Bruker AVANCE, User Manual

Page: 62 / 110

Utility Requirements
62 H157655_1_008
8.3.4.1 Air Compressors
When choosing an air compressor the following points should be considered:
• Ideally the compressor should be installed in a dust free , cool (use air conditioning as
required) and dry place.
• The compressor must be oil-free . This can be achieved by using membrane or Teflon
coated piston and scroll compressors. The compressor should be fitted with a fine dust
inlet filter.
• The compressor must be capable of delivering the required flow rate and pressure suited
to your particular system (see Compressed Gas Requirements). Generally the
compressor should be large enough so it does not run continuously (e.g. > 50% of the
time), which will cause overheating.
• The extra cost of choosing an oversized system may often be justified. The reduction in
duty cycles will lower maintenance costs and extend the life of the system. A suitable
compressor coupled to an adequate buffer will ensure a more
constant flow rate leading
to better performance. When spinning, the system uses a constant flow of air, but surges
will occur during sample lift.
• Take into account the pressure loss along the line between the compressor and the final
gate valve. The pressure drop depends on the pipe diameters. An internal diameter of 8
mm has been found to be suitable. The plastic tubing used to carry the supply from the
final gate valve to the console has an outside diameter of 8 mm and is supplied by Bruker.
• Some types of dryers , e.g., absorption dryers can use up to 25% of the air flow to
regenerate the drying material. If this type of dryer is used then the output capacity of the
compressor must be sufficient to supply this requirement.
• Many compressors are fitted with dryer and a tray to collect excess water . Regular
checking of the dryer and emptying of the water collector will ensure trouble free
operation. This arrangement is quite satisfactory in environments with normal humidity (<
80%). However in areas of higher humidity (> 80%) a cooling coil with an automatic water
drain must be fitted to the compressor outlet. This will ensure that filters do not become
overloaded.
• Although not directly concerned with air quality, compressors are a source of vibrations
which may interfere with NMR performance. You should consider using a compressor
fitted with a vibration damping housing if it is to be situated close to the spectrometer. The
output noise level should be < 75 dBA.