Hi,
Currently a biocide injection line is connected to the drains tank to for intermittent injection. Operations requires that the same biocide be delivered to biocide cells for storage elsewhere in the facility. Under the new arrangement, the biocide will be injected into a vertical line coming from the seawater distribution system (this SW line is not used anymore, the butterfly valve is normally closed - not locked closed).
I have two options:
Option 1: Just install isolation valves on the 2 branches as shown in the attached sketch
Option 2: Install an isolation valve and a check valve on the branch connecting to the vertical section of the SW line to avoid back flow in case the SW supply is resumed for any reason in the future.
Your thoughts?
Thanks,
Sherif