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SOP for Preventive Maintenance of AHU & Ventilation Units

Standard operating procedure for preventive maintenance of the air handling unit and ventilation units of pharmaceutical manufacturing facility.


The purpose of this SOP is to provide stepwise instructions for Preventive Maintenance of AHU & Ventilation units.


This procedure is applicable for Preventive Maintenance of AHU & Ventilation units.


Technicians are responsible to follow the laid down procedure in a sequential manner. Engineers are responsible to monitor closely and ensure that laid down procedure are followed. Finally, user department and QA should verify completion of Preventive Maintenance activity.


Head Engineering


5.1 Precaution

5.1.1 Disconnect the machine from electric supply mains.
5.1.2 Tag “Under preventive maintenance” board on it. While checking the direction of rotators of a motor one must remove the belts, so as to avoid damages to machine due to reverse rotation.
5.1.3 No tools & spanners should be left on the machine after carrying out preventive maintenance.
5.2 General assembly Frequency: Once in month ±7days
5.2.1 Switch ‘OFF’ the main supply and display the ‘UNDER PREVENTIVE MAINTENANCE’ board prominently on the front side of AHU.
5.2.2 Check all the nut & bolts of supply air filter plenum are properly fixed and tight.
Check that no gap between supply air filter frame and filter plenum, tighten up the bolts/replace the gasket if required.
5.2.3 Check manually all the duct joint of the supply and exhaust duct for air leakages & arrest them by tightening up the nut & bolts/or replace the gasket if required.
5.2.4 Check the door lock & door handle for any damage, replace or rectify it if found damaged
5.2.5 Check manually the door gasket for any air leakage if found replace the gasket.
5.2.6 Check if the nut & bolts / screw of HVAC & VU cabinet are properly fixed and tight.(If found loose, tighten it up by suitable tools or replace it, if required).
5.2.7 Check the air leakage from HVAC & VU cabinet; tighten up the nut/bolts if required.
5.2.8 Check the canvas connection of terminal branch / blower suction and discharge; replace it with a new one if found damaged.
5.2.9 Check the entire duct joint for Air leakage, arrest it by tightening up of nut bolts or replace the gasket if required.
5.2.10 Check the temperature of inlet / outlet of chilled water for its proper working.
5.2.11 Check the temperature of inlet / outlet of hot water for its proper working.
5.2.12 Check all the nuts and bolts of filters unit and tighten it up, if found loose and replace with new one, if it is found missing.
5.2.13 Check the air/dust leakage from filter unit and joint of if found, arrest it by tightening of nuts and bolts or replace the gaskets if required.
5.2.14 Check the canvas connection of blower suction/discharge side; if found damaged, replace it with a new one.

5.3 Electrical

5.3.1 Open the panel of the machine & clean it properly.
5.3.2 Tighten all the electrical connections, if found loose.
5.3.3 Clean the contacts of the contactor.
5.3.4 Check that the relay setting of the machine motor is at the rated maximum current of the motor.
5.3.5 Check the DOL reversible starter for proper reverse & forward direction of the motor, if not, rectify/replace it.
5.3.6 Dress all the cables / conduits in the panel & replace if required.
5.3.7 Switch ‘ON’ the main supply and check all sensors for its working.

5.4 Cooling Coil

5.4.1 Switch ‘OFF’ the main supply.
5.4.2 Open the doors of cooling coil section of the AHU.
5.4.3 Clean the surfaces of and cooling coil with the dry cloth.
5.4.4 Wash the inner surfaces of fins with the water.
5.4.5 Clean the drain of the AHU and inner surfaces of the AHU with the cloth.
5.4.6 Ensure that the water is not stagnant at the drain.
Note: Inform to production department before taking coil for cleaning

5.5 Motor

5.5.1 Ensure that the main power supply of the equipment is disconnected & all utilities are isolated.
5.5.2 Ensure that the machine is free of any dust on it.
5.5.3 Remove all the guards of the machine & remove the main motors.
5.5.4 Dismantle the motor.
5.5.5 Check the condition of the bearing & replace if required.
5.5.6 Check the winding insulation & if required same to be rectified.
5.5.7 Lubricate the bearings with AP-3 or its equivalent grease & assemble it on the shaft.
5.5.8 Reassemble the motor.

5.6 Blower

5.6.1 Remove the pulleys from its position.
5.6.2 Check the condition of the pulley / Key / Keyways & rectify / replace if required.
5.6.3 Check the condition of the belts & replace if required.
5.6.4 Check the condition of the bearings & replace if required.
5.6.5 Lubricate the bearings with AP-3 or its equivalent grease.
5.6.6 Fit the pulleys back to its position.
5.6.7 Fit the ‘V’ belts on the pulleys

5.7 Trial

5.7.1 Switch ON the main supply to the machine.
5.7.2 Check the operation of the machine & set if required.
5.7.3 Check the current drawn by the motors; it should not be more than the rated current.


6.1 SOP: Standard Operating Procedure
6.2 HVAC: Heating Ventilation and Air Conditioning
6.3 UV: Ultra Violet
6.4 QA: Quality Assurance
6.5 AHU: Air Handling Unit
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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