Tank cars roof walks

[Rambo2]

I notice some tank cars have walkway and handrails the length of the car some have short or none .Any reason for them?

[tree68]

Depends on how they are loaded/unloaded...

[CShaveRR]

The reason for any walkway or ladder would be access to the manway ("dome", in the old days).  The cars with full-length walkways have no side ladders up to the platform.  Those with partial-length walkways may have more than one manway up top, or--more likely--a ladder at the end of the walkway, moved away from the center of the tank by clearance limitations.

[MMLDelete]

I see that on a lot of the current, huge tank cars, the top of the tank at each end is higher than in the middle? What's that all about?

Is the manway/dome an access point for cleaning purposes? Why was the dome necessary before, but not now?

[Rambo2]

I thought it was more on what comodity they carried.

[Rambo2]

I'll look for side ladders next time i'm train watching.

[tree68]

Lithonia Operator

I see that on a lot of the current, huge tank cars, the top of the tank at each end is higher than in the middle? What's that all about?

Those are going to be bottom unloading cars.  The sway-back also allows the dome area to be "higher" than it would be for a purely cylindrical car, potentially increasing capacity.

Lithonia Operator

Is the manway/dome an access point for cleaning purposes? Why was the dome necessary before, but not now?

The dome itself is there to protect whatever is on the top of the car (top fill fittings, pressure relief, etc).  I believe you'll find all tank cars have a manway.  

Cars that always handle the same commodity don't have to be cleaned all that often.  The fact that there is still residual product in the car is why they are placarded even when "empty."

A general service car that is going to be used for a different commodity will have to be cleaned, as will a car that has to have work done on the tank itself.   This may also apply to some food-grade commodities.  There are companies that specialize in that.  

Disclaimer - I have no personal interest in GATX.  But they have a website explaining some of their tank car products:  http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail+North+America/Products/Equipment+Types/Tank/

 

[Juniata Man]

Lithonia Operator

I see that on a lot of the current, huge tank cars, the top of the tank at each end is higher than in the middle? What's that all about?

Is the manway/dome an access point for cleaning purposes? Why was the dome necessary before, but not now?

 

Manways do provide access to the interior of the car for maintenance.

Tank cars today are equipped with pressure relief valves / vents.  These serve the same purpose as the old tank car domes.

[Deggesty]

Yes, any container that has handled hazardous material, unless it has been thoroughly cleaned, is still hazardous, even though all material that is easily removed has been removed. The bill of lading for "empty" drums and gas cylinders will have the notation(s) "residue" for each such item. 

I, of course, never handled tank cars, but I shipped many an "empty" drum  or cylinder that had been filled with a hazardous material. I had certification that I had been trained properly for shipping by air or highway--and had to be recertified every other year for air and every third year for highway. I had to make sure that trucks had the proper placards.

[MMLDelete]

Why do some large modern tank cars have a dip in the center, like the one on this page? (Scroll down a little, see the first tank car photo.)

Also, on such cars is the bottom of the tank also not straight? That's hard to tell in photos. If the bottom of the tank is parallel to the top, and juts down a bit, with the center as its lowest point, my best guess is that makes the liquid flow better to the outlet, which I would assume is right at that low point. Yes? No?

[PNWRMNM]

I will speak to the dome/not dome question.

The first tank cars were for crude and refined petroleum products. They had expansion domes and cars were loaded shell full, leaving the dome for expansion in transit. The first modern specification for liquids, as opposed to compressed gas, was the ICC 103. Cars for flammable liquids had a 2% dome, and cars for acids had a 1% dome. The difference in dome size was obvious at a glance.

About 1960 specification 111A cars were introduced for liquid service. The 2 or 1 percent outage was/is carried in the tank. Liquid level is indicated by a fixed indicator. The rule is load no more than to the bottom of the indicator.

Of course, if the product is heavier than that which the car was designed for, then the gallons to load must be calculated and the indicator becomes irrelevant. Many cars are loaded through the liquid line with vapors returned via the vapor line. In either case loading is typically by meter.

Mac McCulloch

Former Bureau of Explosives Inspector

[BEAUSABRE]

Lithonia Operator

Why do some large modern tank cars have a dip in the center, like the one on this page? (Scroll down a little, see the first tank car photo.) Also, on such cars is the bottom of the tank also not straight? That's hard to tell in photos. If the bottom of the tank is parallel to the top, and juts down a bit, with the center as its lowest point, my best guess is that makes the liquid flow better to the outlet, which I would assume is right at that low point. Yes? No?

That's because the tank car is unloaded from the bottom through a drain valve (and may have a viscous cargo), by sloping the tank, you put gravity to use helping you thoroughly drain the tank. The reason the top of the tank is sloped is that it is easier to build a cylinder and slope it than not - although there are cars with straight tops and sloping bottoms. It's really a matter of what is convenient to the builder.