The purpose of this method statement is to define the steps to implement the correct practices for the installation of chemical dosing system (pot) for chilled water piping.
By following this procedure contractor shall ensure that the performance of the chemical dozing system and equipment complies with the project requirements and serves the intended function to satisfactory level.
Best performance of the dosing system shall ultimately ensure that the chilled water quality is maintained as required for long term use and stability of the chilled water dosing system and the main piping system, hence satisfactory performance of the HVAC system.
Ensure progressing of work is coordinated with the Main contractor, MEP Coordinator and Safety Officer, for a safe and proper execution of the works.
Also ensure full coordination with the safety officer to maintain safe working and proper housekeeping of the site, following the approved safety measures and further ensure that all execution working team are aware of the same to prevent accident and losses.
Tools / Instruments
- Dosing Pot
- Valves and associated accessories
- Chilled water piping system
Installation Procedure
Before performing the testing & commissioning of the chilled water dosing make sure that installation is done as below:
- Valves and other accessories are installed as per the approved shop drawings and manufacturer instructions.
- Ensure approved MEP coordination drawings are available for the confirmation of the final location of the dosing system.
- Make sure that the location of the system is as per the shop drawings, if there is any change should be approved by consultant.
- Remove the packing and ensure that the system is free from transportation damages.
- For wall mounted control panel the exact location of panel and fixing holes to be marked based on approved shop drawing.
- Install the control panel as per drawings / details.
- Also install the dosing tank on the plinth and fix properly.
- Provide drain point from the dosing tank to the nearest common drain.
- Mount the dosing pump on top of the dosing tank / wall.
- Ensure that the suction valve of the dosing pump and the flexible tubing are in straight position.
Electrical Connections
- Check that the power supply is available.
- All the wirings for the panel is completed and tested
- All the wirings for the field instruments are completed
- Check for the tightness all wiring connections and are intact.
Dosing System Accessories Installation
Install the low-level switch in the dosing tank as per supplier recommendation.
Install the conductivity probe in a bypass loop across the return and supply header.
Ensure that the probe is in continuous contact with moving water.
Ensure that the probe Tip does not touch any metal parts.
Provide valves across the bypass loop in order to isolate the loop and take the probe for cleaning.
Provide one separate ½” taping in the suction or return header for injection point of scale & corrosion inhibitor dosing system.
Provide one separate ½” taping in the suction or return header for injection point of biocide dosing system.
Provide valves in these tapings for removing the injection valves for maintenance.
Install the impulse water on the makeup water line.
Tighten all connections as required
Check that adequate space is available for maintenance.
Inspection request shall be raised for the consultant/client inspection and approval.
Install the agitator on dosing tanks.
Identification Tags and permanent markers shall be provided for all the modules and devices as per the Requirement and approval of the project and authorities
Testing Procedure for Chemical Dozing System
Fill the dosing tank up to 50 litter mark.
Remove the discharge pipe of the dosing pump.
Give power to the system and prime the pump (In hand mode) and then reconnect the discharge pipe.
Supply power to the conductivity controller.
Set conductivity of the controller.
Switch the dosing pump to auto mode.
The dosing pump will start injecting chemicals when the conductivity is less than the set point.
Fill the dosing tank with recommended chemicals as necessary.
Tag all equipment, stations and other components at which tests have been satisfactorily completed.
Safety Requirements
Before commencing any works, all employees will attend a site safety induction training to ensure all safety measures are understood and implemented and to cover specific procedures in case of emergency. If necessary, practical training exercises will be conducted on escape routes, signage, evacuation and rescue.
All safety precautions shall be followed as per the established Project Safety Plan.
Only experienced and skilled technicians shall be engaged for carrying out installation Start-up and Commissioning of chemical dosing system (pot) of chilled water piping installed.
Safety guards shall be in place and secured prior to start-up of any motor or pump etc.
Cable test reports shall be verified prior to energization of the system.
Appropriate warning signs and tapes shall be placed during start-up and commissioning as required.
All PPE shall be worn as appropriate according to the nature of the job.
Work area shall be maintained neat and clean.
Attachments:
Installation Checklist
Commissioning check lists
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