41
A Series Inverter Modular Air-cooled Chiller (Heat Pump)
■ Leak detection methods
The following leak detection methods are deemed acceptable for systems containing flammable
refrigerants.
Electronic leak detectors shall be used to detect ammable 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 conrmed.
Leak detection uids 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 ames shall be removed or 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 o 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.
■ 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 ammability 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 ll until
the working pressure is achieved, then venting to atmosphere, and nally pulling down to a vacuum. This
process shall be repeated until no refrigerant is within the system. When the nal 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 close to any ignition sources and there is ventilation
available.
■ Charging procedures
In addition to conventional charging procedures, the following requirements shall be followed.
(1) Ensure that contamination of dierent 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.
(2) Cylinders shall be kept upright.
(3) Ensure that the refrigeration system is earthed prior to charging the system with refrigerant.
(4) Label the system when charging is complete (if not already).
To Next Page
Loading...
