Number of Tanks Gasoline Can be dropped into with Stage I Manifold

[jd2env]

Is any one aware of a guidance document or regulatory requirement that limits the number of tanks that product can be drop into when the Stage I Vapor Recovery is manifolded between the tanks and only one dry break is being used?

[ZMiller]

One tank at a time or a drop rate in total up to 400 gallons per minute.

As per C.A.R.B.

DESIGN CRITERIA
STAGE I VAPOR CONTROL SYSTEMS
GASOLINE SERVICE STATIONS

[ZMiller]

Good question regarding Stage I vapor recovery loading in and or out of dynamic balance. About time someone asked.

What happens when the drop rate is exceeded?
1. Dynamic over back pressure builds in tank receiving fuel and vents through pressure/vacuum valve on riser and sub grade tank top fittings to surrounding atmospheres.

What happens when the vapor flow rate escaping through the tank vent risers pressure vacuum valve exceeds 6,500 CFH?
2. Dynamic over back pressure continues to build and will damage tank and associated fueling system components.

It's not uncommon to see 800 gallons per minute being dropped in stations these days.

3. 810 gallons per minute would typically void equipment warranties and likely, over time have fatal effects on tank containment boundaries, tank compartment bulkheads, tank top fittings, vent piping and associated sump component integrity.

One does have to wonder why vapors are showing up in sumps. Now you know.

API 520 Critical Pressure Relief Header Back Pressure Calculation?

[ZMiller]

Just letting city dwellers know they can breath easy.

Calculated volume emissions of pollutants exhausting into surrounding environments from the average gasoline fueling station during a bulk fueling delivery is typically 9.8 tons per year. Benzene, Xylene and Toluene being the most harmful components of the gasoline vapor.