User manual

14
Some trial and error adjustment of the float valve may be required to
balance the makeup water with tower operation. Ideally, the float valve
setting will be such that no water is wasted through the overflow at pump
shutdown. However, the water level after pump start-up must be deep
enough to assure positive pump suction.
5. Open the valve on the tower bleed line and adjust bleed to the recom-
mended rate. See Water Treatment section on page 20.
6. Continue pump operation for about 15 minutes, after which it is recom-
mended that the water system be drained, flushed and refilled.
7. While operating the recirculating water pump(s) and prior to operating
the fluid cooler fan, execute one of the two alternative biocidal treatment
programs described in the following:
• Resume treatment with the biocide which had been used prior to shut-
down. Utilize the services of the water treatment supplier. Maintain the
maximum recommended biocide residual (for the specific biocide) for
a sufficient period of time (residual and time will vary with the biocide)
to bring the system under good biological control or
• Treat the system with sodium hypochlorite to a level of 4 to 5 mg/L
(ppm) free chlorine residual at a pH of 7.0 to 7.6. The chlorine residual
must be held at 4 to 5 mg/L (ppm) for six hours, measurable with
standard commercial water test kits.
If the fluid cooler has been in operation and then shut down for a dura-
tion of time and not drained, perform one of the two previous biocidal
treatment programs directly to the fluid cooler storage vessel (collection
basin, drain down tank, etc.) without circulating stagnant water over the
cooling tower fill or operating the cooling tower fan.
After biocidal pretreatment has been successfully completed, cooling
water may be circulated over the tower fill with the fan off.
When biocidal treatment has been maintained at a satisfactory level for
at least six hours, the fan may be turned on and the system returned to
service. Resume the standard water treatment program, including biocidal
treatment.
Operation