Venting a trailer

In a vapor recovery system the tanks are sealed at all times. That means when you're unloading the vapors are being pushed from the storage tank into the truck tank. If you are loading then the vapors are pushed out of the truck tank back into the tank farm or wherever you load from. That's the point of vapor recovery. Companies like to insure that this system works all the time so they will spec. the truck or the trailer to have the brakes come on when you open the vapor recovery. Most of the time they do this by a flapper valve located on the piping of the vapor recovery end so when you hook up the vapor hose it pushes in the valve and locks the brakes. Any gasoline hauler should know this. If they are venting their tank it's not only dangerous but against the law. Vapor recovery prevents any outside air into the tank. With gasoline it's done for EPA reasons and fire reasons. For other chemicals I would not know unless I looked in the books. It could be for safety reasons because if anyone gets a good inhalation dose they drop over dead. So your answer is you do not vent your tanks unless done the right way. Now I have time to time been ask to vent my tank because it's got to go in the shop. Without anyone knowing I open all the domes and down the highway I go.

 

I've never once hooked up a vapor recovery line. Every time that has been needed it's been a customer unload. I'd bet yours will be too. Besides, if you need to do it then the company should train you.

 

When you get to the consignee, ask if they will be pushing it off with air or nitrogen. If not, then just open the vapor recovery valve and let it serve as a vent.

 

It all depends on the trailer. On most of the "center load" trailers the vent is the same pipe that your fitting sits on that you use when pressure off-loading. Sometimes it sits on the dome, others it's a stand-alone. Just remove the fitting or if it is permanently attached, remove your hose then open your hydro valve.

 

NaHS smells like rotten eggs, hence not wanting to open the dome. I know we (Superior) have it listed as a no touch/can haul which basically means the customer is required to unload when we haul loads of it, so I would say there is a good chance you can just kick back and relax at your delivery.

Side note, one of the ways they get that stuff is as a byproduct of refining gasoline. Somehow or another it separates out and the gas floats on top of it. I picked up a load at a small refinery in Kentucky once and the loader had to pay close attention to the storage tank level so he didn't begin pumping gas into my trailer.

 

It's all done by heat. The hotter the product the greater separation. Or close to it. The end product is light and can be mixed to form many other products. You heat it slightly and you'll have what we called in the navy "bunker" fuel. Heavy, messy, and very dirty to burn or anything else. Along the way you get basic gasoline which they take and do some cracking and other things to meet EPA standards. Just think it as a standing pipe. Going up the line the hotter it gets. Sealed at the bottom and many pipes coming out going up. As the temperature goes up the crude oil boils and you drain off what you need according to temperature. Gasoline is the main product and everything else is a plus nowadays. Years ago they burned off many dollars not knowing how or what to refine. A barrel of crude is 42 gallons and out of that barrel 20% is gasoline. That's the highest percentage of any product. The hotter the batch the lighter the product. Gasoline is towards the bottom BTW, H2S (Hydrogen Sulfide) can smell like rotten eggs also and if you get a big whiff of that stuff you're dead before you hit the floor.