• 26/11/2014

    Vacuum-Assisted Technology: now also for existing plants!

Afros panel - new retrofitting kit of insulated panels

A new retrofitting kit allows the manufacture of discontinuous insulated panels making use of existing presses and foaming plants.
Energy-efficient elements of the Cold Chain (refrigerated warehouses, reefer containers, cold rooms, commercial and domestic refrigerators, portable coolers etc.) have proven their effectiveness in reducing the use of energy required to keep our food fresh in its path from “field to table”.

Insulated panels —A growing market

Polyurethane-based insulated panels represent the insulation technology in most of the above mentioned applications.  The demand for these products is growing on a worldwide basis, as is their average thickness.

A complex mix of panel models, made with dedicated manufacturing methods, is available to fulfil any kind of requests from the market in terms of dimensions, thickness, application, fire-resistance rating, and choice of facing, colour, and surface aspect.

Continuous foaming production is preferred for large volume, standardised types of panels.

The discontinuous foaming method is preferred for smaller lots, for higher flexibility, for a mixed supply of sizes, shapes, models and colours.

For both technologies a large number of foaming plants in operation today are facing the challenge of this increased demand, both in terms of overall quantity and new dimensions to be manufactured.

The replacement of Ozone-depleting and Green-house affecting old blowing agents with a new generation of foam-expanding chemicals has caused a general increase in the panel thickness, required to meet the severe insulation specifications that are typical of the “cold chain” structure. Larger panels are demanded for a generation of jumbo refrigerated trucks that are allowed to circulate in numerous countries. The same trend is shown for the reefers, insulated 40’ containers used to transport fresh vegetables, meat and fish overseas.

The demand is growing and numerous manufacturers cannot cope with it simply because their existing plants are not able to produce panels with the technical specifications and productivity required by these new end uses. The obvious solution —to buy a new,  higher performance foaming plant —cannot be taken in consideration by many producers that have not yet amortised their more recent investments in foaming machines and polymerisation presses or laminators.

V.A.I. —The vacuum innovation starts

Cannon and Manni pioneered in the late 1990’s the V.A.I. (Vacuum Assisted Injection) process. With this innovative method a controlled level of negative pressure (vacuum) is maintained in the polymerisation cavity of a panel press for the entire time of the injection. High-quality insulated panels for walk-in cold rooms and cold industrial warehouses can be obtained with numerous advantages vs. the conventional injection system:

  • dramatic improvement in productivity, up to 30% less time for demoulding
  • weight reduction, up to 3% less foam
  • beneficial mechanical and aesthetics properties

In order to obtain the said advantages, a manufacturer ought to use Polyurethane formulations specifically developed for this vacuum-assisted foaming method, and properly designed polymerisation presses and metering-mixing equipment.

The above described manufacturing situation —the availability of existing foaming plants, still in perfect running condition —stimulated the search for a new solution, in order to also provide  to these producers all the advantages deriving from the V.A.I. process.

A retrofitting kit was studied, made and patented by Manni, the Mantova-based specialist in presses for Polyurethane panels. The complete set of equipment —needed to modify an existing discontinuous foaming plant and adapt it to the production of insulated panels using the Vacuum Assisted Injection —is now available.

The new Manni 2.0 Retrofitting Kit for existing presses

The system that allows the use of a vacuum process on existing conventional foaming plants, without applying substantial modifications to the press, consists of the following elements:

  • Venturi vacuum pump
  • Proportional valve
  • Air extraction system
  • Control PLC 
  • Pressure transducer 
  • A new version of injection device

Metering & mixing —New convenient alternatives are available

The metering and mixing equipment required for the use of V.A.I. process is generally the same used for classic discontinuous foaming. High pressure dosing machines with a medium-high output capacity and self-cleaning mixing heads are recommended. The injection operation can be manual or assisted by a manipulator.

In the decision making process that leads to an investment in this new V.A.I. Kit, it would be wise to consider the upgrading of the existing mixing hardware towards the next generation of mixing heads.

Cannon recommends for these applications two different models:

  • the JL (JetLess) that can provide a proven reduction in the consumption of PUR foam, with economic savings in chemicals calculated around 4-5% with a well calibrated system
  • the FPL SR, now available with three diameters of the self-cleaning plunger: 18, 24 and 26 mm. The head features a longer injection nose, extended, in average, by 30% versus the prior version

A new chemistry — Fundamental to obtain the best results

The peculiar advantages obtained with the V.A.I. process and described at the beginning of this article can be optimised with the right combination of suitable processing equipment and the right chemicals.

DOW developed a family of new formulations —available under the PASCAL™ PRO brand —specifically conceived for the use of vacuum assisted injections of rigid foams. They are now available for the sandwich panel industry, to be used with Cannon Manni’s new or retrofitted panel plants.

The advantages obtained using the innovative Vacuum-Assisted Injection of Polyurethane foam in sandwich panels are now obtainable by the owners of existing equipment that do not intend to invest substantial amounts of money in a new foaming plant.

The retrofitting kit Manni 2.0 supplied by Cannon Manni can be applied on most of the current polymerisation presses available on the market, and a modification of the foam dispensing and mixing equipment is not compulsory. By using one of the new Cannon mixing heads designed for rigid insulation foams, these advantages can only be augmented.

 

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