Candidate Support Pack - Scottish Qualifications Authority

Air drawn from outside the building will be a lot less contaminated, but will also be a lot
colder and use more energy to heat.
The air supply that seems to make the most economic sense is the recirculation of the
exhaust air from the tumble-dryer, which is filtered into a fresh air supply. This air will be
quite heavily contaminated with water vapour and lint, which will need to be removed
before it can be re-used. However, the energy required to operate a tumbler-dryer by this
method will be reduced by up to 26 per cent.
Tumble-drying can use up to a third of the total steam consumption of a laundry, so heat
recovery systems can save a lot of money. You should also remember that it is far more
cost effective to remove water from fabric by extraction at the washing stage than by
tumble-drying. You should never be tempted to compensate for poor extraction by
extended drying times.
Filters must be cleaned regularly to maintain good airflows through a tumble-dryer. The
operator will usually be responsible for regular cleaning of the air outlet filter screen.
Maintenance or specialist cleaning personnel will be responsible for other filters and
ducting.
Fans are used to draw the heated air through the load in the tumble-dryer, and it is very
important that these fans are operated at the correct speed and rotate in the right direction
to provide the necessary airflow.
Airflows can be reduced if the perforations in the dryer cage become blocked. The most
common cause of blockages is plastic bags melting in the dryer.
The efficiency of the dryer will be reduced if the tumble-dryer is not sealed properly. This
can be caused by badly fitting filters or door seals, or even by damage to the outer casing
of the machine, which allows air to leak in.
Correct loading of the tumble-dryer is critical to airflows and effective evaporation of
moisture. The moisture retention after washing, the fabric type and the size of the items to
be dried should all be taken into account when maximum loading weights are determined
for different classifications.
Cotton items can generally be loaded to the machine’s capacity, but polyester cotton
should be loaded to approximately 65 per cent of the tumbler’s capacity to prevent
pressure creases forming during the drying cycle. Very bulky items like duvets may have
to be dried at only 35 per cent of the maximum capacity.
GC8N 22 — Laundry Operations Level 2 6.9