There is a
statutory requirement for the periodic testing of lifting equipment. The
School Safety Officer must be informed of all such equipment brought into the
School. No mechanical lifting is to be undertaken by anyone other than those
members of staff specifically qualified to do so, who are responsible for
conducting the operation safely.
Personal
Protective Equipment (PPE). Suitable PPE must be worn at all times where risk assessment dictates.
Goggles must be worn for any operation which is hazardous or potentially
hazardous to the eyes. Goggles are recommended particularly for use when
working with bromine or volatile bromine compounds, strong ammonia, any
irritating dust, acids and alkalis. They should also be used when making
fusions or cutting sodium, breaking up solidified melts, chipping any hard
materials, opening cylinders containing gas under pressure, when using grinding
apparatus, and when carrying out any operation with a danger of liquid
splashing.
Centrifuges. Centrifuges can be very easily
damaged and are a source of danger when improperly used. At 5,000 rpm, the
periphery of a 10 cm radius rotor is travelling at over 110 mph: never try to
stop a centrifuge with the hand. The load on a centrifuge should always be
balanced accurately before switching on to avoid putting undue stress on the
bearings. Centrifuges should be kept scrupulously clean as corrosion can
seriously weaken the rotor. Only centrifuges specifically designed for low
temperature work should be kept in cold rooms.
Vacuum
Systems. Although
much vacuum apparatus is constructed of glass, it is worthwhile remembering
that an increasing range of equipment made of plastic is now available, including
vacuum desiccators. Unsuitable glassware, e.g. conical flasks other than
thick-walled Buchner flasks should never be even partially evacuated. Considerable
damage can be caused by the collapse of large glass vessels. They should be
exhausted behind safety screens. Do not use a large vessel if a small one will
do.
When vacuum
apparatus is assembled. The equipment should always be examined for stresses
and strains, both before and after filling, (a kilogram of reagents, e.g. 75
mls mercury, can introduce severe strains in glass apparatus). Any glass
vessel that is seriously scratched should be discarded. Sudden changes of
temperature should be avoided and the vessel should be placed on a rubber mat,
or even surface, to avoid any irregular pressure on the base.
Metal or
plastic tubing should be used wherever possible, and flexible items, e.g.
bellows couplings, should be included in the apparatus. Where ground glass
unions are used, ball and socket joints are to be preferred to cone and socket
joints.
As far as
possible, vacuum apparatus should be screened. Equipment should be prominently
labelled when left under vacuum. The risk of implosion with wide bore tubing,
bulbs and items up to about 1 litre capacity can be reduced by strapping with
cloth adhesive tape, cellophane tape, or varnished cloth mesh. Larger items
should be encased in a stout gauge wire screen. Where such precautions are
impracticable the entire apparatus should be placed behind Perspex or stout
wire screens. It is a wise precaution to wear safety goggles when operating
glass vacuum apparatus.
It is
important to ensure that rubber bungs are large enough to resist being sucked
into a vacuum vessel. Stopcocks should always be properly lubricated, operated
slowly and never forced.
There is
serious risk of implosion (and consequently a flying glass hazard) with certain
commercially available equipment. Dewars, for example, the large vessels
present as considerable hazard. With these implosion is most likely as a
result of careless handling. Thermal shock is produced while filling the
vessel with liquefied gas, and allowing it to evaporate before filling. All
Dewar vessels should be in a protective case or at least made shatter-proof by
plastic adhesive tape stuck on the outside. Vacuum tubes of all kinds should
be handled with care. Because of their size the hazard is particularly great
with cathode ray tubes, and special care should be taken not to scratch any
part of the bulb, especially the face.
Vacuum
desiccators and bell jars are frequently treated with contempt. These should
always be screened and never moved whilst under vacuum. They should always be
labelled if left evacuated.
Most of the
safety precautions required for vacuum work apply to high pressure apparatus
but the following points also apply.
Pressure
vessels should be examined by a competent person at least once every period of
26 months or at such intervals as the competent person dictates. The safe working
pressure of each vessel should be marked on it and any pressure relieving
safety devices that are fitted should be so designed as to ensure that in the
event of equipment failure leading to a rapid rise in temperature within the
pressure vessel under test, the safe working pressure will not be exceeded. If
it is not possible to achieve this standard of safety protection then the whole
apparatus must be encased within an enclosure of such strength as will be able
to resist the effect of explosion of the pressure vessel.
Safety
valves and other methods of pressure release should be sited so as to minimise
the chance of injury to people or damage to equipment if they should operate.
Great care
should be taken to use only materials and equipment designed to withstand high
pressures, e.g. seamless tubing etc. Regular inspections should be made to
discover blocked filters, leaking valves, weld crack etc. If glass apparatus
is to be pressurised it should be screened and safety goggles worn by the
operator.
At very
high pressures, serious accidents have occurred due to unexpected chemical
reactions taking place and producing much higher pressure than those for which
the apparatus was designed.
Some
commercially available light sources, e.g. the xenon arc lamps used in
spectrofluorometers are filled under very high pressures. Such lamps should
never be handled without safety goggles.
The
principal hazards in workshops include injuries caused by moving parts, failure
of equipment, incorrect or careless use of hand tools, faulty or damaged tools,
etc. Many accidents in this category can be avoided merely by the correct use
of equipment that is well maintained and inspected. In general, the wearing of
rings, necklaces and bracelets is discouraged and for some work, their removal
will be required.
All
machines, whether hand or power operated should be fitted with appropriate
guards or other safety devices. These should always be used. Protective
clothing, appropriate to the work in hand, should always be worn and long hair
should be tied back and protected by suitable head gear.
Only
qualified technicians or staff/students acting under the supervision of
suitably qualified technicians as authorised by the Workshops Supervisor may
use the workshops facilities.
Welding
should always be carried out in well ventilated booths since toxic gases can be
generated at the high temperatures involved. Special care is necessary with
painted or plated metals. Appropriate eye protection should be worn by anyone
working in or visiting a welding booth while work is in progress. Only
technicians trained and qualified in welding procedures and associated safety
precautions are authorized to operate the School’s welding equipment.
