Over many years, simple gear pumps have shown they can be the component of choice to power a broad range of hydraulic applications. Yet their close cousins, rotary flow dividers, may be the most underused of fluid power components.

The rotary flow divider consists of a series of positivedisplacement gear motor sections interconnected by a common shaft within a body that has internal flow passages to connect the inlet and outlet ports. Flow enters a common inlet and is divided into two or more separate outlet flows. These outlet flows may be equal or proportional — depending on the relationship of the gear widths of the individual sections.

Fluid from a prime source — typically a pump — provides motive power to rotate the flow divider. Although the flow divider adds no energy to the fluid, each outlet can perform at an energy level different from the others. Flow dividers operate on the principle that fluid horsepower input equals fluid horsepower output, less the unit's inefficiency. Flow dividers are used to distribute pump flow, to synchronize the operation of multiple cylinders or motors, and to intensify or reduce the pressure in secondary circuits. Their use most often eliminates the high costs of multiple pumps and the problems common in feeding them.

Assume an ideal two-section rotary flow divider in which both gear widths are the same. If both downstream loads are the same, the unit will split its input flow approximately in half, with the output flows approximately equal. On the other hand, if one output flow is connected to a load and the other is piped to tank with no load, the low-pressure section will act as a motor. Its energy will be transferred through the shaft to the loaded section. More fluid will flow to the reservoir while the other branch will operate at higher pressure.

The illustrated rotary flow divider operates most efficiently at 700 to 1300 rpm (above 1300 rpm, excessive noise may occur). Units are available in two to five sections with gear widths from 1/2 to 3 in. (Note that narrow gear widths are less efficient.) One series of flow dividers is rated at 3500 psi; a second is rated at 4000 psi.