Flow Control Technology for Oil Delivery

Fuel oil suppliers, whether delivering heating oil to homes or diesel fuel to commercial fleets, need delivery nozzles that they can rely on to control th e flow and prevent spills and drips.

Fuel oil suppliers, whether delivering heating oil to homes or diesel fuel to commercial fleets, need delivery nozzles that they can rely on to control the flow and prevent spills and drips. Operating efficiency and reliability are also extremely important.

For more than 30 years now, devices such as the “ball nozzle” and the flow-switch/ angle-check valve have served these needs and continue to be fuel oil companies’ best assets for environmentally safe and efficient customer service.

When it comes to home heating oil delivery, smaller nozzles are used, whereas larger nozzles are used for commercial fleet fueling needs. In either case, the question is: how do you regulate the flow? The answer involves an automatic system using the ball nozzle and a flow switch in the truck.

Figure 1: Ball Valve

The ball nozzle
The ball nozzle has a less-restrictive flow than other types of nozzles; but, at the same time, it has many settings from “closed” to “full open.” This range of settings allows for the occasional slow fill, which can be used to lessen foaming. Foaming, when left unchecked, reduces the amount of fuel delivered, just as foam poured into a glass limits the volume of liquid that can be poured into it.

With the ball nozzle, hydraulic shock is minimized since the opening and closing of the nozzle is always under the control of the operator regardless of system pressure. When unchecked, hydraulic shock travels back through the hose to the pump and can damage the pump and other components on the delivery truck. An anti-drain valve eliminates any nozzle drip.

To meet the reliability and efficiency criteria, nozzles need to be durable and easy to maintain. They also need to be designed to eliminate kinking hoses. Both the smaller and larger ball nozzles have a compact, rugged design. They are made of brass, aluminum and Teflon, and are designed for quick and easy replacement of parts. A swivel under pressure aids in positioning the nozzle and keeps the hose from kinking.

Efficiency is also enhanced by the multi-purpose nozzle’s connector adapter. It can be used as a wrench to open and close the all-weather caps at fueling sites, and it serves as a tight leak proof connection as well (see Figure 1).

Automatic control system
The automatic flow control system uses a flow switch to monitor the flow of product through the delivery truck’s discharge pipe. The flow switch, in turn, controls a throttle actuator that advances the truck engine throttle to a pre-set speed when the flow begins.

With an automatic system, the truck engine is left idling until the driver opens the nozzle to begin delivery (see Figure 2). The initial flow (“idle pumping rate”) operates the flow switch that triggers the throttle actuator and increases the truck engine’s speed to a pre-set pumping rate for the balance of the delivery. When the driver closes the nozzle, the flow switch senses the cessation of the flow and releases the throttle actuator, thus returning the engine to idle speed. Action is nearly instantaneous; the truck’s engine “revs up” as soon as the nozzle is opened and returns to idle as soon as the nozzle is closed.

Figure 2: Flow Control Diagram

The flow switch looks somewhat like (and contains) an angle check valve. A discharge line check valve is generally required on fuel trucks by weights-and-measures ordinances to prevent product from flowing back through the delivery meter when the hose is rewound. The flow switch contains a built-in hose pressure bleed valve. This valve permits high pumping pressure, trapped in the hose at the nozzle shutoff, to bleed back slowly through the check valve until the hose pressure drops to 25 psi and the relief valve closes to hold this pressure in the hose during rewind. This relief valve may be blocked out at installation if not permitted by local regulations.

By using the flow switch /angle check valve for automatic flow control, the pumping rate is controlled from the nozzle. This reduces wear and tear on the hose, pump and engine.

The flow switch and check valve are combined into one unit. The unit is available with air or an electric switch and furnished with NPT (national pipe thread) or BSP (British standard pipe) threading as well as a hose pressure bleed valve.

The flow switch/angle check valve controls the truck engine speed; the valve is used with centrifugal and positive displacement pumps. Auxiliary bypass valves with positive displacement pumps reduce the pressure at idle speed, which increases the flexibility of the hose. The hose is locked during pumping and while driving to prevent hose reel movement.

The flow switch/angle check valve has interlocking air emergency brakes. A great deal that can be said for “tried and true” technology that works well and can be depended on. Scully’s automatic control system fits in this category.

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