Equipment for the use of Oxygen Free and Dry Nitrogen
(OFDN) in the field of RAC Servicing Practices
Nitrogen is a natural gas and does not contribute to environmental pollution in
general if vented to the atmosphere. Nitrogen is tasteless, odourless and colour-
less and consists of 78.08 % within the air we breath. In addition, Nitrogen is
non-flammable and does not support combustion. For refrigeration technologies
Nitrogen is available in both, liquid and gaseous form. The nitrogen (OFDN) we
commonly use for servicing refrigeration and air–conditioning systems is sup-
plied and transported in high pressure cylinder.
Commonly RAC used OFDN cylinder are specified as follows:
For the use in RAC installation, servicing and maintenance technologies only
use OFDN gas and cylinders in combination with a reliable and appropriate
pressure regulator to safely reduce the pressure of the gas to a controlled level!
The OFDN gas must only be transferred into the refrigerant circuit by the use of
transfer hose designed and certificated for this purpose. For most cases refrig-
erant transfer hoses may have this classification. Check your refrigerant hoses
for reliable use with pressurised OFDN gas.
OFDN gas in refrigeration is used in general for the following activities:
1. Leak test in combination with a weak soapy water solution (bubble test).
2. Pressure test (strength test) of RAC systems.
3. In mixed concentration with Hydrogen (95% Nitrogen and 5% Hydrogen)
as a so-called Forming gas for Leak Test procedures in combination with
Hydrogen Leak Detectors.
4. Refrigerant circuit flushing to remove contaminants and e.g. to free
blocked components and capillaries from obstructions.
5. Purging of air from pipe work before heating and during brazing (to pre-
vent formation of copper oxides on the inner surface of pipes).
6. Purging refrigerants from pipe work and components during brazing to
avoid production of extremely toxic, acidic and harmful products.
7. To be used as “protective gas” and charged in a system or components
for assembling to avoid introduction of air and humidity.
8. To clean surfaces of heat exchangers (e.g. condenser) from dust and dirt.
In most of the above-mentioned activities OFDN can deploy in addition its fa-
vourable capability to absorb a large part of remaining water content within a
refrigerant circuit during system commissioning procedures.
Note:
Pressure regulators are designed to control the pressure and they are supplied
with gauges to indicate pressure. Regulators do not measure or control flow of
the OFDN media unless the arrangement is equipped with devices (metering
valve or flow meter) specially designed for those purpose.
Cylinder
Content (Litre)
Filling Pressure
(bar)
Gas Content
(m³)
Cylinder gross
weight (ca. kg)
5 200 1 9.8
10 200 1,911 15.7
20 200 3,822 37.0
50 200 9,556 77.7
Purity 4.0 OFDN gas is of 99.99 % and a water content of maximum of 30 ppm.
The nitrogen
vented from a cyl-
inder will reduce
the oxygen con-
tent in the
surrounding area
and can cause
suffocation!
Do not use
oxygen or
compressed air to
pressurize RAC
systems because
when mixed with
oil (e.g. compres-
sor lubricant) for
most refrigerants
these gases can
cause
explosions!
Only use OFDN
gas and pressure
cylinder in combi-
nation with a reli-
able and appro-
priate pressure
regulator.
If possible use
an intermediate
pressure gauge,
equipped with
control valve,
within the Nitro-
gen transfer
hose for system
monitoring
(see next page)
To Next Page
Loading...
