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Hardness and impurities in the mains water
supply will result in lower dishwashing standards and higher
detergent, energy and equipment servicing costs. That's why
Meiko, a world leading specialist in commercial dishwashing
systems, takes a close interest in water treatment technology
and can provide in-depth advice and a complete programme of
water treatment appliances to suit most conditions.
Dealing with hard water
The majority of caterers are in area where
the water supply is classified as moderately or extremely hard.
This happens because the water contains dissolved chalk,
limestone and other minerals. Changes in water industry sourcing
policies have made matters worse in some areas, adding hard
water to supplies which traditionally were soft.
Water hardness is typically expressed in
Britain in either degrees Clarke or parts-per-million (PPM) of
dissolved solids. Water rated above 7 degrees Clarke or 100 PPM
will cause scale formation on all surfaces which come into
contact with it; i.e. pipes, tanks and heater elements. This
scummy furring-up reduces the efficiency of the equipment and
makes it more prone to breakdown. At the same time, scaled up
elements use up more energy; (scale just 1.6mm thick causes a
12% loss in heating efficiency). Chemical costs can also be
higher because a greater concentration of detergent is needed.
Water Softeners
Meiko offers a complete range of water
softeners which work on the ion exchange principle (sometimes
also referred to as cation exchange or base softening). Units
work by passing water through resins in the form of millions of
tiny beads held in a plastic drum. Passage of water through the
resin brings about a chemical change where the calcium and
magnesium ions in the water lose their positive charge and are
exchanged for non-hardening sodium ions.
The resins should never need replacing but
require regular regeneration. This entails flushing a small
amount of brine through the cylinder and is normally carried out
when the dishwasher is not in use. Regeneration refreshes the
resin while the hardness salts which have accumulated in the
resin pass harmlessly to drain rather than clinging to surfaces
inside the machine.
Duplex Water Softeners
Duplex softeners which automatically
regenerate themselves relative to the flow of water are
available for any dishwashing requirement. These comprise two
cylinders one of which regenerates while the other continues in
use, ensuring a continuous supply of softened water irrespective
of water quantities used.
Water Demineralisation
In applications where the quality of the
finished ware is especially critical, such as high quality
glassware or cutlery, water demineralisation units not only
soften hard water but also, thanks to selective dealkalisation
resins remove traces of heavy metals such as lead, copper,
mercury, etc.
Further 'polishing' of the water is aided
by a carbon filter, which removes any traces of organic matter
and chlorine. The resultant water is chemically pure and leaves
no visible residues when it evaporates, which means the
glassware and cutlery can be washed to exceptionally high
standards with no need for hand finishing. Resins are held in
cartridges which need to be changed at predetermined intervals.
Demineralisation equipment made by Meiko is available in the
form of Partital Demin systems, where the carbonate hardness
(lime) is filtered out of the water without leaving any residues
and the quantity of disturbing materials in the water is reduced
by approximately 50%. Where exceptionally high quality water is
essential, a Full Demin system can achieve optimum results.
These would be particularly suited for use in conjunction with
Meiko cabinet glasswashers.
What is Osmosis ?
Osmosis is the natural process by which
plants and trees take up nutrients from the soil around their
root systems. When solutions, of different concentrations, are
separated by a semi-permeable membrane - a membrane which will
only allow the passage of water and not the dissolved species -
water will naturally pass from the dilute solution to the more
concentrated, in order to make the solution strengths equal.
This phenomenon is called osmosis.
Reverse Osmosis
In applications where a high quality
finish is required on glassware and cutlery, without the need to
hand polish, we recommend the installation of an Osmatron
Reverse Osmosis system.
Reverse osmosis works by passing water via
a high pressure pump through a semi-permeable membrane which
allows the passage of water but not the dissolved solids in the
water, which are concentrated and directed to the drain. Up to
97% of minerals in the water are separated off. Treated water is
stored in the unit and automatically delivered to the
glasswashing machine via an electronically controlled stainless
steel pump. To ensure optimum membrane life, water should be
softened e.g. in a central water softening system.
Water Connection Equipment
UK water industry bye-laws stipulate that
contaminated water in the machine (for example, alcohol from
dirty glasses, or detergent) cannot under any circumstances
siphon back into the mains water supply.
This is not a problem on machines which
are solely connected to an external hot water supply but can be
on machines which receive their water from the cold water mains.
The answer preferred by the UK water industry is an air-break in
the water connection, known as a type A air gap. Should water
flow back, it cannot bridge the gap.
The size of the gap, which can be integral
with the machine or in a separate break-tank, depends on the
gauge of the pipe. Units may also house a booster pump if it is
necessary to deal with loss of pressure on the incoming water.
Meiko offers complete solutions for
connecting machines correctly, the type 'A' air gaps
manufactured by Meiko have been tested and are approved by the
WRc (Water Research Centre). The WRc issues approval listings
called IRN, or Installation Requirement Notes, and failure to
comply could leave the caterer open to prosecution. The lowest
IRN numbers (IRN 000 and 001 indicate that a machine can be
connected to any water supply without needing any extra
fitments.
Matching softeners to needs
Integral water softeners can be
incorporated in Meiko frontloading and hood-type dishwashers and
suit operation with an incoming hot water supply up to 55°C.
Salt for regeneration is located in a 0.8kg capacity container
accessed via the floor of the wash tank, regeneration takes
approximately 25 minutes. Following regeneration, the fill and
final rinse valves are opened to enable the base exchanger and
rinse boiler to be flushed out at full pressure, thus removing
any salt deposits and preventing the formation of chloride which
could otherwise corrode the stainless steel.
Stand alone water softeners are compactly
sized for unobtrusive siting near the feed-in point into the
machine. Units contain sufficient resin to enable heavily used
dishwashers to run for many days before needing regeneration,
which is carried out automatically at time intervals pre-set on
a simple time clock. A manual over-ride button permits variation
of the pre-set times, if required.
The choice of softener depends on how much
water is consumed each day. This is determined by multiplying
the machine's rinse consumption per cycle by the number of racks
handled per day, plus the wash tank volume. Meiko offers a
choice of six automatic softeners able to deal with cold water
in volumes from 665 litres up to 4600 litres before needing
regeneration.
There are also three warm water feed
models to deal with circumstances where unsoftened water is used
in pre-heated form up to 65°C. Booster pumps can also be
supplied if the water pressure is too low.
There is also a choice of hot or cold
water softeners with integral electronic controlled pump set
specifically to deal with low water pressure applications.
For further details and pricing on Meiko
water treatment systems see below, or contact our sales team on
01476 591650.
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