Candidate Support Pack - Scottish Qualifications Authority

Due to the problems of manual handling as well as adequately packing and balancing a
hydro-extractor, this method of moisture removal is seldom used, except on dedicated
polyester cotton garment lines.
The membrane press (pictured above) is essentially a hydraulic ram with a heavy duty
pliable membrane that envelopes the work to be pressed, to squeeze as much moisture
as reasonably possible from the wet work.
There are two basic types of membrane press:
(a) Single stage unit — which pre-forms the load of work before the press is
automatically activated to squeeze the excess moisture from the formed ‘cake’.
(b) Double stage press — in which the load of work is formed into the cake before
then moving on the conveyor under the membrane press.
The pressure of the membrane press and the time that the cake is being squeezed to
remove the excess moisture will dictate the moisture retention left in the pressed cake of
fabric as well as the productivity from the CTW and from the tumblers.
The target moisture retention, (the amount of moisture left in the pressed articles) is
between 48–55% for cotton. This means that if you have 100 kg dry weight of 100%
cotton work, then when it is ejected from the press it should weigh between 148 and
155 kg. Materials containing mostly man-made fibres, such as polyester, will have a
lower moisture retention as fibres like polyester and nylon do not absorb moisture like
cotton.
Faults on the membrane press are the most common cause for production losses from
the CTW. It is therefore a very important area under your control, and one that must be
monitored and checked regularly.
GC8N 22 — Laundry Operations Level 2 5.67