Spotting Tank Cars at International Paper

Paper plants have tons of piping and tanks to handle the process of morphing wood into a liquid slurry so the fibres can be manipulated into paper. I’m amazed at the complexity of it all, and I really only understand the broad strokes of it.

The photos that I have of the International Paper plant on Tonawanda Island (a factory that faded into history long ago) are taken from a great distance and show only the general arrangement of buildings. I have no close shots of what the details of the piping and tanks looked like, so I’m faking it by referring to photos from other paper plants. The challenge with this approach is the fact that, like any industrial process, paper making has always been in constant evolution. I have to try to avoid anachronisms by being alert to practices that seem more modern than my era. I’ve found very few photos of paper plants from before the early  ’70s, so I’m not to concerned with reproducing practices that were out of date by the early 1970s.

Here are some photos of the progress I’ve made to date on the area of the paper plant where tank cars are unloaded. One thing that I’ve noticed is that tank car unloading was a much less sophisticated process back then. Hoses were dragged along the ground and connected to the appropriate fittings the car and then the contents were pumped out. So that’s the impression I’m trying to create in this area of my layout: a dirty and cramped space where everyone has to be paying attention while trains move along at walking speed.


Penn Central 9574 is standing in for an ancient Alco S2 that was having some mechanical issues. Tank cars are being spotted in order to be emptied into storage tanks at the plant.



Here’s the ground-level view of the same scene as above.


The positioning of the cars is critical because the pumps and hoses into the building on the right are specific to the different chemicals used in the paper making process.


The brakeman has gone inside to find someone who can advise exactly where to spot these cars. Better to take the time to place them correctly the first time. In the meantime, the engineer has gone into the plant to use the vending machine and the washroom. This could take a while.




  1. Hey Hunter,

    You’ve done a good job, looks like a big some what old paper plant to me. Safety first in that place!!

    Best, Scott


  2. Hi Hunter, I have enjoyed your progress modeling of your Paper Mill.
    If I could add from my 1974 imagination “the brakeman would find the Mill phone ( just inside the doorway) and call the number for the Bleach Plant Operator informing the Bleach Plant Operator that the Chlorine car is spotted at the dedicated sight ready for unloading. (the Bleach Plant operator is in a building 5 stories high with a special operating room that will be pressurised to try keep out any chlorine gas from the washer process out of his control room. There will also be an escape SCBA if needed. Lets hope not). They could also talk about when the rail crew could pick up the empty Chlorine car and bring the second Chlorine car in for unloading followed by a Sulfur Dioxide tank car. Chlorine and Sulfur Dioxide rail cars ( and trucks) had dedicated unloading sites. These rail cars are usually accessed by a catwalk to the dome on top of the tank car where the hose for unloading is connected. The Bleach Plant Operator will then contact the Bleach Plant helper and the Bleach Plant pipe fitter ( by the use of radios) to head on over to connect the tank car for the unloading process to begin. The unloading will not start until the locomotive and train crew are safely out of the area. The B.P. Helper will put up the “Blue Flag” and make sure the “Derail” is in the correct position. Then the helper and pipe fitter will put on their SCBA safety equipment turn on the warning lights ( to warn employees’ of the unloading taking place in case there is a leak) and proceed up the stairs to the cat walk. The bridge plate will be put in place to allow safe access to the dome of the tank car. Working together they will hook up the hose then notify the Bleach Plant Operator they are ready to unload the tank car. Once the Operator gives the go ahead the valves will be opened setting the process of unloading to begin. They will also monitor the hose connects and fitting for any leaks. Depending on the Mill this process could be completed in 6 hours to 24 hours. Once the Chlorine tank car is unloaded the B.P. helper and B.P. pipe fitter will shut off the valves, disconnect the hose and check the tank car valves for any leaks. When all is clear the alarm lights will be turned off, the “Blue flag” will be removed and the “Derail” set back to allow the locomotive to pick up the now empty tank car.
    In my imagination the locomotive crew works this Mill site on a regular basis. Any new crew members would have to be trained as to where to drop off chemical cars and have some safety orientation . The Locomotive should have a Mill map of trackage and where the different cars are to be spotted. Even in 1974 safety was a major concern handling Chlorine, Sulfur Dioxide, Caustic, Sulfur, and any other dangerous chemical had strict procedures. ( My guess would be in the locomotive will be escape respirators for all the train crew plus a spare or 2) Some of the starch alum and fillers plus other additives would have hoses laying along side the track and be dragged to a tank car or covered hopper for unloading. These rail unloading sites were an after thought as originally these chemicals came in 50, 70 or 100 pound sacks in a box car. Moving to tank cars or hoppers most Mills did not have dedicated space so long hoses were used to connect with where the Mill storage tank was located.
    Depending on how many Paper Machines your Mill has will depend on how many Chlorine and Sulfur Dioxide cars need to be delivered each week. 1 to 2 machines will have 2 to 4 chlorine and 1 to 2 Sulfur tank cars. 3 paper machines 4 to 8 chlorine cars and 2 to 4 sulfur cars.
    Enjoy switching your rail cars at your Paper Mill. It can be a very busy job. Most Pulp and Paper Mills operate 24 hours a day 7 days a week, 360 days a year. They consume a lot of items to produce Pulp and or Paper.
    Regards, Rick


      1. HI Hunter; I do not mind at all ask away.
        I was hoping you would not mind my ” 1974 imagination of your operation”
        I will say that I did not work at the Paper Mill you are modeling or for International Paper. However I spent a life time in the Pulp and Paper industry starting back in 1965 so if I can, I will help. If I do not have an answer maybe my work friends will be able to help out with an answer.
        I was going to visit your page on the box cars being dropped off for a load of paper product(s).
        Regards, Rick


  3. Hi Hunter,
    Well I did visit you page on the box car dropping off to pick up paper and wrote up what I could imagine happening however some how I lost it to a computer glitch. sorry about. I’ll try again some other time.
    Regards, Rick


  4. I’ll get right into then.

    What’s SCBA?

    Why was chlorine unloading followed by sulfur dioxide? Is sulfur dioxide around the same density as chlorine? I ask because I need to figure out what kind of tank car models I’ll use for that commodity.

    I plan to put a bunch of hoses on the ground in the scene that is in the photos, so now I know why they were there. In the photos of the plant, I can’t find an elevated platform to get to the top of the tank car. Granted, I don’t have very detailed photos. Is it possible that they didn’t have one, and instead used some sort of rolling steps or simply used the ladders on the sides to access the dome of the tank car?

    More questions to follow.


  5. Hi Hunter,
    S.C.B.A. is self contained breathing apparatus. “Scott is one manufacturer of this equipment. You see fire fighters with the air tank on their backs and a full face mask. The 2 people hooking up and unhooking the tank car are subject to a leak. To fix the leak they need to be able to see and breath. Both Chlorine and Sulfur Dioxide are shipped as compressed gasses about 2 1/2 times heaver than air. If a leak occurs anyone in the area will have a difficult time to breath. The gasses also make your eyes water. So it is difficult to breath and see where you are going. I believe Chlorine gas was what was used in WW 1 and killed may troops as they had no defence when the Germans first used it. Some Mills only used a canister respirator with a full face mask to work in however my experience has been that those are good for escape use, not staying to fix a leak. Did a leak happen every time? No but the potential is ever present.


  6. Hi Hunter,
    On the unloading sequence, most Mills I have seen had a spot for the Chlorine car(s) and just along the track was the spot for the Sulfur Dioxide car. The train crew would bring in the Sulfur Dioxide car then the Chlorine car(s). Yes the density is about then same. I have not seen an exact model of the SO2 cars used out west but I believe the new release tank car from Kadee would be close. I understand their model is based on a 1944 tank car which would work. The Sulfur Dioxide tank cars had the words in white letters at the end of the car. I will explain the Pulping process in a future reply and that will help you understand why, what, and when for the different chemicals. For now SO2 is used to make “super bleach” stronger than Chlorine but more expensive so they use Chlorine and then add “supper bleach” to get the brightness of the pulp the customer wants. SO@ is also used to brighten wood chips.
    I did try to check out your photo of the Mill site and I did Google the Mill as I was looking for any tell tail signs of a platform for unloading the tank car(s) from the top. Like you I saw nothing to indicate a platform. There might be a movable set of rolling steps with a platform. Or yes they could have just dragged a hose under the Chlorine and SO2 tank car. I have not seen it done but that does not mean it did not happen. What I wonder is if the elevated platform was located under cover to keep snow and ice off. I have seen several Mills where the platform is under a roof or inside a building out of the winter weather.
    Regards, Rick


    1. Great info Rick! Let me brainstorm a few things that I think I’ve gleaned from the photos, and I invite you to comment on whether you are seeing the same things in the photos of my plant on Tonawanda Island.

      Firstly, I think the tank cars were all unloaded in the same place. The aerial photo of the west side of the plant (the Niagara River side) shows a couple of storage tracks that stretch out to the north tip of the island. Just off of those tracks is what looks like a conveyor covered with galvanized metal cladding. I assumed this is a conveyor because I can’t imagine why a pipeline would need to be covered. Perhaps this was for unloading kaolin, or some other powder material (alum)? Whatever that thing is (conveyor or covered pipeline) it passes to the north of the tall concrete building with tall windows that I’m assuming is the recovery boiler.

      Still on the west side of the plant, there was a fan of three very short tracks that angle off toward a large grey metal building just north of the pulp storage tank/tower. It looks like these three tracks are the only place that tank cars were unloaded. My best guess (and I welcome your input) is that they probably unloaded all liquids in this area. I envision an arrangement where a number of different pipelines converged in this area. Each pipeline might have had a different set of hoses and connectors that were dragged out to the tank car and connected to the appropriate network depending on the commodity. That is what I’m very loosely depicting in the photos of the chlorine tank car being spotted. Really, it’s depicted ‘operationally’ more than visually. The scene is on its way to looking believable, but it’s not an attempt to reproduce what was actually there.

      Now, moving to the east side of the building that probably houses the paper machine at the centre of the plant, I’ve wondered about the possibility of a spot for one tank car. An aerial photos shows some boxcars being spotted on a dock in that area. I can’t clearly make out how far back into the maze of tanks and towers that track goes. It’s possible they could have unloaded a tank car if that track goes back into the maze of tanks and pipelines. I haven’t depicted that on my layout. Instead, I’ve put a short track fanning off of the one where the boxcars are spotted. I’m depicting a second put a second tank car unloading area here.

      This brings me to another question. That second tank car unloading area is next to my model of the recovery boiler. I’ve read that black liquor is recovered at the recovery boiler, hence the name, and used as an energy source for the mill. Would it be realistic to represent the outbound shipment of black liquor in tank cars? Did paper mills burn the black liquor at the power plant? Is black liquor a raw material for another industrial process, and thereby a saleable commodity for the plant?


  7. Hi Hunter,
    Lets start with the covered conveyor with a galvanized roof. Well it could be for Kaolin my guess is not likely. Kaolin is a very, very fine powder like baby powder so any gust of wind and we would have a fine grayish white powered everywhere,. Kaolin can be shipped dry in hopper cars . When the hopper car is spotted a hose is connected to the bottom outlet and air is pumped in to create a flow of the powder. Kaolin is mixed with water and stored in a tank at the wet end of the Paper Machine. When you see a tank car with Kaolin the clay is already mixed with water and ready to be connected to a hose and pumped into the storage tank.

    All the different powdered chemicals would be pumped in hoses to a storage tank. Each hose and tank is dedicated to one type of product being handled. Any cross contamination is not good for the equipment, the pulp or paper and the employees. So mix-ups will have disastrous results. So yes there are a lot of hoses and pipes and tanks. Each with a very specific task. ( that is why some places in the Mill look like a spaghetti bowel, pipes going every where.).

    I wonder if the covered conveyor with a galvanized roof is for chips on their way to the batch Digesters. I was looking for a cement building 5 to 6 stories tall in a rectangle or square shape. This Mill should have a number of batched Digesters to feed the Paper Machines. ( my guess would be somewhere between 8 and 14 depending on the number of Paper Machines.) There could be a continuous Digester on site say a single tower 150 feet to 200 feet tall with a covered conveyor reaching up to near the top or could be located next to the building with the batch Digesters. Batch Digesters date back to the beginning of Pulp And Paper making ( 1890). Continuous Digesters were in the 1970,s and are used mainly now in any new installation for the pulp process.

    ON the east side of the building we think is the Paper Machine Room ( also known as Machine Hall in some Mills). where there are some box cars spotted on a dock. My guess is that is the unloading platform for all the pallets of chemicals, dyes, and additives. This could also be where spare parts and equipment is unloaded. With the Paper Machine Room next to the unloading dock all the pallets of chemicals ,dyes and additives would be transported by forklift into the basement of the Paper machine room. Plastic wrap and plastic or steel totes we see today were not used in 1974. Most items came in sacks or steel drums of 25 gallon or 45 gallon. The Mill needs a location where forklifts can drive in and out of box cars to unload the box car, or off and on flat cars. The Mill needs a short drive in the outside weather to a dry location for storage. The Mill would not want to bring any chemicals into the shipping warehouse in case something spilled and the rolls of paper got contaminated. This might be the location where large items were off loaded like a new electrical transformer. The P&P industry uses a lot of electricity and from time o time need to purchase new transformers. If you wanted an interesting load these transformers are big and some arrive in a drop well flat car. Some a bit smaller on a regular flat car. They use a mobile carne to unload. Also large metal rolls and drums would need to be transported in and out of the Mill for repairs or replacement.
    All these additives would be stored somewhere close to the wet end of the paper machine where they are used. The storage room could be called a “Raw Materials Storage Room“.
    Yes there could be a tank car unloading site farther past where the box cars are spotted. I wonder if they had a loading site for “Turpentine“

    I need to spend some time typing out the Pulping process for you. From chips to Digester. From White Liquor to Black Liquor to Recovery furnace to Weak Black Liquor to Green Liquor to Lime Kiln. to Recaust and back to White Liquor. The whole process is a big circle that will be better understood after I type it out. The Liquor is expensive and therefor Mills have Recoveries to recover and reuse the caustic over and over and over adding a little new fresh caustic as needed. The Recovery Furnace is right next door to the Steam Plant Boiler(S) (and is part of the Power Plant) as the operators of the Recovery needs a pressure vessel operator`s ticket same as a Steam Plant Boiler operator.
    Sorry no out bound shipments of Black Liquor from the Mill. However we are looking for a Lime Kiln very similar to a Cement Plant Lime Kiln. This should be a Long thin tube with a furnace at one end where the Lime Rock is added and a small building at the other where the bucket chain lifts out to cooked lime.

    The Recovery and Power Boilers are usually in a building made of a steel frame covered with corrugated fiber board that would fall off the building if there was a melt down of one of the boilers or recovery furnace. A cement building would suffer a lot of damage and have to be torn down. or expensive repairs. The corrugated siding would be an easier fix as is the steel frame.

    I might have missed something but this is a start. If in this set of questions I have missed something please ask again.

    Sorry it will be a few days before I answer as I am back to work.
    Regards, Rick


    1. I didn’t consider that the plant would have a lime kiln. How does lime factor into to making paper?

      I don’t see anything that resembles a lime kiln. Is it possible it was inside of a building?

      Also, at some point when you write up the process for me, can you talk about the materials that might have come into a plant by boxcar, and where those materials are typically sourced (if that’s possible to narrow down)?


  8. Hi Hunter,
    Today I’ll try explain the process of turning wood chips into pulp.
    There are two different processes using two different types of Liquor.
    One type of pulping process is “Sulphite” where Red Liquor is used.
    The other pulping process is the “Sulphate” process where White Liquor is used.

    We will be looking at the second, more common process.
    Your Paper Mill has wood chips from Canada delivered by box car to an area where the Mill use to stock pile wood logs. Depending on the type of pulp and or paper the Mill wanted to produce depends on the type and or types of wood species that would be at the Mill. I noticed in checking out your Mill that they had Poplar logs on site so I wonder if that is the type of wood chips they received from Canada? Poplar is a hard wood species used in some grades of pulp and paper. I also saw only one pile of wood chips indicating to me that the Mill used only one type of wood species (fiber ).( not to be too confusing but some mills have 2 or 3 or 4 or 5 types of wood species for different fiber requirements. Each would be cooked in a different digester and kept separate until required in the manufacturing process. Oh yes more tanks and pipes going in many different directions.).

    Why take a log and chip it? To be able to break down the organics that hold the wood fibers together. There is a perfect chip size one inch to 1 1/4 inch long by one inch wide by 1/4 inch thick is considered idea for the Kraft Digester process. This should result in a large number of long fibers that interlock in many different directions to form a strong sheet of paper. A wood grinder makes smaller fibers that are much shorter but cheaper and quicker to make. This is what is called “Ground Wood” a special sharp stone with a big steel ram pushing the log into the stone. The log is ground with wood fibers pulled off the log. Sawdust chips are short fibers thus little strength. Also the Kraft process results in about 86% of the wood fiber used in the making of paper. Ground Wood results in about 68% of the wood fiber being used in the making of the paper.

    So lets assume one type of wood species as I only saw one pile of wood chips. A number of Mills would feed the open pile of wood chips onto or into a conveyor. This could be a belt type or a blower type pipe operation to move the chips along. Most Mills I have seen move the wood chips up to a storage bin building sometimes called a “Chip Barn” or “Chip Silo”. These Barns or Silos keep the chips dry and clean before use. From the storage bin the wood chips are drawn off from the bottom of the storage bin an long and up to the Digester building. There are 2 types of Kraft Digesters. A batch Digester and a continuous Digester such as a “Kamyr” ( the Kamyr digester is a tall round structure 150 to 200 plus feet tall with a chip conveyor running up to near the top of the tower. There is a steady flow of wood chips into the top of the tower with piping on the outside to feed white liquor and some black liquor added then farther down the tower pipes with steam is added and the cooking begins.)( there would be a tall most likely a cement building right next door to house the operating and controls.).
    The Batch Digesters are located on the 5th floor of a concert building. There will be 6 to 16 ( could be more or less) Batch Digesters in a row or several rows. The wood chips come up from ground level on a rubber belt conveyor and drop onto another rubber belt conveyor that is located in the roof of the 5th floor running over top of the batch Digesters. The Batch Digester is a large metal cylinder that has an opening hatch that lifts and swings sideways out of the way to allow a large funnel to be placed into the opening and up to the roof conveyor carrying the wood chips. A “Sweep” ( this is a device that blocks the wood chips from traveling farther along the conveyor so they are diverted off of the top conveyor causing the chips to fall into the funnel ) diverts the chips from the top wood chip conveyor into the funnel and the chips fall into the digester. On average 5 tons of wood chips are added for one cooking or “Batch”. Once the wood chips are added the “Sweep is lifted and the funnel is moved out of the way. The next job is replacing the heavy metal lid. A small over head crane or chain block has helped open and hold the heavy lid out of the way while filling of the wood chips now the lid is brought back into position and lowered into place. The Asbestos gasket ( this is 1974) is checked to make sure the Batch Digester lid will seal tightly. we do not want hot liquor, steam and cooked wood chips leaking out. With the lid in place the swing bolts will be pulled up in place and a large air powered ratchet will tighten the nuts. ( much like a pressure cooker lid with wing nuts). With the lid safely in place White Liquor is added to a predetermined level> about 80% of required liquid. Also added is strong black Liquor at 20% to top off the liquor required for the “Cook”. at this time the “Knots” from the last Cook will be added to this “Cook”. Now the steam is added into the Batch Digester and the cooking process begins. Around 2 1/2 to 3 hours the “Cook” is ready to be “Blown” out of the Batch Digester. There is a valve at the bottom of the Digester that is opened and if all goes well the “Cooked Batch” flows out. ( I will not cover all the things that can go wrong and slow or stop the digester process at this time.).First stop for the “Batch” is the “Blow Tank”. This collection is made up of very hot cooked wood fiber, knots, weak black Liquor ,steam and by products. Gasses from the cooking process are collected here and funneled off. Turpentine is one of the Gasses that could be collected and distilled in a tank for shipment to a paint company. (Or it could be sent to the Lime Kiln to be burnt like rocket fuel.) Other gasses are vented off. ( thus the smell of a Kraft Mill). The wood chips have now become “Brown Stock” and need the “Weak Black Liquor washed out before the next process can take place in the process of becoming pulp or paper. The Brown stock moves between storage tanks and washers that are large drums with wire mesh to allow water to wash away the black liquor and knots. The Knots go to their own storage tank and back into the next “Cook”. The Week Black Liquor is drawn off to a dedicated storage tank. There should be 4 brown stock washers in a row then the stock is pumped into a storage tank ready for the next step.

    Let us follow the “Week Black Liquor’ process for a moment. Week Black Liquor is sent to the “Evaporators” ( located in the Recovery section of the Steam Plant.) The “Evaporators boil off the water ( water from steam and moisture from the wood chip cooking process) Week Black Liquor is now Heavy Black Liquor. About 72% solids. If the Strong Black Liquor has too much water it could boil and explode in the Recovery Furnace ( a very dangerous and damaging result). Too thick and it will not pump so this process is critical. The Strong Black Liquor is burned in the Recovery Furnace to burn off the “organics” that were dissolved from the wood chips in the cooking process. Burnt Strong Black Liquor leaves the Recovery Furnace much like molten lava and is called “Smelt” Weak wash is added to the Smelt and this becomes “Green Liquor” This liquid travels through a Clarifier and goes to a “Slaker” where Hot Lime from the Lime Kiln is added ( at the Recaustic Department part of the Kraft Mill). This “Green Liquor and Lime is pumped to tanks where caustic Soda is added. Give this mixture time to React ( chemical reaction) and the Green Liquor turns back into White Liquor. The next step is to pass this liquid through pressure filters that separate the “Mud’ ( lime and some chemicals). out of the White Liquor. The “Mud is washed twice in pressure filters. The first wash is where the white Liquor is piped off to a storage tank and back to the Batch Digester for another Cook. The second wash results in a liquid called “Weak Wash” that is pumped back to the Recovery Boilers to make “Green Liquor” . The “Mud” that is filtered out is pumped back to the Lime Kiln. Here the impurities are burnt off and the “mud” turns back into Lime. And the process starts all over again.

    Following this process along is much like a circle where the Liquor is White, cooked becomes Weak black, water removed becomes Strong black, burnt becomes smelt, added to weak wash becomes Green Liquor,lime and caustic soda are added and becomes white ready to go through the process again. The Lime also has a circle of it’s process.

    Would the Mill you are modeling ship the black liquor out to another Mill to be processed? I do not think so as the Mill has a Recovery. But like I said I didn’t work in this Mill. Is Black Liquor used in another type of process? Not that I am aware of. These chemicals are expensive so recovering and reusing was the normal operation. If there is no Lime Kiln would they ship in Lime and not Lime Rock? Possible. The Lime needs to be heated before being added to the Green liquor but they could have a method.
    Hope this helps your understanding of the Kraft Digester process of making Kraft Pulp.

    Next time we will look at the bleaching process as now we have the “Brown Stock” ready for unbleached Kraft Pulp or Paper. Your Mill produces bleached paper.
    Regards, Rick


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