Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
008831 en 2020.10
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Maintenance instructions
11.5 Visual inspection
Oil pressure
Check that the oil pressure complies with the recommended cut-out pressure.
Oil level
Check the oil level in the compressor. It is of vital importance for the service life of the compressor
that an optimal lubrication is maintained. The oil must always, as a minimum, be visible in the oil
level glass. If the oil level is below the lowest part of the lower oil level glass, oil must be re-
charged. See also subsection 11.13 Oil charge for correct charge.
Recharging of oil (“topping up”) can be carried out during operation either by means of a hand-
operated oil pump or as described in subsection 11.12 Charging compressor with lubricating oil.
Use the recommended oil only.
Remember to write down drained or recharged amount of oil.
11.6 Measures to be taken
The following describes the measures which must be taken, including information about materi-
als, preparation and implementation.
Noise and vibration
No special requirements are imposed regarding equipment and materials. Inspect the unit, and
check that there is no abnormal noise and vibration. Listen for any knocking or other abnormal
noise caused by poorly clamped pipes or faulty valves.
Evaporating pressure and condensing pressure
No special requirements are imposed regarding equipment and materials. Check on the opera-
tor's panel or manometers that the pressures comply with the specifications issued for the com-
pressor unit in question and that they are within the permissible operating ranges.
Evaporating pressure
The terms “evaporating pressure” and “suction pressure” refer to the pressure on the suction side
of the compressor.
Usually the pressure is the same at the evaporator outlet as at the compressor inlet. The only dif-
ference is the pressure drop in the line. Because of this pressure drop, the pressure at the evapo-
rator outlet is a little higher than on the compressor. The non-return valve in the suction line will
also contribute to the pressure drop.
Normal evaporating pressure
According to fundamental refrigeration engineering principles, the refrigerant absorbs heat from
the medium that is being cooled.
In order for heat to be transferred to the refrigerant, it must boil at a lower temperature than the
temperature of the medium being cooled in the evaporator. A basic rule is that the evaporating
temperature is lower than the temperature of the medium that is being cooled in the evaporator.
This rule sets a maximum value for the suction pressure.
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