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The Challenge - Gland Water Reduction on Rotating Equipment (by Kevin Cahalane)
Aughinish Alumina Ltd uses centrifugal pumps as the main process pump
on site. The vast majority of these pumps use the principle of the packed
gland to seal the pump shaft. This system has worked well over the years
but increases in production have resulted in more pumps being installed
and upgrading of some of the original pumps. As a result gland water used
to seal the glands had increased to approximately 110m3/h. Gland water
contributes directly to dilution in the plant.
Evaporation limits forced the plant to look at water reduction and a
team was formed to try and improve gland water control. If gland water usage
could not be better controlled or reduced then an evaporator of the order
of 100 m3/hr would have to be installed for any future plant expansion.
This has substantial capital costs of around €13M.
A program was developed and implemented to reduce/control gland water
usage. Cross-functional teams involving process and mechanical personnel
were formed in each area of the plant. The gland water flow and pressure
requirements for each pump on site were re-evaluated. Drawings and piping & instrumentation
diagrams were updated and the information was then converted into process
book displays. Thus real time information on gland water flows is always
available plant wide on approximately 200 plus PCs. Training was provided
to fitters and process operators on how to use the process book displays
and identify potential problems. In addition, to raise the awareness of
controlling gland water, weekly reports are issued in the plant information
notes, monthly review meetings are held and regular audits are carried out
in each area. In conjunction with the purchasing department various manufacturers
and suppliers of mechanical seals carried out evaluation programs to identify
pumps suitable for mechanical seals.
AESSEAL plc then took up the challenge to work with Aughinish Alumina
to reduce water consumption by employing mechanical seals and innovative
water management systems.
Considerable improvements have been achieved since the reduction program
was implemented.
Over the last twelve months gland water usage has been reduced by 40
m3/h (10,566.88 gallons per hour) and is currently at 70 m3/h (18,492.04
gallons per hour).
Every 1 m3/h (264.17 gallons per hour) of gland water used in the plant
costs €23.5k ($28.2k US) per year in direct costs to the company.
Approximately €1m ($1.2m US) per year will be saved by maintaining
current flows.
Less pump failures have also occurred together with reduce downtime.
An evaporator is not now required.
To achieve the results obtained, required team work across the different
disciplines and at all levels and is the key to the success of the program.
A further reduction in gland water usage of 25 – 30 m3/h (6,604 – 7925
gallons per hour) is expected/ achievable.
In this single application:
WATER SAVINGS
350,400,000 litres per year /
92,565,869 galls (US) per year
WATER COST SAVINGS
£666,000 per year / €1,000,000 per year /
$1,200,000 per year
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