Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
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Requirements for ambient temperatures and humidity
Sabroe compressor units are generally designed for indoor installation within these limits:
Humidity
:
•
10-90% relative humidity (not condensing).
Temperature
:
Minimum 0°C (+32F). Limiting factors:
•
Avoid freezing of water charge systems during standstill
•
For seamless performance, UniSAB III requires an ambient temperature above 0°C
•
Be aware that some electrical panels may require a minimum temperature of +15°C.
M40°C (+104F). Limiting factors:
•
Most motors have limits of m40°C, unless otherwise specified
•
Centa rubber couplings are derated at higher temperatures.
Equipment for operation outside the above-mentioned temperatures is available on request.
Precautions to avoid condensing of refrigerant in undesirable places
Condensing of refrigerant outside the condenser, for example in oil separators and compres-
sors, is associated with a risk of damaging the equipment due to liquid hammering, reduced lu-
brication and other malfunctions. In principle, condensing takes place whenever the
temperature of the equipment gets below the saturated pressure. To mitigate this risk, all Sab-
roe refrigeration equipment is, as standard, equipped with:
•
Heating element(s) in the oil reservoir on all screw compressor units
•
Heating element(s) in the crankcase on all reciprocating compressors.
These heating elements are normally capable of keeping the oil temperature at least 10K
above the ambient temperature. Despite the above precautions, however, undesirable con-
densing is still a risk if the ambient temperature falls significantly (10-15K) below the system
condensing temperature. If this happens, it should be monitored if the oil temperature stays
above the saturated temperature of the refrigerant. If it does not, these additional precautions
must be taken:
•
Check that standstill heating is active
•
Increase timer on
Oil return start-up delay
to ensure boiling off condensate before oil is
returned to the compressor
•
Increase the ambient (machine room) temperature
•
Add insulation and, if required, heat tracing.
In any case, on systems located outdoors, or in unheated buildings where the ambient temper-
ature may drop below 0°C [+32°F], insulation and heat tracing of the compressor lubricating oil
systems, including oil lines, oil filters, oil pumps and oil coolers, is mandatory. Freeze-up pro-
tection must also be provided for all water-cooled equipment.
For
heat pumps
, the risk of undesired condensing is substantially higher. Factory-built equip-
ment has a number of built-in measures to avoid this (see Technical Information TI 2016-04
and TI 2016-05). For site-built systems, it is the obligation of the contractor to install similar
and adequate means to avoid undesired condensing.
Suction check valve power assistance is not necessary on check valves with linear ball
bearings.