Power Packs are non-synchronized (non-unified™) pump systems, frequently called "common pressure" systems.
Equal pressure is applied to each outlet while the operator controls the FLOW of oil from
each outlet to each jacking point with a needle valve. The heaviest jacking point will require
more oil flow to raise as fast as the lighter jacking points.
The best way to raise a structure with a power pack is to jack on three points.
Think of picking up a flexible object like a shoe box. Pick it up with a finger in each corner and
the box will twist. If that was a building, the windows would shatter and the sheet rock would crack. But pick
the box up with two fingers under the left hand and one finger in the center of the right
hand and it doesn't
twist. Using this method to raise a building, it won't come up evenly but as long as it doesn't twist the building won't get damaged.
Jacks can be set at three points; one at the left rear, one at the left front and
two connected together at the right end to make up the three points. Raise the building
slowly, adjusting the needle valves to bring up each point as evenly as possible, stopping if
necessary to bring up the lowest point to match the other two points. If more jacks are needed,
tee the jacks in each point together to split the oil going to that point between the jacks in
that point or zone.
Power Packs are significantly less expensive than Unified™ Jacking machines
but require more experience and judgment in placement of the beams and jacks and more attention
from the operator during the jacking operation. With Unified™ Jacking machines, placement of the
beams and jacks is less critical because each point will come up at exactly the same rate
regardless of the weight on it and less attention is required from the operator, but the cost
is significantly more.
