18
19
KDH4756
dehumidifier
EN
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 is absolutely 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 in such
a way 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
when in the search 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.
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 or extingui-
shed. 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 accessing the refrigerant circuit to make repairs 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 it 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 in 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 closed 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 minimize the amount of refrigerant contained in them.
