These systems are equipped with a chopper fan which extracts the trim and disintegrates it into small pieces and blows these further to a pulper along a pressurized conveyor duct.  The chopper fan, which is a compromise between a chipper and a fan, has a low efficiency (approximately 30%) and a high noise level. Moreover, the cutting blades require regular inspection and conditioning.Because the paper trim ribbons are chopped up with this trim handling method, depending on the grade of paper, dusting and housekeeping can be a problem.

These systems are equipped with injectors, through which the trim is passed unbroken and blown to a pulper, using a large amount of surplus air. The surplus air typically more than doubles the required air flowrate for trim conveying.  Furthermore, the installation usually includes two blowers arranged in series, which results in even lower efficiency (10-15%) and a higher noise level than the chopper fan system described above.

Another inconvenience which occurs with both the chopper fan and the injector conveying systems described above is caused by the large amount of air blown into the pulper with the trim. As a consequence of this large amount of surplus air, a seperate exhaust system must be installed for the pulper.  Experience has shown that these exhaust systems tend to be very problematic, and they add to the overall trim handling system power consumption.

The following is characteristic of the BERVAC trim handling system.

• The trims are conveyed unbroken under low vacuum from a winder, rewinder, sheeter, rereeler, coater, etc. to the pulper
• The trims are separated from the air stream in a separator of special design, using stock or white water.  The BERVAC system is connected to the pulper with an effluent pipe.  The stock and white water supply is commonly taken from the pulper circulation and supply lines
• The pressure differential required for trim conveyance is produced with a centrifugal fan of high efficiency (in excess of 80%).  As a result, the power consumption of the BERVAC system is only a fraction of that of the conventional trim conveying systems.
• A pulper exhaust system is not required.
• Dimensioning and detailing of a BERVAC system requires a thorough study of the winder, and minor changes are occasionally required at the machine in order to obtain a smooth removal of trims.  These changes often make it possible to increase the maximum trim width up to 250 mm.
• The BERVAC trim handling system is flexible and allows quite long conveying distances.  As a result of this, the nearest pulper does not necessarily have to be used.  It is often possible to reduce the running time of the winder pulper,  for example,  with a timer, or in some cases, the pulper may be shut down altogether.
• Several slitters,  winders,  rewinders, sheeters, coaters, rereelers, etc. can be connected to the same BERVAC system, and their trims may be treated and conveyed simultaneously.  A prerequisite to this, however, is that the system has been dimensioned with consideration to the number of trims, and that the trim qualities allow them all to be conducted to the same pulper.  In a case where the same BERVAC system is to serve several machines, it should be noted that , once dimensioned for all machines, the BERVAC trim conveying system operates with all machines running just as well as with only one machine running. This benefit allows the various machines to be connected to the BERVAC system successively.