API MPMS 6.3:1994 pdf download.Manual of Petroleum Measurement Standards Chapter 6—Metering Assemblies
6.3.6 Submersible Pump System
In a submersible pump system, the pump is located at the bottom of the fuel reservoir, and it pushes the fuel under pres- sure through the complete system. A single submersible pump may serve one or several dispensing hoses simultaneously. An important advantage of this system is that during op- eration, fuel is under pressure and little possibility exists for the fuel to vaporize and have an adverse effect on measure- ment accuracy. Once the piping system is purged, the sub- merged pump cannot pump air into the system. A check valve at the pump discharge head prevents backflow in the piping when the system is inoperative. If backflow or emp- tying does occur—allowing air to enter the pipe connecting the pump to the pump discharge head—the air will be purged from the pipe when the pump is activated for subsequent dis- pensing and the pipe is repressurized with fuel. Since submersible pump systems are pressurized, a means for detecting leaks in the piping is usually provided. The sys- tems also include an impact safety valve beneath each dis- penser to stop the flow of fuel if a dispenser is struck or damaged. Pressure from thermal expansion is relieved through a thermal relief valve in or near the check valve in the pump discharge head. Figure 1 illustrates a typical submersible pump system.
6.3.7 Self-Contained-Pump System
A self-contained-pump system is a dispensing system whose dispenser contains the pump that draws its fuel. In this system, fuel is drawn from the fuel reservoir up through piping to the pump within the island dispenser. From that point on, the pump pushes the fuel through the balance of the system. In this system—unlike a submersible pump sys- tem—no dispenser impact valve is utilized in suction piping since a break usually terminates fuel flow. Although self- contained-pump systems are less costly in certain applica- tions, they tend to vaporize fuel as it is sucked upwards by the pump from underground storage. Note: Caution must be exercised not to exceed the manufacturer’s recom- mendations for vertical lift and overall horizontal length of piping during in- stallation and application. Otherwise, an operational problem might follow.
API MPMS 6.3:1994 pdf download
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