Safe Practices - Fisher & Paykel RF175W Service Manual

diphenyl methane di-isocyanate, or M.D.I. for short. In the past, tollene di-isocyanate, or T.D.I. for
short, was used. When the cabinet is "foamed" in the factory, the pre-mix and isocyanate are
conditioned at a prescribed temperature in advance. When the two ingredients are mixed together
they start to expand. Heat is produced by the chemical reaction, which causes the fluorocarbon-II
to boil, giving off a gas and creating a froth. It is this froth that produces the cell structure. The
size of the cells formed is controlled, to a large degree, by the silicone surfactant, and this is critical
in order to provide the required insulation properties.
Precautions necessary when using these Chemicals:
Vapours from the pre-mix and isocyanate can be hazardous to your health, as can be skin contact
from both liquids. When using foam, make sure that adequate protective clothing is worn and
sufficient ventilation is present to remove the vapours that will be given off by the mixture. Should
any of the chemicals come in contact with your skin, rinse off with water. If a gas torch is to be
used whilst repairing a refrigerator or freezer, care must be taken not to set the foam alight, as
cyanide fumes will be given off, as well as phosgene generated from the burnt fluorocarbon
present. Both of these gases can be dangerous if they are allowed to accumulate, and for this
reason sufficient ventilation must be present when doing repair work that is liable to cause the
generation of gases.
13.3.2

Safe Practices

(a) Do not inhale any vapour from the liquids.
(b) Measure chemicals by weight only and NOT by volume. (Not essential for small quantities
used for filling voids after repair).
(c) Avoid contact with skin or clothing.
(d) Use only in accordance with the recommended safety procedures.
(e) Remove, wash and decontaminate clothing before re-use.
(f) You are advised not to smoke near foam operations.
(g) Isocyanate contact with the eyes:
Splashes of isocyanate in the eye are an irritant and may cause severe chemical
conjunctivitis. If any chemical used in the foaming process enters the eyes, they should be
washed out as soon as possible with copious amounts of clean water for at least 15 minutes.
It has been found that this will require the help of another person to hold the victim's eye open.
Foam that is frothing is particularly dangerous if it enters the eyes.
Contact lenses must NOT be worn when working with isocyanates, for the chemicals can get
in behind these lenses and irreparable damage may occur to the eye while the lens is being
removed prior to flushing with water.
DO'S AND DON'TS WHEN USING THESE CHEMICALS
wear sufficient protection - overalls, gloves and goggles - as directed by supervision or
DO
written instructions.
check that first aid facilities are always near you.
DO
avoid personal contact with the chemical.
DO
wash thoroughly immediately on leaving the work area.
DO
seek medical attention at the first sign of breathing or chest troubles.
DO
take care when using a gas torch in the repair of a refrigerator and protect the foam from
DO
the heat.
provide sufficient ventilation so as to avoid breathing any vapours whenever foam
DO
materials are handled, mixed or poured. THIS IS ESSENTIAL. Cyanide fumes will be
given off, together with phosgene from the fluorocarbon present in each foam cell.
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