Method Statement Title: Flushing and Chemical Cleaning of Chilled Water Piping System – Supplementary
SEQUENCE OF CHW SYSTEM FLUSHING
- Isolate the floor branch pipes from the risers by valves at Location `A’ as shown in the attached sketch.
- Open all FCU valves (at location `B’) and fill clean potable water.
- Pressure test the floor piping including FCUs and valve package connections. Offer for witnessing.
- Release the pressure but retain water in the floor branch circuit till final flushing time.
- Repeat the above procedure for all the floor’s branches.
- Ensure that all floor branch valves are closed (at location `A’)
- Pressure test the entire header pipes circuit including the risers (through C1, C2, C3, C4, C5, C6 and C7). Offer for witnessing.
- Drain the system (excluding floor branches – valves closed at `A’) through drain valves provided at the bottom of risers and in the HEX room (at the bottom of trench pipes below entry point to HEX room).
- Refill the entire system with clean water.
- Ensure that the system is free of air by properly venting the system.
- Ensure that the heat exchanger valves at `C’ are closed and open the flushing bypass valve (at location `D’) provided across the heat exchangers.
- Isolate FAHU coil by keeping the 3-way valve (at location `E’) in the bypass mode.
- Open the flushing bypass valve provided at the end of risers (at location `F’).
- Start the secondary chilled water pumps (SP) and run for 2 hours.
- Drain the system as given in Procedure 8.
- Clean all strainers.
- Refill the entire system with clean water.
- Start and run the pumps.
- Open the floor branch valves at location `A’ for 5 floors and circulate water for 2 hours and close the valves.
- Repeat procedure `19’ for all other floors (i.e., with 5 floors branch valves open at a time).
- Open all floor branch valves.
- Drain the entire system.
- Clean all strainers.
- Refill the entire system.
- Start and run the pumps.
- Bleed of the system at bottom drain points and add make up water continuously until the water appears clean.
- Clean all strainers.
- Close all drain valves and ensure that the system is full of water and free of air by venting at the highest points.
- Add chemicals in required quantities as per specialist supplier’s instructions.
- Samples of water shall be collected from various part of the system to ensure the chemical solution has reached all parts of the system.
- Run the pump and circulate the water (with chemicals) for a period of 24 hours minimum and 72 hours maximum as per specialist suppliers’ recommendations.
- Stop the pumps after completing procedure number 32.
- Drain off the system from the drain valves (at locations described in procedure number 8) into the disposal tankers to be arranged by NMX.
- Refill the system with clean water and drain again at all drain points to remove the traces of chemicals in the system.
- Refill the system again with clean water and run the pumps.
- Bleed off the system at the bottom drain points and add makeup water continuously till water runs clear and chemical analysis report indicates that parameters are within the limits to add the final treatment chemicals.
- Raise WIR before adding the final chemicals for witnessing.
- Safety
- The area shall cordoned off and warning signs shall be placed as required during the process of flushing and cleaning.
- Only competent personnel shall be engaged for flushing and cleaning.
- All PPE shall be used as required by the technicians involved in the activity.
- Safety officer shall check and ensure all safety precautions are followed as per the project safety plan.
- Chemicals shall be stored in a proper place due to health hazard.
- References
- Specification section 15200
- Enclosed sketches showing the typical location of equipments, valves, etc, for low rise and high rise circuits.
