Barrier cars for hazardous loads

[PhilM]

I assume that there is a requirement in the US for barrier cars between locomotives and hazardous loads - there often seems to be a ratty covered hoper in front of tank cars. Does anyone know the rules? I cant seem to find anything on google but I might be using the wrong terminology!

[doctor quinn]

Try looking for “buffer car” that should give better results 

 

http://cs.trains.com/trn/f/111/t/227069.aspx

[PhilM]

Thanks Doc!

 

[dave1905]

Worked for a railroad for 37 years.  Generally a loaded tank car with a hazardous placard must be no closer than the 6th car from the engine or occupied caboose.  If train length doesn't permit that, it must be no closer than the second car from the engine or caboose.

 

What "train length permitting" means is that if the train doesn't have enough cars in the consist that would qualify as cover cars.

 

The dedicated "barrier car", called a buffer car or cover car in the US, are only used on unit hazmat trains,  because the train is entirely loaded hazmat tanks, so there aren't naturally any cars that can be used as cover.  The railroad still has to comply with the train placement rules, so they add a dedicated "buffer" car to the train to use as cover (often 2 buffers, one on each end.)  On a regular,  general freight train, the railroad would just use other cars in the train that qualify as buffer/cover cars, which means there would be 5 cover cars, but they would not be "dedicated" buffer cars.  Eligible cars could be any car of any type, loaded or empty, that is not another placarded hazmat load, isn't a shiftable load and isn't a running mechanical reefer (simplified list).

 

There is no requirement that the buffer car be a load or a specific car type.  Often its a different type of car than a tank, just to make it more visible to keep track of and it will be loaded with sand or some inert material for train handling purposes, having an empty car ahead of 100 loaded cars is a train derailment risk.

 

Here is a link to a handout for a clinic I gave on the OpSig Virtual Meet about pre-1977 hazmat rules.

 

Hazmat Presentation - pdf (wnbranch.com)

Edited February 24, 2021 by dave1905

[jasond]

Excellent stuff Dave, presumably the frequency of the dangerous load movements determine where the buffer cars are likely to be kept. 

 

It's interesting how much we can learn by chance.  For some reason, I was watching a film reviewing explosives the other day (!?) and, have you noticed that when there's  a big bang: bits and pieces flying out, flash/fire/smoke, there's often a spherical cloud of water droplets expanding out at the same time.  Water...? 

 

I've always wondered why we see it, steam is colourless.  Apparently it's the shock wave from the explosion compressing any otherwise unnoticeable water vapour in the air into droplets.  Hmmm, must go and boil a kettle now.

Jason

[dave1905]

4 hours ago, jasond said:

Excellent stuff Dave, presumably the frequency of the dangerous load movements determine where the buffer cars are likely to be kept. 

 

They don't "keep" buffer cars anyplace.  They stay with the train.  They are unit trains.  The  buffer cars will either be at the origin shipper, at the destination consignee or on the train in between.

 

For the 10's of thousands of hazmat shipments that travel in regular freight trains there are no assigned buffer cars.  They just use the other cars in the train.  The northward trains off the Gulf coast are probably 25-50% chemical shipments and none of them have assigned buffer cars, they just cover the hazmat with whatever is available in the train.

 

Quote

 

It's interesting how much we can learn by chance.  For some reason, I was watching a film reviewing explosives the other day (!?) and, have you noticed that when there's  a big bang: bits and pieces flying out, flash/fire/smoke, there's often a spherical cloud of water droplets expanding out at the same time.  Water...? 

I've always wondered why we see it, steam is colourless.  Apparently it's the shock wave from the explosion compressing any otherwise unnoticeable water vapour in the air into droplets.  Hmmm, must go and boil a kettle now.

 

 

 

The shock wave is a pressure wave in the air.  As the air compresses then decompresses teh action causes the water vapor in the air to condense into visible droplets then the air pressure normalizes the droplets evaporate.  Yo can see the same thing in a shock wave following a high speed jet, or when an aircraft makes a sharp turn there will be contrail off a wing tip.  

[PhilM]

Really informative Dave - thanks. Does it  mean that you cant switch a single (or small number of) hazmat cars without using a handy "safe" car as a buffer? That adds a bit more interest to switching operations.

[pH]

4 minutes ago, PhilM said:

Really informative Dave - thanks. Does it  mean that you cant switch a single (or small number of) hazmat cars without using a handy "safe" car as a buffer? That adds a bit more interest to switching operations.

I don’t know about the US, but in Canada it would appear switching and perhaps trip workings don’t need barrier cars. There are CPR trip workings around here from a petroleum storage facility and I have never seen a barrier car in these trains. Trains are maybe 10-12 tank cars, no caboose.

 

Here’s a train from the storage facility - no barrier car behind the units:

 

[dave1905]

Are the tank cars placarded and what is the placard?  You don't need cover for tank cars, you don't necessarily need cover when switching, you need cover for hazardous loads in a train.

9 hours ago, PhilM said:

Really informative Dave - thanks. Does it  mean that you cant switch a single (or small number of) hazmat cars without using a handy "safe" car as a buffer? That adds a bit more interest to switching operations.

Depends on the placard.  Some cars need cover when being switched, other cars do not.  If you need cover then any non-placarded, non shiftable load car can be used.

[Talltim]

Something I found odd is that some of the DOD flatcars are marked as barrier/buffer cars. I get that they might need buffers cars, but why limit which cars they use (both for loads and for buffers)? 

[dave1905]

So the people loading cars don't load them by accident.  I assume they are for handling nuclear cask cars..