This Method Statement is to provide guidance in carrying out the water supply system chlorination in accordance with the approved project quality plan, contract specifications and commissioning plan.
Purpose of this Method Statement is to control the commissioning activities in line with the Project Quality Plan and Project Commissioning Specification requirements to achieve the optimum results.
All precommissioning and commissioning activities of Water Supply System (Chlorination) to be conducted by chemical supplier under direct supervision of commissioning team. Team shall check the Commissioning works prior to submission for consultant/client inspection and approval.
In case of failure in any test, the commissioning team will rectify, and re-offer the test for reinspection and approval.
All Original Test reports witnessed and approved will be retained by the commissioning team. A copy of the final testing & Commissioning Report for Water Supply System (Chlorination) will be forwarded to client for approval.
All commissioning results shall be prepared, obtained and maintained by the commissioning team as given in this procedure.
Instruments & Tools
- Mechanical Plumbing Tool Kit
- Chlorine Testing Kit
All the instruments engaged for testing shall have valid calibration and certificate should be furnished.
Water Chlorination HSE Requirements
Competent Testing and Commissioning team with Specialist Subcontractor Employees are only allowed to mix the Chlorination chemicals to the Water Supply System.
The areas must free from dust and construction debris.
Competent Operatives from the Specialist subcontractor and T&C team must inspect the mixing unit and the connections to avoid the leakage.
Supporting documents for the competency of the specialist contractor employees, third party inspection certificates for the equipments, must be provided to safety Department prior to start the chlorination work.
Arrange sufficient lighting (provide task light) and ventilation (Provide Pedestal Fan) in the work area.
Conduct a special training and explain all the employees regarding the hazards, precautions and emergency procedures (including the precautions mentioned in the MSDS and CoSHH Assessments).
Refer the CoSHH Assessments for the Chlorinated Chemicals for arranging the required personal protective equipments and ensure its correct usage while mixing.
Evacuate all the employees whoever not necessary for the operation from the Chlorine Mixing Area.
Ensure the physical competency of all the operatives prior to start the work and at the end of the shift.
Before start doing the testing evacuate all the Combustible Materials and Unwanted Tools from the Plant Room.
Provide adequate information to others working nearby and display warning signage’s in all the water outlets (Danger Chlorination Going on, No Unauthorized Entry, Do not use and Drink this Water, etc…).
Maintain housekeeping throughout the work activity.
Responsible Site Engineer must be present at all the work area to ensure the work being conducted safely as low as reasonably practicable.
For energizing the Water Pump for the Chlorination; the testing commissioning team must follow the approved Lockout/ Tag out Procedures without fail.
Isolate all the electrical devices which are not necessary through the Lock out Tack out procedures.
Ensure adequate power supply through isolating devices RCD’s, ELCB/GFCI.
Arrange one competent operative as watchman (24 hours) to control the unauthorized usages and monitor the leakages.
Use Rubber Hand Gloves, Respirator Mask and Transparent Safety Goggles for more care.
Display suitable numbers of Emergency Contact Numbers including Chemical safety Team on the remote locations.
Any spillage in the work area shall be informed and cleared immediately.
In case of any major spill; isolate the power supply and stop the spread out if possible and contact the HSE Team/ Chemical Safety Team
immediately.
After the testing the waste water shall drain to a temporary tank and disposed by a licensed third party.
Chlorination Method Pre-Commissioning Phase:
Pre-Commissioning Checks- The main objective here is to prepare and check the installation of piping and domestic water tank prior to Chlorination of the Water Supply System.
The following checks will be made and recorded on the test sheets.
Check that the booster pump is installed and operational.
Check that all filtration, softener, water heaters & calorifiers systems are bypassed prior to chlorine application.
Check that the isolation valve is installed for inlet and outlet.
Check if the strainer is installed.
Verify that the piping system tests are complete.
Verify that the tank installation is approved and the required test is completed.
Commissioning Procedure for Chlorination
Isolate the system to be treated from public use.
Attach suitable hazard warning notice at all main entrances like toilet areas, tank room and the like.
Fill the water tank with fresh water and run the booster pump to distribute the water to the whole system
prior to flushing.
Drain the water tank and the distribution system to empty and physically clean, to remove all deposits of rust, slime, sediments, scale and other fouling, as far as is practicably possible.
Fill the water tanks again with fresh water and then close off the make-up supply line.
Chlorinate the water in the water tank by adding the approved chemical or Tablets, to give a measured free chlorine level of minimum 50 ppm in the water.
This can be measured using testing chlorine kit provided. Yellow color indicates 50 ppm and above, otherwise additional chemical tablet is required.
After an hour, Charge the system with the chlorinated water from the water tanks. Note: All filtration, softener, water heater and calorifier systems should be bypassed.
After Chlorinating the water tank and pipeline, each draw off fitting should be successively opened working progressively away from the water tank & pipeline.
Each tap and draw-off fittings should be closed when the water discharging begins to smell of chlorine.
Note: The water tanks & pipelines must not be allowed to become empty during this operation, if necessary it must be refilled and chlorinated as above.
The water tanks and pipelines should remain charged for 24 hours.
After 24 hours, Open a selection of outlets, including those furthest or highest from the water tank, measure the free chlorine level.
If the concentration of the free residual chlorine is less than 30 ppm (Using Testing Kit, pink color should be produced) the disinfecting must be repeated. Otherwise, drain 20% of the water in the water tank.
After Draining Dose chlorine neutralizing solution @ 1.55 ppm per 1 ppm of free chlorine.
After the addition of neutralizing solution, charge fresh water tank with fresh water equivalent to the 20%
that was previously drained.
Wait for 3-4 hours before charging the system. In charging the system, all outlet/taps to be open to release
the water until the water coming out of the taps are clear and not smelling chlorine.
Sample for microbiological test has to be collected from designated location.
The sample will be tested by approved laboratory.
Final Certification will be provided upon satisfactory completion of the above procedure.
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