Flow in Retail Fueling Systems

1. Flow in Retail Fueling Systems

2. Overview- Static Head in Flow Systems The Flow System - Resistance to Flow • Pump and Motor in the tank create pressure to overcome resistances to flow. The two types of resistances are “static head” and “dynamic head” Static Head • The effect of static head does not vary with the flow rate • The height that a fluid must be lifted. This is the distance from the product in the tank to the point of discharge into a car tank or loading rack discharge point. • In the submersible pumping system that distance is taken as the worst case scenario of a nearly empty tank • In bottom loading applications the highest point in the tanker is taken as the point of discharge. • The static head may vary with the tank level. The resulting variation can make a difference of 7- 11 ft, or about 2-3psi in the pressure of a pump.Usually the rest of the station configuration will keep the static head requirement constant.

3. The Flow System - Resistance to Flow Point of discharge Grade Rise Actual Static Head Bury Depth Worst case Static Head Static Head Static Head in a Retail Fueling System Static Head includes: • Product level to the packer, • Bury depth • rise in grade to the islands • Height to discharge point

4. The Flow System - Resistance to Flow Overview - Dynamic Head Resistance in Flow Systems Dynamic Head- What is Dynamic Head • Dynamic Head is resistance to the movement of product from the tank to the nozzle caused by fueling system components • This resistance varies with the flow rate of the product through the component. The higher the flow rate, the higher the resistance • The relationship between the pressure and resulting flow is exponential and not proportional. (twice the flow requires four times the pressure, not twice the pressure.) • The resistance profile of each component causes a decrease in head or pressure as fluid passes through that component. The pressure at the pump starts at a higher value and every component the product passes through decreases the pressure at that point until the pressure is “0” at the point of discharge. • Total system resistances vary depending on the total flow passing through the component. • Component resistances are additive and can be translated into a total pressure loss for the system. Klaus Review – Needs wordsmith

5. The Flow System - Resistance to Flow Overview - Dynamic Head Resistance in Flow Systems Dynamic Head Components That Create Dynamic Flow Resistance in a Retail Fueling System- Any component that has product flowing through it affects the total resistance or dynamic head of the system • Piping- • The trunk (closest piping to the submersible pump) has the highest flow rate • The branches have less flow through them (only those nozzles and dispensers on that line segment) • Flexible Connectors • Accessories: • Leak Detectors • Valves, such as check valves, ball valves • In-line filters and screens • Safety Valves • Dispensers and “Hanging Hardware” • Dispenser losses, including meter, filters • Nozzles • Hoses • Breakaway fittings • Swivels • Usually about 2/3 of the resistance at the dispenser area is due to hanging hardware. Klaus Review – Needs wordsmith

6. Dynamic Head Loss System Head Losses- Diagram • Causes of Dynamic Head Losses- At Higher Flow Parts of the System • Leak Detector • Valves • Piping Trunk • Piping Branches • Causes of Dynamic Head Losses- At Lower Flow Parts of the System • Dispenser, meter • Breakaway • Filter • Hose • Nozzle • Swivels Static Head Loss • Caused by the height a fluid must be lifted from tank to nozzle

7. Head Loss of 1 ½ vs. 2 in Pipe per 100 ft 85 ft head loss 60 GPM 12 ft head loss Dynamic Head Losses of Components • Notice that the head increases exponentially, not proportionally. Increasing the pressure by a factor of 4 only increases the flow by a factor of 2. This is true for all the components of the flow system that the product flows through. • Piping size is important in the areas of the piping system that have the potential to carry the highest flows—generally near the pump.

8. Pressure vs. Flow for Encore Vapor Vac Dispensers with Various Hanging Hardware Dynamic Head Losses of Components • 2/3 of the head loss at the island is due to “Hanging Hardware– nozzles, hoses breakaways Total Dispenser and Hanging Hardware head loss Dispenser Loss= about 1/3 of pressure loss Hanging hardware head loss= about 2/3 of pressure loss

9. 100 ft. 100 ft. 100 ft. Pressure & Head Relationship • Pumps will pump all fluids to a maximum height at no flow condition or at called dead head (in this example—100 ft.). • Depending on the fluid, even though the height a pump can push to is the same, the pressure at the pump is different. Heavier products, such as diesel will exhibit a higher pressure than lighter products such as gasoline. 43 P.S.I 31 P.S.I 37 P.S.I Water Gasoline Diesel

10. To convert the feet of head to pressure Divide 2.31 by S.G of the new fluid to get feet of product per PSI for that fluid Example Calculations: Calculate the feet of product that exert 1 psi pressure of static head: Divide 2.31 by S.G to get feet of product per PSI. Gasoline: 2.31 ft per psi / .71 s.g=. 3.25 ft per psi Diesel: 2.31 / .85 s.g.= 2.72 ft per psi (remember water has a specific gravity of 1) Calculate the fluid pressure from head curves: Divide ft head from curve by 2.31 and multiply times S.G: Gasoline: (100 ft. /2.31)X 0.71=30.7 PSI Diesel: (100 ft /2.31)X0.85=36.8 PSI Converting Feet Head to PSI : Pressure & Head Relationship • Specific Gravity (S.G): Density of a product relative to water. Numbers less than 1.0 are fluids lighter than water. Numbers over 1.0 are fluids heavier than water. • Water =1.0 • Diesel =.82- .87( use average of 0.85) • Gasoline= .71 • 2.31 Ft depth of water=1 PSI for a fluid with a S.G of 1.0 • Divide 2.31 by S.G of the new fluid to get feet of product per PSI for that fluid

11. The Flow System – Generating Flow Overview – Universal Motor and Pump (UMP) Motor Pump

12. The Flow System – Generating Flow Overview – Universal Motor and Pump (UMP) Motors • Motors can be fixed speed or variable speed and drive the pump section of a UMP. • Fixed speed XX HP motors run at 3450 rpm on 60 hz power and 2850 rpm on 50 hz power. Pumps attached to them have one fixed output curve. • Variable speed motors can be controlled to generate a constant pressure output on the pumps they are attached to. Pressure output varies with the desired output programmed into the controller. The higher the rpm of the motor, the higher the output pressure of the pump.

13. The Flow System – Generating Flow Overview – Universal Motor and Pump (UMP) Pumps • Centrifugal pumps create pressure by accelerating fluid from the center of a spinning impeller to the outer perimeter • They may have several stages, each of which imparts increasing pressure to the fluid being pumped comprising of the parts below. • Each stage typically has 3 parts: • Impeller- is spun by the motor. Product enters at the central “eye” and is accelerated to the perimeter – producing pressure • Diffuser- directs the fluid leaving the impeller to the center of the pump, into the eye of the next stage’s impeller. • Diffuser plate- With the diffuser, the diffuser plate encloses the impeller, forming one stage.

14. The Flow System – Generating Flow Fluid leaving the impeller into the diffuser Direction impeller is turning Overview – Universal Motor and Pump (UMP) • Impellers spins fluid outward, accelerating it and creating pressure • Diffusers redirect product to the eye of the next impeller • About 14-15 P.S.I. is created in each stage in 60 hz pumps and about 9-10 psi in 50 hz pumps

15. The Flow System – Generating Flow Vane width Overview – Universal Motor and Pump (UMP) Methods For Increasing Flow • Increase the speed – higher HP motor • Increase the diameter • Increase the vane width Methods for increasing the output pressure of an impeller or pump • Increase the speed – higher HP motor • Increase the diameter of the impeller • Additional stages add incremental output pressure to the pump Impeller Diameter

16. Pump performance curves typically show pressure in the form of “HEAD”on the left Y axis and flow rate on the X bottom axis. The head , or pressure on the Y axis represents the pressure at which the pump can deliver the flow rate on th X axis. STP - Pump Performance Curves

17. P150S1 Pump Curve 60 ft head 58 GPM STP - Pump Performance Curves • Example: Against a head (pressure) of 60 ft, a 1 ½ hp pump will deliver 58 gallons per minute • The pump cannot vary from this curve. When running, it supplies the flow it can against the pressure it experiences in the flow system

18. STP - Pump Performance Curves • The pump cannot vary from the flow curve – • Changes in upstream components to reduce frictional pressure loss will improve overall system flow by reducing the amount of pressure the pump must overcome to deliver flow at the nozzle • As the pressure requirement decreases, the amount of flow a pump can deliver increases • The analogy is a garden hose that is throttled with a thumb. With a lot of pressure against the hose, there is very little flow. As the pressure against the hose is relaxed, the flow from the hose increases.

19. Constant output of chosen pressure Point at which pump cannot supply the required pressure STP - Pump Performance Curves • Variable speed pumps have multiple programmable set points for desired output pressure. • They will follow the chosen curve by slowing or speeding up the motor to react to the varying system flow resistances. • The pressure holds constant until the load is too great for the pump to maintain the pressure.

20. P150U1 and Manifolded P150U1 Pump Performance Single Pump Flow Manifolded Pump Flow STP - Pump Performance Curves • Manifolded Pump curves are Additive on the flow Axis (X axis) • Actual flow rate increase depends on the other system components • Adding manifolded pumps will not increase flow in an additive manner at the nozzle due to the pressure loss created by other system components 60 GPM @ 60 ft 120 GPM @ 60 ft

21. A= Static head B=Leak Detector loss C=Piping Loss D=Dispenser loss E= Hanging Hardware loss The equipment head losses are additive to make up a total system head loss curve. The Static and Dynamic Losses in the Pump Flow Program P150S1 with 8 nozzles running produces 68 GPM or 8.5 GPM per nozzle Combined head loss curve for 8 Nozzles operating E D C B 68 GPM A