The general layout of a unit used for storing, preparing, dispensing and distributing reagents must be designed with the following recommendations in mind.
Storage must be designed to ensure that the products are protected from frost, heat, light and weather conditions. E.g.:
- bleach can breakdown under the effects of heat or sunlight;
- concentrated sodium hydroxide solutions will crystallise at ambient temperature. Tanks used must be installed in heated premises or trace-lagged (sodium hydroxide at 50% by weight will crystallise from 10°C. Refer to the crystallisation curve in figure 20, chemistry and reagents);
- when storing and transporting crystallised ferric chloride (FeCℓ3, 6H2O), temperatures over 37°C must be avoided because, at this temperature, the product will melt before setting as it cools;
- chlorine storage facilities must be protected from the sunlight, especially in hot countries. In the region of 70°C, in fact, as the liquid expands, the free space in the top of the reciever disappears. This could cause the reciever to burst and cause instant vaporisation of the chlorine gas (fatal).
Premises must be heated in winter because a source of external calories is required:
- to maintain the draw-off gas flow;
- to prevent liquefaction from occurring in pipelines as this could damage the chlorometers.
ease of operation
Whenever possible, preference must be given to gravity feed, especially in the case of powder products.
One exception: hazardous liquid reagents (acids-bases) must not, unless special provisions prevail, be stored overhead, especially above personnel access or over areas occupied by equipment.
Similarly, routing any piping conveying a corrosive product above electric equipment (motors and control panels) is not advisable.
When possible, chlorine storage must be located away from or at least separate from other parts of installations.
It is necessary for the locations where lime and activated carbon are handled to be isolated by airtight partitions, doors and windows. These facilities are normally equipped with an air filtration system.
Any automatic flocculant powder preparation must be undertaken in locations that are protected from humidity (solid flocculants are extremely hygroscopic).
Electrical control panels must be installed in locations that are protected against humidity and against dust emitted by powder reagents.