Purpose of this procedure is to define the step by step method to implement the correct practices for the pre-commissioning & commissioning of chilled water pressurization unit through the guidelines contained herein so as to ensure that the job execution complies with the project requirements and serves the intended function to the satisfactory level of the client/consultant.
The scope of this method statement is testing and commissioning of chilled water pressurization unit installed within the project in accordance with the part of commissioning checks at site.
HVAC contractor shall make sure that all the testing and commissioning activities are conducted as per the contract specifications, approved shop drawings, approved material submittals and manufacturer’s installation and operation manuals.
Below is list of necessary tools and materials for the subject job:
- Chilled water circuit piping in line with the pressurization unit
- Electrical Starter and Cables
- Hand Tools
- Clamp Meter
Quality Control
In general, it shall be ensured by Site Engineer that product manufacturer’s recommendations are followed and shall be monitored by QA/QC Engineer.
Project Engineer shall further oversee the Pre-commissioning and commissioning activity as per the approved method statement for start-up and commissioning of chilled water pressurization unit.
Pressurization unit shall be tested under direct supervision of manufacturer / local dealer’s representatives while respective engineer shall monitor the work progress and final inspection by consultant / Engineer.
Precommissioning & Commissioning Procedures
Mechanical Checks
External pipe work connected to the unit should be supported so as not to stress the pipe work connections.
Water and other connections are intact, and that water is available.
Check operation of water tank float valve, ensuring valve will open, and close drip-tight.
Check inside break tank for any debris or sediment and if necessary drain the tank and clean it.
Generally check over and clean the exterior of the unit, at the same time checking for leaks.
Check that the pressure gauges / switches are installed and are operating properly.
Electrical Checks
Ensure the connected cables have been tested and verify the test reports.
Make sure that all cable terminations are complete and tight as required.
Check the cabling / wiring including grounding is complete and dressing is neat and clean.
Ensure all cable identification and labeling is complete.
Set the overload relay to correct setting as per the Pump motor current on the name plate.
Chilled Water Pressurization Unit Startup and Testing
Before commencing the commissioning procedures detailed below, ensure that the system piping is full with water, also ensure that the unit water tank is full.
Prime the pump by removing the plug at the top of the pump body, and allowing water to flood through, when all air has been expelled, replace plug.
Check that the pre-charge pressures in both the unit pressure vessel and the system expansion vessel (s) are correct.
Close the isolating valve between the unit and system, and switch on the power supply to pressurization unit.
The pump should run up to cut-out pressure, and stop.
Open the system isolating valve, and observe the pressure gauge on the unit.
On falling pressure, the duty pump will start at its cut in pressure.
The duty pump forced to fail to start the pressure will continue to fall until the standby pump starts.
Make sure only one pump ever operates at one time.
Open the valves to the system and switch on.
The unit will run, if required, to bring the system up to the fill pressure.
This ensures that the correct fill pressure has been achieved all the time.
Note the pressure at which the pump starts, and adjust this pressure if required to suit the system fill pressure as required in compliance with project specifications and approved material submittals.
Close the system isolating valve.
Lower the pressure within the unit by draining away the water and note the pressure at which the system low pressure cutout switch operates.
Run the pump, thereby raising the pressure and note the pressure at which the system high pressure switch operates.
Sequence of Operation of Chilled Water Pressurization Unit:
H/O/A switch on off position, the relevant pump stops.
H/O/A switch on hand position, the relevant pump starts provided there is enough water in the feed tank.
H/O/A switches of all the pumps on Auto position, the pumps works automatically based on the pressure demand.
On System pressure demand (Press. SW makes), the pumps starts.
At system pressure satisfaction (Press. SW breaks), the pump stops.
Duty Selector switch in position 1. Pump – 1 will work and the second is standby.
Duty Selector switch in position 2. Pump – 1 will work and the first is standby.
If one pump trips on fault, the second pump will start automatically to meet the same demand.
Health and Safety Requirements
All safety precautions shall be followed as per the established Project Health and Safety Plan.
Only experienced and skilled technicians shall be engaged for carrying out Start-up and Commissioning of Pressurization Unit.
Safety guards shall be in place and secured prior to startup of any equipment’s.
Cable test reports shall be verified prior to energizing the pressurization unit.
Appropriate warning signs and tapes shall be placed during start-up and commissioning as required to isolate the area.
All PPE shall be worn as appropriate according to the nature of the job.
Work area shall be maintained neat and clean.
Attachments
Precommissioning & commissioning check list
Inspection Request (IR) duly signed by the Consultant
Specialist Suppliers commissioning report / document
Health and Safety Risk Assessment
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