NGL pressurized tank loading

Hello all,

I have been desperately looking for information regarding pressurized loading of NGL's/Condensate and can't find the required information. I am hoping someone can help help me out a little.

I need to estimate the amount of hydrocarbon vapor that escapes to the atmosphere during pressurized loading of hydrocarbon liquids. I know that there is a vapor balance system that transfers any displaced volume in the tanker to the storage tank but what happens to gasses and liquids remaining in the hoses after the transfer is complete.

For instance if NGLs stored at 200 psi are transferred to a tanker what happens to the liquid/vapor in the transfer hose that is at 200 psi. I know at the very least that the pressure would have to be released slowly from the hose but what happens to those vapors? are they vented to the atmosphere? Does the transfer hose remain sealed (valve closed) so that the liquid/vapors remain in the hose?

any information regarding the procedure used for loading these liquids would be greatly appreciated. cheers