6
ňWarnings(for using R290 refrigerant only)
exposed while charging, recovering or purging the system; That
there is continuity of earth bonding.
7. Repairs to sealed components
1) During repairs to sealed components, all electrical supplies
shall be disconnected from the equipment being worked upon
prior to any removal of sealed covers, etc. If it isabsolutely
necessary to have an electrical supply to equipment during
servicing, then a permanently operating form of leak detection
shall be located at the most critical point to warn of a potentially
hazardous situation.
2) Particular attention shall be paid to the following to ensure
that by working on electrical components, the casing is not
altered in such a way that the level of protection is affected.
This shall include damage to cables, excessive number of
connections, terminals not made to original specification,
damage to seals, incorrect fitting of glands, etc.
Ensure that apparatus is mounted securely.
Ensure that seals or sealing materials have not degraded such
that they no longer serve the purpose of 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
he 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
ana 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.
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
