English (GB)
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2.4 Process description
For locating the components, see figures
.
2.4.1 Selcoperm
Sodium hypochlorite solution (the product) is prepared in a simple
batch process, initiated by the level within the product tank (M).
The water for the electrochlorinator should be supplied to mains
water supply (C) via a double non-return valve. Water enters the
system via an isolating valve (16a). The water passes through a
pressure reducing valve (10) to ensure a regulated pressure
throughout the system. All water then passes through a water
softener (4). Softened water passes into the brine tank (A), via
isolating valve (16b) to produce a brine solution. This is regulated
by the floater valve (21) within the brine tank (A). Saturated brine
is then available for regeneration of the softener (4) via isolating
valve (16c), and for the brine pump (3) via isolating valve (16d).
The process is initiated by the level sensor (25) in the product
tank (M). When the product level falls below the start-fill level
(25a), the water solenoid valve (5) opens, and allows softened
water to flow through the flowmeter (6). When this water flow
raises the magnetic float within the flowmeter (6) the flowmeter
switch (20) is triggered and starts the brine pump (3). The pump
doses saturated brine into this water flow via the injection valve
(15). The resulting diluted brine solution of 20-30 g/l NaCl passes
through the electrolyser cell (1). If no fail safe is triggered, a
voltage is applied across the electrolyser cell (1). When the
electrolyser cell (1) is completely filled with liquid, and the
degassing column level sensor (9) is activated by the liquid, a
current flows. The resulting product (sodium hypochlorite
solution) leaves the electrolyser cell (1) and enters the
transparent degassing column (2). Then it flows into the product
tank (M).
When the product reaches the stop-fill level (25b) in the product
tank (M), the process is stopped. The process is restarted when
the product level in the tank (M) falls below the start-fill level.
The process can also be started manually via control (28).
While the unit is generating the product, hydrogen gas produced
in the process is removed in the degassing column (2) and is
passed through a dual-contained seamless pipe (11) to a safe
ventilation discharge point. An air dilution fan (19) is fitted to
dilute the hydrogen gas to a maximum dilution of 25 % of the LEL
(Lower Explosive Limit). The air is blown continually through the
electrolysis and degassing chamber and through the
dual-contained pipework to prevent localised accumulation of
hydrogen. An air flow sensor (13) is fitted to shut down the
electrochlorinator in case of a blockage or restriction in the
ventilation line (12), or if the sealing cover of the electrolysis and
degassing chamber is removed.
The electrochlorinator is fail safe. In case of faults the display on
the control (28) shows reasons and initiates a potential-free
contact for an output alarm.
2.4.2 Water softener
Hard water contains calcium and magnesium. The water softener
(4) contains resin beads, which hold sodium ions. When hard
water passes through the resin beads inside the water softener,
the beads attract and hold the calcium and magnesium ions in
exchange for sodium. After this ion exchange process, the water
is soft.
Once the resin beads are loaded with calcium and magnesium
ions, they must be regenerated so that they can continue to
soften water. The salt in the brine tank (A) mixes with soft water to
wash the resin beads. Only clean, soft water must be used to
make the brine. The brine loosens the hardness minerals that
have accumulated on the resin beads, then the system
backwashes and flushes the hardness minerals away trough
waste outlet (E).
Note
Leaky taps and pipes should be repaired to ensure
proper performance of the water softener.
