam heat on the Grand Canyon Ry in the early days of the operation.

From GCRY Employee Timetable No. 5 (1993):

Special Instruction (Rule 850) - When steam heat is required on passenger trains the Conductor or Brakeman will notify the Fireman. Whenever the steam heat is turned on the maximum pressure will be used until the train crew requests the pressure be reduced after observing that all water is blown out of the rear car. A minimum of 80 psi as indicated on the rear end of steam heat line will be maintained on the steam heat system while being used.

During our winter operations, working steam heat was a must in the former SP Commuter Cars and generally also a pain in the ass. Trying to keep the system from freezing after cutting off the locomotive was always a challenge along with the maintenance of the system itself. I recall the steam heat connections between the cars being especially "challenging" and not in a good way. With just a steam locomotive on a train without an auxiliary water car, use of the steam heat (water) had to be carefully monitored by the engine crew so as to assure we had enough water to reach the Grand Canyon. Many times, I would have to reduce the steam heat to an absolute minimum pressure or if there was not a danger from freezing, shut off completely to conserve water for the locomotive. When double heading with the Alco diesel behind the steam locomotive, the steam heat boiler in the Alco was used. This would require a fireman on the diesel to monitor that boiler and assure steam heat was available at all times when needed.

Kent may have more comments on the GCRY system as well since he was probably more involved with maintenance.

I am glad I was able to experience the use of steam heat on preserved equipment being used in regular service....but never again....

Thanks for the memories Kent!

Other than the maintenance and testing requirements for steam heat boilers as outlined in 49 CFR Part 229, FRA has no other rules regarding steam heat that I am aware of.

MDR

After a couple of days to recover I'll offer some firsthand insights from the Santa events at Mid-Continent Rwy. I was not involved in the initial installation or lash-up so I cannot answer the "Why was it done that way" questions although we have made some improvements.
We are using an oil-fired boiler that was built as a portable culvert steamer for a municipality. It is a 2-pass firetube type rated at 30 hp. It is piped onto the trainline header in place of the 2 Vapor-Clarkson generators that were junk when received the car. Steam is piped from the 1" outlet on top of the boiler through a pressure regulator and into the 2 1/2" header line. We adhere to the 10lb/car rule of thumb when we can attain it. On cold events we are lucky to attain 5 - 7 lb total at the header because the demand far outstrips the capacity of the boiler. We are heating 4 of the Boonton type commuter coaches which use the earlier style direct heating pipes set up in 4 zones for each car. The train line is tapped for each side of the car and each tap is split for the A or B end of that side of the coach. Each of the 4 splits has its own trap. We also have a trap on the train line at the end of the consist.
One of the difficulties is the 1" line of the boiler dumping into the cavern of the 2 1/2" header and it will wire-draw somewhat. That is at the same time a bit of a blessing so it doesn't suck all the steam out at once and we have a small chance of firing against the load and keeping up enough pressure to run the injectors. More often than not we throttle the steam going into the regulator to keep up enough steam pressure in the boiler for the injectors.
At maximum output and constant fire the boiler consumes about 8 gallons of fuel and about 100 gallons of water per hour.
Even with that low of pressure (5-7 lbs) in the train line we can flow enough steam to push out the water & operate the traps. With a bit of patience and a few hours of heating before train time we can keep the passengers comfortable. When we get into single digits & below we have overnight hostlers to tend the boiler & keep steam on the train.

To the comment from Paul D about the difficulties utilizing smaller engines I will say it was probably partially self-inflicted. The Northwestern did use some of the R-1's in some back-up commuter service & that is why the 1385 was outfitted with steam heat connections to each end. Coming off the cab turret is a 2" globe valve to feed steam for heating which originally then went to a Leslie 2" reducing valve. When I fired her in the late '90's the Leslie valve had been previously replaced with a more modern 3/4" or 1" regulator because "A 2" regulator was too expensive". This meant that the wire-draw through the regulator limited the amount of steam that could be delivered to the train line. Above 20°F we could keep up but below that point it was a struggle.
Adding insult to injury, the #2 only had a steam heat connection on the tender & none on the pilot. When it was used instead of the R-1 it meant the train could only be heated for half the trip because we cut off and runaround the consist at each end of our railroad. It also employed the same size (too small) regulator.

All in all, steam generators run best at or near their limit while a packet saturated boiler will deliver the driest steam at its MAWP. If you go to a packet steam boiler I would suggest reducing your train line pressure if possible/appropriate. Be sure any boiler you are looking at can deliver as many pounds-per-hour of steam as you are demanding from your current setup. One thing not mentioned is which style of heating system is in your coaches? Is it the earlier single-pass pipes or the coaxial style fin tubes?

I hope something useful can be gleaned from this ramble.........mld

Clayton Industries produces steam generators which operate similar to the Vapor Clarkson/ Vapor International and I believe the UP boiler dorm "Howard Fogg" is equipped with one as well as the shop. I have three gas fired units and am pleased with them. My contact at Clayton is: James.Letcher@claytonindustries.com

We have a representative from Clayton coming this week to discuss our operation.



We have the early style single pass pipes.

I presume that a 'packet' boiler is actually a package boiler -- many are forced-combustion multiple-pass boilers that have a very long effective flame/gas path with multiple 'folded' nested return passes. Many of these can effectively do heat exchange lower than the condensation point of combustion water, which can afford a significant boost in overall operating efficiency. That is particularly valuable if some form of steam injection is in use to meet ever-more-stringent NO.NO2 "requirements".

If I remember correctly, a great many package boilers are designed for 'typical' building heating pressure of 15 to 30psi. You would need very careful insulation of the steam lines and hose connections to make any real use of such pressure effectively; someone should probably do a heat-balance diagram with some empirical mass flows from existing equipment to see if there is any workable method.

I helped design and build the system at Wilmington & Western. The 15 PSI package boiler did a fine job heating 5 cars and I'm certain it would handle a few more. Once the train is warmed up the steam flow is actually cut back pretty far except on the coldest of days. The system has been in use since 2018 and has been very reliable.

I once uncoupled Cut Bank Pass from another steam heated car while on a curve. The steam heat lines were not connected but hung up on each other as the cars uncoupled. The line ripped right off just past the valve. There was almost nothing left of the main pipe. We ended up replacing about a 3' section because that's how far we had to go back to find something solid enough to actually thread. The car was donated in 1969 and the liberation of the steam line was around 1985. I assume the car was in use before donation but had never had steam connected since. I assume the lagging held moisture on the outside of the pipe, but it could have rusted from the inside as well. If you want a continuous nightmare, activate a steam heat system without properly rebuilding the system. Just go ahead and replace all the pipes. Otherwise, it's like putting rotten superheater units in a locomotive fresh out of a 1472 - you will regret it every time you have to pull all the front lower units to get at the leaking rear top units. Steam heat leaks will only rear their heads when you need the car for generating revenue. I admire, yet feel sorry for, anyone willing to do what it takes to successfully put together a train of steamed cars. It really is preservation on the highest level. The smell of steam and spitting condensate traps can't be replicated with electric heaters.