order to ensure proper operation of the Hydra-Brake®, a constant
pressure supply source must be used. Some methods for obtaining this
simple method is to use an open tank mounted at sufficient height to
provide ample pressure to the brake. A liquid level control and an
overflow pipe should be incorporated in this tank.
sufficient height is not available a centrifugal pump may be used to
supply the brake. The pump suction line should be immersed in the
tank or reservoir of constant level. An air chamber should be used on
the discharge line as close as possible to the pump.
pressure-regulating valve which is fed from a high-pressure system
may be used to supply water to the brake at reduced pressure. It is
recommended that a surge chamber is installed after the valve to
dampen out any flow pulsation.
rare instances, the plant water supply system may be satisfactory
without further regulation.
more than one brake is to be fed from a constant pressure supply
source a manifold may be used. However, the supply line and manifold
should be oversized that changing the flow to one or more brakes does
not require readjustment of the other brakes on the line.
hand valves should be properly sized V ported or equivalent with such
construction that there is no movement of the valve plug with respect
to the valve seat once set in a given position. When sizing inlet
valves assume the pressure at the inlet to the brake is approximately
10 psi. The discharge pressure of the brakes varies with size, power
absorbed, and speed. It is for these reasons that definite sizing
information is not available. In the past, when actual test data has
been lacking, we assumed a discharge pressure of 10 psi for low speed
and power and 30 psi for high speed and power.
valves may be used for remote or controller actuation. It is
recommended that these valves be initially oversized with reduced
ports used to suit actual requirements. Valves selected should be of
such design that there is no movement of the valve plug with respect
to the valve seat once set in a given position. Valves with any
backlash in actuating linkage should not be used. If possible, manual
inlet valves should be installed in the control room in lieu of
remote control valves.
flowmeter should be used in all installations and located in the
control room if possible. When measuring power by heat rejection to
water, a 600 mm scale should be used, for other installations, a 250
mm scale is satisfactory. Locate the flowmeter upstream of the inlet
valve to prevent air bubbles from forming in the meter. The maximum
supply pressure will be governed by the allowable pressure on the
flowmeter. When required, remote reading flowmeters may be used.
water compartment vent should be provided on all installations. When
measuring power by torque and speed, a vent to atmospheric drain with
a hose running downhill with no U-bends or traps should be used.
method for the above and the method to be followed on all other
installations is the use of a float or swing check valve mounted
above the brake. In any case, should the inlet pressure to the brake
fall much below atmospheric (say, 5" Hg vacuum), provide
additional venting by connecting check valves to the unused vent
ports if available, in one of the inlet ports if available, or in the
inlet lines as close to the brake as possible.
temperature pickup (e.g. thermocouple) on the inlet line is necessary
only when measuring power by heat rejection to water. A thermocouple
or equivalent should always be used on the discharge line. The
temperature sensing element should be corrosion-resistant to water.
High-accuracy thermometers may be used if the operator is to be
stationed at the text location. In all cases, the temperature-sensing
element should be located some distance from the brake in the center
of the water line.
Hydra-Brake® should be properly selected for the power and speed
range of the test. The brake will operate satisfactorily under ideal
conditions as low as 2% of rated power. However, it is generally our
recommendation that, should the power absorbed drop below 10% of
capacity, then discs should be removed to improve control of the
brake. Information on removal is given in the "Assembly and
flexible hose on the inlet and discharge connections to the brake
should be used for all installations.
frequent removal of the brake is anticipated, the use of quick
disconnect couplings on the inlet and discharge lines is suggested.