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7. Repairs to Sealed Components
1) During repairs to sealed components, all electrical supplies shall be disconnected from the unit
being worked on prior to the removal of sealed covers and other parts (if any). If it is necessary
to have an electrical supply connected to the unit 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 when 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 the cables, an excessive number of connections, terminals not made to
the original specification, damage to seals, incorrect fitting of glands, etc.
Ensure that the unit is mounted securely.
Ensure that the seals or sealing materials have not been degraded to a point 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 capacitive loads to the circuit without ensuring that this will
not exceed the permissible voltage and current for the unit in use. Intrinsically safe components are
the only types that can be worked on while live and in the presence of a flammable atmosphere. The
test apparatus shall be at the correct rating. Replace the 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 the cabling will not be subject to wear, corrosion, excessive pressure, vibration, sharp
edges, or any other adverse environmental effects. The check shall also consider 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 searching for or detecting
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 pipework.
•
If a leak is suspected, all naked flames shall be removed / extinguished. If a refrigerant leak is
found (which requires brazing), all refrigerants shall be recovered from the system, or isolated (by
means of shut off valves) in a part of the system that is situated remotely from the leak. Oxygen
free nitrogen (OFN) shall then be purged from 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. Considering flammability, follow best practices. Opening of the refrigeration
systems shall not be done by brazing. Adherence to the following procedures is a must:
a) Removing the refrigerant;
b) Purging the circuit with inert gas;
c) Evacuation;
d) Purging again with inert gas;
e) Opening 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 the atmosphere, and finally pulling down to a
vacuum. This process shall be repeated until no refrigerant is inside 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 pipework are to take place.
Ensure that the outlet for the vacuum pump is not near any ignition sources and that ventilation is
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 the charging
equipment. Hoses or lines shall be as short as possible to minimize the amount of refrigerant
contained in them.
• Cylinders shall be kept upright.
• Ensure that the refrigeration system is earthed before charging the system with the refrigerant.
Label the system when the charging is complete (in case it has not been labeled yet).
•
Extreme care shall be taken to avoid overfilling the refrigeration system.
•
Prior to recharging the system, the pressure test with OFN must first be conducted. The
system leak test shall be performed upon completion of charging, but should be done prior to
commissioning. A follow up leak test shall be carried out before leaving the site.
14. Decommissioning
Before carrying out this procedure, it is essential that the technician is completely familiar with the
equipment and all necessary details. It is good practice that all refrigerants be recovered safely. Prior
to carrying out this task, an oil and refrigerant sample shall be taken in case analysis is required before
reusing the reclaimed refrigerant. It is essential that electrical power is available before this task
commences.
a) Become familiar with the equipment and its operation.
b) Isolate the 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 always supervised by a competent person and recovery equipment and
cylinders conform to the required standards.
d) Pump down the refrigerant system, if possible.
e) If a vacuum is not possible, make a manifold so that refrigerants can be removed from various
parts of the system.
f) Make sure that the cylinder is situated on the scales before recovery takes place.
g) Start the recovery machine and operate in accordance with the manufacturer's instructions.
h) Do not overfill the 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 is completed, make sure that the
cylinders and the equipment are removed from the site promptly and all isolation valves on the
equipment are closed off.
Important Safety Instructions
Important Safety Instructions
