FUEL STORAGE TANK VENTILLATION

[roker]

HELLO,
WE HAVE A FUEL TANK WITH AN INTERNAL FLOATING ROOF AND A FIXED ROOF ABOVE, IN ORDER TO MAINTAIN ZERO EMISSION TO THE ATMOSPHERE CAN WE USE VACUUM BREAKERS FOR INBREATHING AND WHEN OUTBREATHING TO CONNECT THE OPENINIGS TO A HEADER TO A THERMAL OXIDIZER, I MEAN THAT WE WILL DIVIDE THE PERIPHERICAL OPENINGS IN THE FIXED ROOF FOR VACUUM BREAKERS AND FOR CONNECTION TO THE THERMAL OXIDIZER.
IS IT OK ACCORDING TO API 650 AND API 2000?

REGARDS,
ROKER

 

[EmmanuelTop]

Two systems with different design pressures should not be connected in such a way that the system with lower design pressure (e.g. storage tank) discharges to the system with higher design pressure (e.g. thermal oxidizer). There have been many occasions in which this configuration led to overpressure of the lower pressure system, with more or less severe consequences.





Dejan IVANOVIC
Process Engineer, MSChE

 

[bimr]

This vent scheme is common in tank farms.

Conservation vents, not vacuum breakers are used. Consider the use of a 2nd vent (at higher pressure) to atmosphere to protect the tank

 

[LittleInch]

My reading of API 650, especially annex H H5.2.2.3 states if you have vents which admit air then these need to be circulation vents and if not then gas blanketing or other system used to prevent the development of a combustible gas mixture.

Your issue is almost certainly that the tank is only designed for "atmospheric" pressure which leaves very little available pressure (4 inches of water guage) to blow the vapour out to any equipment located some distance away. you can end up with massive ducts and if the oxidizer creates any sort of back pressure, your idea won't work I'm afraid.

So sounds like a good idea, but unless your tank is designed for a higher pressure, it is practically impossible.

So check API 650 and check the design limits of your tank. if you get this wrong you will destroy your tank very easily. Do nothing without getting this properly designed and approved by competent, experienced tank designers.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[don1980]

API 650 tanks are fragile vessels. As mentioned above, the vent can be routed to an oxidizer but the tank design pressure has to be high enough to provide the necessary driving force. The design pressure for this tank will be less than 2.5 psig. When the primary vent from a storage tank is routed to a closed system such as an oxidizer, it's very important to have an emergency vent that's routed to the atmosphere.

 

[poli60]

The configuration depicted by bimr is commonly used in asphalt/bitumen storage.
The vent outlets are collected to a thermal or catalytic combustor.