DISCONTINUOUS PRE-EXPANDERS

It is no longer a novelty but a technologic reality now affirmed, the Conical Pre-expander of Nuova IDROPRESS S.p.A. presented in 1998 and already manufactured in more than 200 models in only 15 years.
The range of Nuova Idropress expanders usable both for moulding and for blocks include two “small” of 0,8 and 1,5 m3 volume available totally cone-shaped (capacity up to 1,5 ton / hour @ 20 g/l) and six “big” truncated cone with volumes usable variable from 2,0 up to 8,0 m3 (and capacity up to 5,8 ton / hour @ 20 g/l).
The great advantage of the conical machine consists in having a bottom diameter of only 800 mm. in the big models and respectively of 500 mm. and 600 mm. in those small, for which the raw material layer concentrated on the bottom results being always significant, and besides, the centrifugal force that acts on the material during the agitator rotation results reduced thanks to the narrow diameter of the chamber. This does not allow the steam, always injected from the bottom of the chamber, to find preferential ways and it is forced to cross the material ensuring the uniformity of the expansion.
Even the discharging operations of the finished product are carried out directly from the bottom instead of the side, reducing in this way the cycle times and eliminating the contamination problems between a cycle and another. Particularly seen the always higher request of use of the machine both with grey material and with the classical white one, a set of accessories has been developed. These considerably reduce risks of contamination in case of colour / product change, such as introduction of air spouts to automatically clean the common parts of the machine or doubling of loading hoppers for raw material and / or second expansion silos, double sensors for an optimum reading of the white and grey materials.

All these advantages combined to the possibility of sending a great quantity of steam in reduced times and at a precise pressure control and temperature of the steam in the chamber during the various processing phases (by means of proportional valves), allow the machine to considerably lower the cycle times and to maintain a high productivity even if it is necessary to produce low densities.

In the first expansion it is possible to reach densities of 11 / 12 g/l while
 
whenever lower densities are required (up to 7 / 8 g/l) it is possible to equip the machine with a pre-loading silo on a scale in order to carry out even cycles of 2nd expansion loading by weight already expanded eps instead of raw material.
Innovative is also the management of the fluid bed, functioning at discontinuous cycle too, and allowing the density control to check the weight of a single cycle and not the mixture of materials deriving from more subsequent cycles. The fluid bed is heated by means of a steam heat exchanger and thus allows avoiding thermal shocks to the beads during the unloading and drying process phase. The pre-expanded material conveying to the storage silos always occurs with sector rotary valve.
The fluid bed can be equipped with a polished aluminium hood for totally closing the process and helping the possible pentane recycle; the hood is complete with extractable filters for facilitating cleaning. The expansion chamber, the fluid bed, the delumper (to be equipped with screens of dimensions variable in function of the machine use if for blocks or shape moulding) and the various accessories are totally made of stainless steel.
 

Another important innovation introduced by Nuova IDROPRESS S.p.A. on its Discontinuous Pre-expanders is the PATENTED system of Expansion Automatic Control realized through a tracking mobile level sensor placed at the external of the chamber.

The monitoring in real time of the material expansion curve allows to adjust “automatically and in direct” the various process control parameters, therefore releasing the machine from the conventional vaporization cycles “at time”. In such way the machine is able to “auto-adjust” itself taking the task to smooth the non homogeneity of the material to expand and ensuring uniformity and repetitiveness of the set density.
Besides, software personalizing is available for the production management and the expanded material flow control towards the silos and from here towards the block mould or the shape moulding machines.

The machines are managed by a PLC with operator interface on industrial PC, of Fanless type and 15” Touch Screen display. The state of all the parts of the machine is visualized on the supervision system, and a graphic is also present that visualizes the temporal course of the expansion curve and of all the pressures in field.

It is possible to memorize all the parameters of process in specific production “recipes”.
 
The range of Nuova IDROPRESS S.p.A.’s Pre-expanders also include horizontal Continuous Pre-expanders adapt only for the 2nd expansion.