SMC Pneumatics and filtration specialist, domnick hunter have joined
forces to develop hospital water filtration and control systems. The
partnership has already seen the completion of two major installations at
new Scottish hospitals and is poised to take advantage of a developing
sector within the health and safety marketplace
A recent study of domestic water systems in Scottish hospitals revealed
significant deposits of sediments and debris in pipe work, which could
provide nutrient sources and potential breeding grounds for bacteria.
Current NHS for Scotland guidelines now recommend that water supplies
entering hospitals be filtered down from 15 microns at the first stage to
0.5 micron in the final filter phase - recommendations that are now being
implemented in new hospital construction.
SMC Pneumatics and filtration specialist, domnick hunter have jointly
developed automatic water filtration and control systems for two new
hospitals in Scotland - the Law Hospital in Wishaw and the New Royal
Infirmary of Edinburgh. domnick hunter developed the systems in
collaboration with SMC Pneumatics' Gateshead regional centre team,
supported by systems engineering teams at the company's Milton Keynes UK
headquarters.
At Wishaw, a three-stage water filtration system supplies clean water at
the rate of 12.5 litre/s to a high capacity storage tank, holding 48
hours worth of the hospital's total water requirement. All valves and a
back-flush pump are controlled by a system developed by SMC. At
Edinburgh, the partners worked on an almost identical scheme but of
larger capacity. This comprises a duplex, three-stage filtration and
control system to cope with the higher water consumption at the hospital.
With Edinburgh's duplex system, the duty/stand-by line is swapped every
cycle to ensure that no individual line is taking an unfair load and to
eliminate the possibility of any problems associated with water
stagnation. After each duty cycle, the filter line is back flushed with
some of the filtered water to extend the service life of the filter
cartridges. The differential pressure across each filter is continually
monitored and, should this reach a pre-determined level, an additional
back flush cycle is initiated. If the additional back flush fails, an
alarm is flagged, indicating the need for an element change. Different
alarm levels can be set for varying pressure readings to ensure maximum
flexibility of operation.
In all, the control system receives inputs from 13 sensors and provides
outputs for 28 valves and one motor. Logic functions are performed by a
Mitsubishi FX2n series PLC, fitted with additional analogue cards to
accept signals from the pressure, temperature and flow sensors. All
operator input is via a Mitsubishi HMI, with password protection
providing several levels of security access.