UFC 3-240-13FN
25 May 2005
Table 4-15. Supplemental Chemical Technology
Film Formation
Inhibitor
Dosage
pH
Zinc
10-20 ppm as Zn
6.5-7.5
14-21 days
Polysilicate
40-50 ppm as SiO2
7.5-8.5
14-21 days
Molybdate
40-60 ppm as Mo
7.5-8.5
14-21 days
4-7.4
Layup of Cooling Tower Systems
4-7.4.1
Wet Layup of Cooling Water Systems and Equipment. Systems and
system equipment such as heat exchangers, chiller tube bundles and the like can be
laid up wet, but first they require a physical cleaning to remove all suspended materials.
Apply corrosion inhibitors at increased dosages, usually at a level of about 4 to 5 times
the normal maintenance dosage. Apply an increased dosage (within EPA limits) of a
non-oxidizing biocide that has a long half-life, such as glutaraldehyde or isothiazolone.
4-7.4.2
Dry Layup of Cooling Water Systems and Equipment. Systems and
equipment can be laid up dry, although dry layup is more appropriate for a single piece
of equipment, such as a chiller's condenser tube bundle or other heat exchanger. All
metal surfaces must be completely dry; residual moisture is not acceptable. In humid
climates you should use a desiccant such as a quicklime gel or an equivalent. Place the
desiccant in as many locations as necessary and replace as required.
140
Previous Page
