In service station environments, fuel is delivered to fuel dispensers from underground storage tanks (UST), sometimes referred to as fuel storage tanks. USTs are large containers located beneath the ground that contain fuel. A separate UST is provided for each fuel type, such as low octane gasoline, high-octane gasoline, and diesel fuel. In order to deliver the fuel from the USTs to the fuel dispensers, a submersible turbine pump (STP) is provided that pumps fuel out of the UST and delivers the fuel to fuel dispensers through a main fuel piping conduit that runs beneath the ground in the service station.
A typical STP has a casing body that includes a top, also called a “packer,” and a manifold. The packer fits on top of the manifold to form a tight seal when the STP is its normal configuration. If access to the internal chamber of the STP is required, the packer can be removed from the manifold. The STP also includes a check valve within a hydraulics cavity. As fuel is pumped into the STP, the fuel flow encounters the check valve, which allows fuel flow from an inlet side to an outlet side and prevents fuel from back flowing to the UST.
When the STP is serviced, the STP is shut off and the service personnel must remove the packer. However, after the STP is turned off, there is a differential pressure between the outlet side of the check valve and atmosphere. If the housing around the check valve is removed by service personnel to gain access to the check valve, the pressure build up on the outlet side of the check valve will equalize with atmosphere and fuel will possibly spill outside of the STP and onto the service personnel and/or the environment. Thus, there remains a need for the ability to depressurize the check valve before the check valve is serviced.
In addition, when testing the fuel supply piping for leaks, it is desirable to isolate the STP from the fuel supply piping. If a leak is detected after the STP is isolated from the fuel supply piping, then the STP can be eliminated as the source of the leak. Accordingly, there also remains a need for an STP that can easily be isolated from the fuel supply piping during testing.