Publicité
SAFETY PRECAUTIONS
preventing the ingress of flammable atmospheres. Replacement parts shall be in accordance
with the manufacturer's specifications.
NOTE: The use of silicon sealant may inhibit the effectiveness of some types of leak detection
equipment. Intrinsically safe components do not have to be isolated prior to working on them.
8. Repair to intrinsically safe components
Do not apply any permanent inductive or capacitance loads to the circuit without ensuring that
this will not exceed the permissible voltage and current permitted for the equipment in use.
Intrinsically safe components are the only types that can be worked on while live in the
presence of a flammable atmosphere. The test apparatus shall be at the correct rating.
Replace components only with parts specified by the manufacturer. Other parts may result in
the ignition of refrigerant in the atmosphere from a leak.
9. Cabling
Check that cabling will not be subject to wear, corrosion, excessive pressure, vibration, sharp
edges or any other adverse environmental effects. The check shall also take into account the
effects of aging or continual vibration from sources such as compressors or fans.
10. Detection of flammable refrigerants
Under no circumstances shall potential sources of ignition be used in the searching for or
detection of refrigerant leaks. A halide torch (or any other detector using a naked flame) shall
not be used.
11. Leak detection methods
The following leak detection methods are deemed acceptable for systems containing flammable
refrigerants. Electronic leak detectors shall be used to detect flammable refrigerants, but the
sensitivity may not be adequate, or may need re-calibration. (Detection equipment shall be
calibrated in a refrigerant-free area.) Ensure that the detector is not a potential source of ignition
and is suitable for the refrigerant used. Leak detection equipment shall be set at a percentage of
the LFL of the refrigerant and shall be calibrated to the refrigerant employed and the appropriate
percentage of gas (25 % maximum) is confirmed. Leak detection fluids are suitable for use with
most refrigerants but the use of detergents containing chlorine shall be avoided as the chlorine
may react with the refrigerant and corrode the copper pipe-work. If a leak is suspected, all
naked flames shall be removed/ extinguished. If a leakage of refrigerant is found which requires
brazing, all of the refrigerant shall be recovered from the system, or isolated (by means of shut
off valves) in a part of the system remote from the leak. Oxygen free nitrogen (OFN) shall then
be purged through the system both before and during the brazing process.
12. Removal and evacuation
When breaking into the refrigerant circuit to make repairs or for any other purpose conventional
procedures shall be used. However, it is important that best practice is followed since
flammability is a consideration. The following procedure shall be adhered to:
Remove refrigerant;
Purge the circuit with inert gas;
Evacuate;
Purge again with inert gas;
Open the circuit by cutting or brazing.
8
The refrigerant charge shall be recovered into the correct recovery cylinders. The system shall
be flushed with OFN to render the unit safe. This process may need to be repeated several
times. Compressed air or oxygen shall not be used for this task.
Flushing shall be achieved by breaking the vacuum in the system with OFN and continuing to
fill until the working pressure is achieved, then venting to atmosphere, and finally pulling down
to a vacuum. This process shall be repeated until no refrigerant is within the system. When the
final OFN charge is used, the system shall be vented down to atmospheric pressure to enable
work to take place. This operation is absolutely vital if brazing operations on the pipe-work are
to take place.
Ensure that the outlet for the vacuum pump is not close to any ignition sources and there is
ventilation available.
13. Charging procedures
In addition to conventional charging procedures, the following requirements shall be followed.
Ensure that contamination of different refrigerants does not occur when using charging
equipment. Hoses or lines shall be as short as possible to minimise the amount of refrigerant
contained in them.
Cylinders shall be kept upright.
Ensure that the refrigeration system is earthed prior to charging the system with refrigerant.
Label the system when charging is complete (if not already).
Extreme care shall be taken not to overfill the refrigeration system.
Prior to recharging the system it shall be pressure tested with OFN. The system shall be leak
tested on completion of charging but prior to commissioning. A follow up leak test shall be
carried out prior to leaving the site.
14. Decommissioning
Before carrying out this procedure, it is essential that the technician is completely familiar with
the equipment and all its detail. It is recommended good practice that all refrigerants are
recovered safely. Prior to the task being carried out, an oil and refrigerant sample shall be taken
in case analysis is required prior to re-use of reclaimed refrigerant. It is essential that electrical
power is available before the task is commenced.
a) Become familiar with the equipment and its operation.
b) Isolate system electrically.
c) Before attempting the procedure ensure that:
Mechanical handling equipment is available, if required, for handling refrigerant cylinders;
All personal protective equipment is available and being used correctly;
The recovery process is supervised at all times by a competent person;
Recovery equipment and cylinders conform to the appropriate standards.
d) Pump down refrigerant system, if possible.
e) If a vacuum is not possible, make a manifold so that refrigerant can be removed from various
parts of the system.
f) Make sure that cylinder is situated on the scales before recovery takes place.
g) Start the recovery machine and operate in accordance with manufacturer's instructions.
h) Do not overfill cylinders. (No more than 80 % volume liquid charge).
i) Do not exceed the maximum working pressure of the cylinder, even temporarily.
j) When the cylinders have been filled correctly and the process completed, make sure that the
cylinders and
SAFETY PRECAUTIONS
9
Publicité
