SOP on Cleaning and Replacement of Filters

Rahul Kashyap

To describe the procedure for cleaning and replacement of filters.
  • Switch off the power supply of the machine.
  • Put up board “Man at work, do not switch ON”.
  • Open the door of the machine and removes the filters from filter housing.
  • Keep the dusty filters in a Poly-bag.
  • Take the dusty filter in designated filter cleaning area.
  • Take out the filter from poly-bag and wash it with Purified water and then with air. Water Pressure should not be more than 2.0 kg/cm2.
  • After washing the filter, remove its water by applying air in opposite direction and keep it on the racks for complete drying. Air Pressure should not be more than 2.0 kg/cm2.
  • Check for any damage of filter physically and if filter found damage, change it with a new filter.
  • Cover the clean filter in a poly-bag.
  • Clean the filter housing with vacuum cleaner and duster.
  • Fit the filter in its place and ensure that there should be no gap around filter and filter housing.
  • Cleaning of Return riser filters and RLAF filters (pre & fine filters) are in concerned department scope.
  • If any filter found damage concerned department will raise a work order to replace damage filter as per SOP Break down maintenance procedure
  • Cleaning activities of all filters will be carried out as per Annual Master Filter Cleaning
  • All concerned shall record all activity of cleaning and replacement record
  • After cleaning of riser filter update the status of cleaning on label as per QA SOP of Procedure for status labelling

 Frequency of Cleaning of Filters
            Pre-Filter                       Weekly±2 Days or DP indication
            Pre-Filter                       Weekly±2 Days or DP indication
            Fresh Air filter               Weekly±2 Days
            Fine Filter                     15 ±2 Days or DP indication
            RLAF Pre filter              Weekly±2 Days/ DP Alarming or during product change over
            RLAF Fine filter            15±2 Days or DP Alarming
            Return Riser Filter        Weekly±2 Days or during product change over
Frequency of Replacement of Filters
            Fresh Air Filter                            After every 2 years ± 15 days
            Pre-filter (5 µ)                             After every 2 years ± 15 days
            Fine filter (3 µ)                            After every 2 years ± 15 days
HEPA Filter (0.3 µ)                    After every 4 years ± 15 days
(Note: - if any filter found damaged it can be replaced immediately)
Repairing and Replacement of HEPA Filters:
If side leakages are observed between filter and housing, then replace the gasket and seal the gap with silicon sealant. 
Acceptance Limit: During filter integrity if the downstream leakage exceeds 0.01 % from the gasket, change the gasket. After rectification of the leakage if the leakage does not fall within 0.01 %, replace the HEPA filter with new one.
  • If HEPA filter need to replace, switch off the AHU, close the supply damper, close the fresh air damper and open the HEPA filter from filter housing. Clean the housing area and put the new HEPA filter in housing. Fill silicon sealant in the edges and corners of filter housing and terminal box and tight all the bolts. Check the HEPA filter integrity and if the filter passes in integrity, open the supply and fresh air damper. Run the system for at least 30 minutes. Check the particle count in respective area. If particle count of area is under limit of respective class, then hand over the area for Fumigation and Microbial Count Test.

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