Allied 300, Technical Manual, Page: 17 / 66

Allied Construction Products, LLC Technical Manual Ho-Pac 300, 300B & 500, 500B
6
4.3 Principle of Operation
The Allied Ho-Pac is a high-energy
compaction tool utilizing three compaction
techniques:
The Impulse Force generated by the
rotating eccentric mass vibrates the soil
near the base plate to eliminate voids
between material particles.
The Vibration Frequency of 2000
r.p.m. provides maximum effectiveness
for the consolidation and compaction of
granular soil materials.
The Down Force of the carrier provides
a preload force to effectively transfer the
vibrating energy and to compress the
material.
Optimum compaction is usually obtained
with two passes. The duration of the initial
pass is dependent on depth and material.
The second pass may require additional fill
material and Ho-Pac repositioning to
achieve a finished surface.
The Ho-Pac can also be an effective sheet
or pile driver. Vibration energy is transferred
through the sheet or pile to the soil. Soils
with 50% or more granular content are
“liquefied” by the vibration, which breaks the
skin friction, allowing the sheet or pile to
penetrate more easily. Refer to the
Compaction Manual for further details.
4.4 Definition of Hydraulic Installation
Terms
Hydraulic Flow
– A measure of the volume
of oil (values given in GPM / LPM)
necessary for the safe and efficient
operation of the Allied attachment. When
used in this application, the hydraulic motor
performs in a narrow flow range. For
attachments, such as the Ho-Pac, the ideal
speed of the motor is 2000 RPM. Not
enough flow will result in poor performance.
Too much flow can cause equipment
damage.
IMPORTANT
Never use a relief valve, as a means to
reduce the hydraulic oil flow to the Ho-Pac.
Oil by-passed over the relief valve will
cause significant heat generation and
result in damage to the equipment.
Operating Pressure
– A measure of the
hydraulic oil pressure (values given in PSI /
BAR) taken in the at
tachment’s supply line
during operation. For attachments such as
the Ho-Pac, the pressure value is
represented as a maximum value and a no
load value. While the Ho-Pac is operating,
the operating pressure will rise and fall as
conditions such as down pressure and soil
resistance change.
IMPORTANT
The Operating Pressure is not to be used
as a relief valve pressure setting. Poor
performance and significant heat
generation will occur.
Relief Valve
– An adjustable, spring-loaded
valve that opens when a preset pressure
value is reached. A relief valve is safety
device, used to protect the circuit against
hydraulic overload. Relief valves vary in
design. Pilot controlled pressure relief
valves are designed so that the relief
pressure increases very little as the flow
through the valve increases. For Ho-Pac
applications, they are recommended over
direct acting type relief valves.
IMPORTANT
The relief valve is a safety device, used to
protect the circuit against hydraulic
overload. It is a required component.
Dynamic Relief Pressure
–
Also referred
to as “Cracking Pressure”. The pressure
measured at the moment the oil pressure
exceeds the preset value of the relief valve
and the spool “cracks” open.