PV-1 and PV-3 preexpanders

Preexpander is designed for preexpansion of EPS beads by heat treatment. Saturated water steam is used as heat conductive medium.

There are two types of preexpanders:

• continuous operation
• batch operation

We manufacture BATCH OPERATION preexpanders (hereinafter referred to as Preex).

We opt to manufacture a Preex of this type as it has a number of advantages over the continuous operation variety.

Disadvantages of continuous operation preexpanders:

1) Bead density is adjustable by the following three methods, usually, in the following order:

• steam supply adjustment
• infeed rate adjustment
• bypass height adjustment, if any

All the above three methods rely on adjustment of the time the beads are stored inside the chamber.

2) Steam pressure can only be reduced (by mixing it with air) but never increased, as the process runs at ambient pressure (continuous operation preexpanders are open and unsealed). This disadvantage leads not only to a risk of a possible process irregularity but also to increased steam flow and higher costs of steam generation.

3) Average time the material is inside the continuous operation preexpander is about 3 minutes, however, minimum target density of expanded beads is directly related to pentane content.

Advantages of batch operation preexpander:

1) The pressure is adjustable, as the result steam temperature can be selected so as to match the required EPS density or pentane content of the raw material. !!! If steam temperature is outside the required range, steam can damage the cells.

The lower is pentane content, the later is the preexpansion and the higher is the temperature required.

2) Batch operation preexpander is a sealed receptacle that supports lower steam flow and higher preexpansion rate as compared to the continuous operation Preex.

Bead density is adjusted as follows during batch operation of the preexpander:

• adjustment of steam treatment time;
• adjustment of the raw material volume for each feed;
• adjustment of the height of the preexpanded bead layer inside the operating chamber;
• steam pressure adjustment;
• steam volume adjustment.

As we can see from the above, batch operation preexpanders are more flexible and can support lower densities even for relatively small beads. Switching between volumes is quick and the loss is very small.

Standard preexpander types

	PV-1 A preexpander with the capacity of 10 cub.m. per hour, suitable for the complete line with the capacity of 70 to 90 cub.m. per 8 hour shift depending on the skills of operators. Raw material is fed manually through a funnel on top of the receptacle. Beads are discharged through a manually or pneumatically operated discharge door (customer selected option).
	PV-1A (automatic) High-capacity preexpander that could be integrated into the 200 cub.m./shift manufacturing line. Remotely controlled, supports full automatic and manual modes. Raw material is fed using an additional loading screw-type hopper. Batching is by weight. Expanded beads are discharged to a dryer and then to silo hoppers. Expanded beads are transported by air transport with a Venturi tube to avoid deformation.
	PV-3   A small-sized cost-effective batch operation preexpander, capacity: 0,75 cub.m./hour. Ideal for processes where expandable polystyrene is not a primary raw material, such as lost foam casting (LFC), EPS concrete manufacture, production of bean bags, stuffed toys with EPS-based filling; production of tourist and sports gear, etc. Manual feed through a funnel, discharge through a door. Custom manual drive option is available upon request.

Preexpander specifications
(for 25 grade EPS)

Watch the preexpander and dryer in action