HPCF Fuller Earth Filter Charging

Purpose of Fuller Earth Filter:
Control fluid is used for 500 MW Turbine governing system. For smooth and trouble free
operation of turbine control valves in all conditions, chemical and mechanical properties of
control fluid is maintained always. Acidity of Control Fluid is to be maintained maximum of
0.1mg of KOH/gm of oil. To maintain this acidity, CF regeneration pump circulates oil through
fuller earth filter.Fuller Earth Filters are used for removal of acids and soluble surface acting
contaminants by adsorption. CF regeneration pump should run on continuous basis even if
Control fluid pump is in stopped condition & its heater should ON/OFF on interlock.

Control Fluid System consists of three numbers of filters:
a) Dry Filter: It will remove dirt & water from filter.
b) Fuller Earth Filter: It is used for neutralization of acidity.
c) Fine Filter: It retains the finest particle of the dirt , both metallic & non-metallic impurities.

Procedure of Isolation of Fuller Earth Filter:
Isolation of fuller earth is required whenever FRF acidity exceeds maximum permissible limit for replacement of filter OR Contamination of the Filter (Filter DP High).Following procedure is to be followed for isolation of filters.
 Open common bypass valve of all filters going to CF tank.
 Isolate all filters by closing inlet and outlet valves.
 Drain individual filters by opening drain line. All drain lines will go to DPT.
 Line up of Suction of CF regeneration pump to be changed to DPT from CF tank , for
transfer of oil to CF tank.
 Observe rise in CF tank level during transfer of oil from DPT.
 After Complete draining of Filter , PTW to be issued to Turbine Maintenance.