Where do the vapors go?

I've been learning about tankers and learned that when unloading fuel, there's another hose that directs the fumes from the in-ground tank back into the tanker. So once the process is done, where does the driver unload the vapors?

 

The vapors go back through the vapor recovery header, driven by the pressure of the gasoline being bottom loaded.

A hose at the loading rack is hooked to one of the vapor header outlets (usually the rearmost one) and directs the vapors to the flare stack, where they are burned off.

 

Depends on what you are doing. If you unloading vapor goes from storage tank to trailer tank. If you are loading vapors going back to storage.

 

Some loading racks have a VRU (vapor recovery unit), but many still send the vapors directly to the combustor.

 

Petroleum units with vapor recovery are not vented to the atmosphere. Everything is a closed loop to prevent pollution from vapor emissions since the early 70's. which is also when the stopped top-loading gasoline with a 'spiller' into the manhole. Each compartment was equipped with a vapor outlet in sync with the discharge outlet and a overflow protection float and a special bottom loading adapter.

Bottom loading increased the flow rate 2x or 3x VRS using a spiller making it quicker to load.

Discharge is the opposite, instead of the old atmospheric vent pipes, the storage tank has a double connection for liquid in and vapor out and the connection has two hoses allowing the gas to flow in as the vapor replaces it in the tank preventing a vacuum.

 

Where do you unload using a vapor recovery system?
I do aviation fuels, no recovery used. I see gas stations and truck stops don’t use it either.
Only place we use it is at the loading rack.

 

every gas station in NJ since 1978

 

I see fuel haulers unloading with only one hose. So the vacuum created while unloading the trailer sucks fresh air into the trailer. At least that is how I would assume it works.

 

That’s it. Open a vapor recovery fitting and let the air suck in while it unload to keep the compartment from collapsing.

 

Some gas stations have em. Depends when they were built. I deliver gas to one station that doesn’t have them. They are building a new station a hundred yards to the west. It will have em. The old station will be town down. Twice the work. Two hoses for every tank.