are flushed so as to prevent the possible
chemical effect of the process fluid on the
equipment or its parts. Chemical corrosion
is the typical attack normally encountered
on the seal material in use in pumps. Also,
most flush material is either liquid paraffin
or hydrocarbon of low viscosity selectively
designed to give a clean clear wash. This
discussion shall base on the paraffin flush
filters. A typical example could be found in
use on acid pumps.
F ilter commissioning
1. Confirm that the filter is in good working
condition.
2. Ensure that the flush materials is
available and on line to the filter.
3. Line up the filter unit to be in service by
diverting the flow line through the desired
filter. Filter can be lined up in series or in
parallel depending on the efficiency and
operational provision.
4. Check and ensure that the filter
differential pressure gauge tapped
between it two ends is in place and in
good working condition.
Filter differential is the parameter that
describes the status of the filter at all times.
In some instance concentration change,
increase in the thickness of cake deposit or
even the conductive properties of filtrates
are used as the driving force across filters.
5. Commission the filter by lining the
isolation valves between the filter. Flush
filter downstream valve is to be initially
lined up before the upstream valve so as
to prevent the septum from damage due
to pressure build up. Therefore during
shutdown the reverse is the case.
6. Confirm that the operating pressures
as well as the differential pressure are
normal.
D iverting filter flow
Considering the lube oil and flush filter.
In such filter where provision is made for
diversion due poor filter performance
operators need to divert the process flow
through the standby filter.
1. Line up the downstream valve of the
standby filter to be commissioned.
2. Close the upstream valve of the filter in
service and line up the upstream valve of
the standby filter simultaneously.
3. Close the downstream valve of the
filter initially in service when its pressure
dropped. Then completely isolated it by
double blocking its isolation valve.
The above causes are mostly applicable
to flush filters. Lube oil filters are provided
with diversion arms that direct the
settings of the flow through the filters.
The arm is normally in the form of a
handy valve built for that purpose. It is
simply turned as described by design
and labeled thereby. Operators should
therefore be familiar with the diversion
techniques labeled by the vendor.
P reparing filters for
maintenance
This shall be based on the maintenance
procedure on the process filter e.g. rotary
vacuum filters, sand filters and to some
extent clay treaters. These are process
equipment used directly in line unlike
flush oil and air filter used on process
utilities.