Surface World October 2019 Surface World October 2019 | Page 60

PRE-TREATMENT, SURFACE PREPARATION, DEGREASING & CLEANING
Deionisation can also be carried out using
an electro-deionisation (EDI) process,
through which electrical current forces the
continuous migration of contaminant ions
out of the feedwater while continuously
regenerating the ion exchange resins. This is
achieved with hydrogen and hydroxyl ions
that are derived from water splitting. A single
EDI unit may operate for a few years before
a replacement is required, but the up-front
costs associated with the purchase and
installation of such a system can be
significant, as are the costs of running it.
EDI cells are prone to problems such as
scaling and CO2 damage. These issues
with the EDI process can lead to periods
of costly downtime.
For many manufacturers, the most
cost-effective means of getting access to
deionised water will be a subscription-based
service. Leading water purification companies
including SUEZ have invested in a central
cylinder processing facility, taking on all the
capital costs associated with the supply and
regeneration of ion-exchange resins, so that
customers can obtain pure water with
minimal outlay.
The way these services work is very simple.
Taking SUEZ’s Cylinder Exchange Service
as an example, a customer can purchase
the cylinder it needs to fulfil its deionised
water needs. When the resin in this cylinder
is exhausted, the customer sends its
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purchase order or pre-paid voucher to SUEZ.
The company then organises the collection of
the exhausted cylinder, regenerates the resin it
contains at its facility in Peterborough, UK, and
then returns it—all within seven working days.
Regenerating the resin in this manner is more
environmentally friendly than replacing the
resin wholesale. As the customer can own the
cylinder, it is a highly traceable and
transparent system.
Operating cylinders in tandem, so one is in
use while the other is being regenerated,
ensures that any production downtime is kept
to a minimum.
Two types are of deionising cylinder are
available: a general deionising cylinder (DC)
containing exchangeable regenerated resin
and a nuclear-grade deionising cylinder
(NC).
The DC cylinder is a single-pass deioniser
filled with mixed-bed ion-exchange resin and
is capable of removing up to 99% of
dissolved mineral impurities from a mains or
process water. This cylinder is ideal for
surface finishing, the de-fluxing and cleaning
of printed circuit boards (PCBs), ultrasonic
cleaning, humidifier supply, laboratory glass
rinsing, laboratory reagent make-up, boiler
feed and printing solutions, or wherever
water of up to 10 MΩ.cm is required.
The NC cylinder is a deioniser filled with
nuclear grade resin and is able to provide
ultra-pure water up to 18.2 MΩ.cm.
It is principally used in semiconductor,
cosmetics and pharmaceutical production.
For maximum performance NC cylinders are
typically pre-fed with water that has already
been pre-purified by reverse osmosis or
passed through a DC deionising cylinder.
When looking for the right service, efficiency
and reliability are obviously important
factors. But additional things to look for
are features within the cylinders themselves.
Cylinders can be supplied with all the fittings
necessary for connection to a mains or
process water supply. They should also be
designed for ease of use. Look for features
such as colour-coded cylinder heads for easy
identification and a quick and easy release
system that simplifies the job of connecting
the cylinders. Transit plugs will ensure that
cylinder ports are kept clean and that here
is no spillage during transport, while an air
bleed valve will purge cylinders prior to use.
Cylinders should also feature high-efficiency
internal pipework for maximum capacity.
Given the importance of deionised water to all
manner of industrial processes, it is vital that
manufacturers choose the right technologies
for its production and trust their supplier.
As we have seen, a subscription-based system
may prove to be the most cost-effective option
to secure this vital resource.
Visit: www.suez.com
The Institute of Materials Finishing, official sponsors
of Surface World Live, are proud supporters of the
British Surface Finishing Industry.
- we have everything covered
OCTOBER 2019
Hall 11, NEC, Birmingham - 18th & 19th March 2020
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