TANK LIFTING TECHNOLOGY
Leaking tank bottoms,
spillage and pollution
are serious hazards for
tank farm operators and the
environment. Strict
regulations and high incident
costs impel tank farm owners
to have tank bottoms and
foundations inspected,
maintained and repaired (or
even replaced) on a regular
basis, in order to prevent
leaks and pollution. They may
also opt for the installation of
a secondary containment
device beneath the tanks,
such as membranes or liners.
But before any of these
measures can be taken, the
tank must be lifted in order
to provide access to its
bottom and foundation, and
choosing the right equipment
for the job will ensure the
project runs smoothly and
safely.
Hydraulic step jacks
Using high-pressure hydraulic
step jacks in serial connection,
simultaneously operated by
one large pump, storage tanks
can be gradually lifted while
maintaining their balance. The
step jacks are installed 'upside
down', which means that the
plunger moves downward
while the tank is pushed in an
upward direction. This
movement creates space
under the so called step plate,
at both sides of the plunger,
where wooden beams - as
part of a much larger
construction - are placed to
support the load. After that,
the plunger is retracted in an
upwards direction to make
room for another set of beams
in the centre, against which
the jack can push itself off
during its next lifting step. The
second layer of wooden beams
is position on the first layer at
a 90° angle, so as to build a
firm support structure (see
Figure 1). The procedure
described is repeated several
times, until there is enough
room between the tank
bottom and foundation to
carry out repairs and
maintenance, or to install a
secondary containment
device.
