Model 520 HT UCA
D01157216
Revision A, October 2015
25
operate. The pressure should be between 20 and 100 psig (1.4 and 6.8 bar) when
the pump is not in use. It is normal for the inlet air pressure to drop when the pump
is in operation. If the air pressure drops significantly and the pump seems unable to
achieve the desired pressure, it may be because the compressed air system is not
capable of delivering enough air to operate the pump.
The AIR TO PUMP regulator is used to control the air pressure to the air driven
hydraulic pump. Higher hydraulic pressures require higher air pressures. To adjust
the pressure of the air supplied to the pump, pull the knob on the regulator out to
unlock it. Turn the regulator knob clockwise to increase the pressure and
counterclockwise to decrease the pressure. When the adjustment is finished, push
the knob in to lock it in place.
If the PUMP AIR PRESSURE drops off significantly when the
pump is operating, an air line may be blocked or the compressor
may be insufficient to deliver the volume of air required.
This regulator is used to control the pressure of the air supplied to the pump. The
hydraulic pressure output of the pump is directly proportional to the air pressure
supplied to the pump. As the air pressure increases, the hydraulic pressures
increases and vice versa. Air pressure to the pump may be decreased by turning the
AIR TO PUMP regulator knob counterclockwise or increased by turning the knob
clockwise. If the regulator is set to a value and the pump switch is turned to the
ON position, the pump will increase pressure until the pneumatic force of the air
(air pressure multiplied by pneumatic piston area) equals the hydraulic force of the
pressurizing water (water pressure multiplied by pump piston area). At this point
the hydraulic and pneumatic pressures will be in equilibrium and the pump will
cease to stroke. If the water pressure falls for some reason, a force imbalance will
be created between the pneumatic and hydraulic sides of the pump and the pump
will begin to stroke and increase the hydraulic pressure until it is balanced with the
pneumatic pressure, then it will stop pumping. In this way, the pump may be used
as a pressure control device (combined with the relief valve) to establish the lower
pressure limit for a test.
6.3
Electrical Controls and Displays
The only front panel electrical controls are the POWER, and WATER SUPPLY
switches. These controls are discussed in detail below.
The switch labeled POWER controls electrical power to the entire instrument.
Nothing else is operable if this switch is not on. ..
The WATER SUPPLY switch supplies water to the UCA test cell, pump, and
cooling water. It should be in the ON position when the instrument is running.
