The Process Flow Of Expanded Polystyrene Machine

The Process Flow Of Expanded Polystyrene Machine

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 The process flow of expanded polystyrene machine



Using steam as the medium of heat transfer, the expanded polystyrene machine can be divided into two types, batch pre-expanding and continuous pre-expanding. A vertical cylinder is used for both of types


1.1 continuous expanded polystyrene machine

Normal continuous expanded polystyrene machine, raw material beads are continuously put into the bottom, the expanded particles leave at the top, same as the batch pre-expanding, the particles are constantly stirred, the steam enters at a fixed rate, the pressure at the entrance is maintained at about 0.1 bar-0.3 bar; the expanded particles leave the container through the door on the top of the vessel. Adjust their residence heating time through different feeding speeds; the output of continuous production is very large.

1.2 Batch expanded polystyrene machine

the raw materials put into the vessel after the cold air is removed by the internal steam; at the same time the particles are stirred by the agitator, more steam is added until the required pressure value. As the level of the expanded material rises, the expansion degree of the particle (detected by the level sensor) reaches, the particle will be discharged. Or control the expansion degree of the particle by time (the time density curve is drawn by skilled workers based on experience). The pressure in the vessel exceeds the atmospheric pressure, so the steam temperature exceeds 100 degrees.


Level sensor


Level sensor

1.2.1 The raw material loading

Normally the raw material will be loaded by screw conveyor or vacuum


Screw conveyor



1.2.2 preheating

In order to empty all the cold air inside the vessel, prevent the steam from entering difficult during the main heating process, the temperature of the vessel body varies greatly, the exhaust valve must be opened during preheating


1.2.2 preheating

In order to empty all the cold air inside the vessel, prevent the steam from entering difficult during the main heating process, the temperature of the vessel body varies greatly, the exhaust valve must be opened during preheating

The exhaust valve is imported from Germany

1.2.3 heating

The heating process is divided into penetration heating and insulation.

When the heat source enters through the bottom of the vessel, the temperature in the vessel rises. The heat first passes to the polystyrene in the particle to soften, then to the foaming agent. The gasification and expansion of the foaming agent produces a large number of capillary pores. Finally, the water vapor enters the pores through the polymer and continues to expand until the set expansion rate is reached.

The pressure of foaming agent and steam inside the cavity is balanced with the pressure inside the vessel.

According to the different conditions of equipment and raw materials, different temperatures can be set to control the particle foaming speed. Speed of foaming is especially important for graphite particles and models with high pre-foaming density. Because the addition of graphite inside the polymer makes the particles in the process of expansion, the wall film of the pores becomes very brittle, if the expansion is too fast it will easily burst, resulting in perforation, resulting in an increase in thermal conductivity.

In severe cases, shrinkage and collapse occur in the pre-development process; the setting temperature of the pre-denser particles can control the speed of heat exchange, thus making the density of particles more uniform. Taking the particles with 15kg/m3 density as an example, the white particles expand to a set rate within 40 s, but the graphite particles expand for a relatively long time between 80 and 100s.

There are 2 ways to control the pre production density of inflation rate:

A, by fixing the weight and discharging time.

B by fixing the weight of the feed, the material level reaches the preset height.

It is necessary to ensure that the bottom temperature and the upper temperature are consistent and constant during penetration heating.

1.2.4 decompression stability

Decompression stabilizes the exhaust opening, the bottom heat rises, so that the top temperature rises; but the pressure decreases the overall temperature drops, the particles harden, the water vapor and foaming agent inside the pores begin to condensate, the holes generate a vacuum state, the internal and external pressure to establish a new balance.


1.2.5 discharge fluidization

Fluidized bed drying is a very good treatment because it also restores the pressure in the bubble and makes the particles more suitable for subsequent treatment. Fluidized bed serves as a buffer between the preprocessor and the conveyor in the pre-dispatch and batch processing locations, requiring better product flow.

In most cases, if the air velocity and temperature remain unchanged, air at 20-30 degrees C can meet the pre-drying beads.

The residual moisture content depends on the following factors:

A) the initial moisture content of an initial particle. Usually the expanded particles have a moisture content of about 2-5%, which can reach up to 10% at startup in other special cases.

B) the average residence time in the fluidized bed is reduced by the bulk density of the particles dried by the fluidized bed. The density of 15-26kg/m3 particles decreases by 1 kilograms after drying, but does not affect the pneumatic conveying behind.

1.2.6 density detection

The density of expanded particles should be measured regularly. When setting operation parameters and quality monitoring, it is necessary to measure it manually or automatically.

Density is usually measured by filling expanded particles into a weighed cylindrical box (twice the diameter, 5-10 DM3 in height). Vibrate or tap the box lightly, remove the excess, flatten it with a ruler, and re-measure.

The rigorous steps of filling containers (such as knocking and removing) are particularly cumbersome in manual measurements. But it must be strictly observed, and samples should be extracted from the same place. It should be obtained in the fluidized bed drying area. The volume of containers should be measured at one time.

Automatic density measurement should be set in advance. Weight values are used to control density, such as the speed of feeding in a continuous preset and the weight of feeding in a intermittent preset, and can vary very little from the preset values.


Manual density measurement


Automatic density measurement



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