Wasting energy through steam loss
May 1st 2007 Tim Gardner, managing director of Gardner Energy Management looks at
reducing energy lost through poor management of steam
In the past, energy management was not
a core function for many processing and
manufacturing companies. However the
continuing and unwavering increase in
energy prices together with ongoing
legislation regarding carbon emissions has
put energy management on the boardroom
agenda. Across manufacturing, including
the food, drink and chemical sectors, the
amount of energy spent is £1.8 billion, of
which 12% (£226 million) is wasted.
Unfortunately, more energy is lost in
industry through steam wastage than
through any other medium. Research
studies by industry experts in early 2000
suggested that losses from steam systems
make up approximately 35% of all identified
potential energy savings. The three
important functions of a steam trap are:
To discharge condensate as soon as it
is formed
Not to allow steam to escape
To be capable of discharging air and
other condensable gases
However around 10% of mechanical
steam traps will fail each year. Traps that fail
'open' result in a loss of steam and its
energy. Where condensate is not returned,
the water is lost as well. The result is
significant economic loss, directly via
increased boiler plant costs, and potentially
indirectly via decreased steam heat capacity.
Steam leakage is a visible indicator of waste
and accounts for up to 11% of steam
consumption in a small or medium scale
industry rising up to an astonishing 55% in
high usage processing industries.
Steam traps can have different sized
orifices to suit different conditions. If a trap
leaks steam, the amount wasted will depend
on the size of the trap and the steam
pressure. The cost of waste will also depend
on the number of traps and the operating
time. For example a process plant with 200
traps based on an average trap size of DN20
and a stream pressure of 14-bar g with 10%
failing annually will have steam wastage of
8900 tonnes. If the overall cost of steam for
this plant were £10 per tonne, the direct cost
of ignoring these leaking steam traps would
be £178,000 each year, which is equivalent
to well over a million litres of fuel oil. The
cost to the environment would be 3000
tonnes of CO2 dumped into the atmosphere.
To be efficient and economical, a steam
trap has to:
Minimise the loss of steam
Provide long lasting and dependable
service by minimising trap testing,
repair, cleaning, downtime and other
associated losses
Be corrosion resistance to prevent the
damaging effects of acidic or oxygenladen
condensate
Ventilate air for efficient heat transfer
and to prevent system binding
Remove CO2 to prevent the formation of
carbonic acid. This means that the
steam trap must function at or near
steam temperature since CO2 dissolves
in condensate that has cooled below
steam temperature
Operate against the actual backpressure
build-up in the return lines
Be free of the dirt collected by the
condensate as it travels through the
distribution piping and on to the boiler.
Even particles passing through strainer
screens are erosive and, therefore, the
steam trap must be able to function in
the presence of dirt
Selecting the correct type of steam trap is
an important element of any steam system.
While Thermostatic, Thermodynamic and
Mechanical are extensively used, the Fixed
Orifice Condense Discharge Trap is now
becoming increasingly used. Instead of
using a valve mechanism to close off steam
for maximum energy and water
conservation, the venturi orifice design
effectively drains condensate from the steam
system. As these steam traps have no
moving parts to wedge open or fail, they
provide the ultimate in reliability necessitating
only minimal maintenance and requiring no
spares, testing or monitoring equipment.
They are available in a range of options for
specific applications, manufactured from
corrosion resistant stainless steel and are
performance guaranteed for 10 years,
obviating the need for repair or replacement.
The hard reality of a plant maintaining its
boiler and forgetting about the rest of the
steam system can be a horribly wasteful
proposition. Losses can include not only
wasted energy but also replacement of
damaged equipment and misuse of manhours.
Fortunately, installing low
maintenance orifice venturi steam traps
can avert much of these potential losses. More articles from Gardner Energy Management Ltd: | 
