API PUBL 1645
Stage II Vapor Recovery System Operations & System Installation Costs
|Publication Date:||1 August 2002|
Stage II vapor recovery is a well-known air quality control measure that reduces ozone precursors from gasoline dispensing facilities (GDFs). As a result of its relative high-visual profile, Stage II vapor controls are sometimes proposed as a part of a regional air quality attainment strategy without adequately comparing its overall cost effectiveness to other available control measures. Changes in equipment technology and system testing techniques continue to raise new issues associated with installing, operating and maintaining compliance of Stage II systems.
The purpose of this Stage II costs study partially comes from the U.S. EPA's more stringent ozone standard that will bring additional metropolitan areas into non-attainment status. These additional metropolitan non-attainment areas may consider Stage II controls as a priority air quality control measure. As a further consideration, the U.S. EPA has also implemented an on-board refueling vapor recovery (ORVR) requirement for new vehicles. It is designed to capture gasoline vapors at the nozzle/vehicle gas tank interface during refueling.
Adding to the complexity of the matter, the California Air Resources Board (CARB), a
This study considered three different types of retail gasoline outlet (RGO) vapor recovery systems:
1. vapor balance,
2. passive vacuum assist,
3. and active vacuum assist.
The "vapor balance" system, configured with a corrugated bellows over the nozzle spout designed for capturing vapor, has been in use since vapor recovery was first required. The system has been refined and upgraded with improving technology.
A more recent technology initially pioneered in the Midwest is the "passive vacuum assist" system. Initial versions of this system used reciprocal vacuum pumps for each active nozzle powered by the flow of gasoline to the vehicle fuel tank. Subsequent versions of this type of "dispenser-based" approach use electrical pumps to return the collected vapor back to the gasoline storage tanks, using electronic signals from the dispenser meters to regulate the vapor pump speed.
Finally, the "active vacuum assist" system has also under-gone many improvements since it was first used. This system maintains a vacuum on the entire Stage II recovery system and processes the excess vapor collected through a central vapor processor or burner.
A survey of API members and several other sources of information produced average Stage II installation cost data representing company-specific typical Stage II system configurations for the three targeted vapor recovery system types. The collected data was adjusted to conform to a consistent refueling system configuration that should not be considered typical for the industry. The equipment configuration used in this paper were an equalized number of nozzles, hoses, dispensers and refueling positions for all three types of vapor recovery systems evaluated. [See Table 1.]