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Incubating at Increased Egg Density

04 April 2014

Demand for increased incubator capacity and reduced capital and maintenance costs have required some changes in the design of the egg trays, machine construction and temperature control systems in today's large modern incubators, explains Roger Banwell, Petersime's Hatchery Development Manager.

The poultry industry has seen many changes over a relatively short period of time, but none quite as important as the increase of average capacity of a hatchery. Only a few years ago, a hatchery with a setting capacity of one million eggs per week was considered large, whereas today, we see hatcheries with capacities of two, four or even six million eggs per week.

With this growth come new demands, such as reduced capital costs, maintenance and land purchasing costs. A solution is to increase the egg density of the incubators.

Designing a Honeycomb-shaped Setter Tray

To this purpose, Petersime has created a honeycomb-shaped setter tray, which can hold 12 per cent more eggs on the same surface as the traditional matrix tray.


Organisation of eggs in a matrix (left) vs. a honeycomb (right) structure

Many new challenges and issues needed to be resolved before this new tray could be made into a marketable product. The tray had to comply with high standards in terms of:

  • existing and future egg size handling capabilities
  • strength and durability
  • compatibility with Embryo Response Incubation™ technologies
  • adequate airflow around the eggs inside the incubator
  • compatibility with automation systems and
  • ergonomics.

The final High-Density tray launched into the market has a capacity of 84 eggs.


Extensive CFD (Computational Fluid Dynamics) studies conducted at the University of Louvain indicate an adequate air flow between the eggs.

Increasing the egg density inside an incubator cannot be done without adapting some essential specifications of the machine to ensure optimum incubation performance can be maintained. To this purpose, a new, high capacity incubator was developed: the BioStreamer™ HD or High Density.

Machine Reinforcements

It goes without saying that increased egg load requires increased trolley strength, castor load capacity, tray turning strength, etc.

Equally important, however, is to achieve the correct conditioning of the circulating air. The main goal is to ensure optimum transfer of energy (in the form of heat), fluid and gases. This is achieved by passing conditioned air over and around the eggs in order to create an optimal microclimate.

Logically, with an additional 12 per cent of egg load, at least 12 per cent more heating and cooling capacity is needed to obtain adequate air conditioning. Especially during peak heat production (days 16 to 18 of incubation for chicken eggs), the heat load becomes a challenge and heat damage to the embryos should be avoided at all times. Increased heating elements and larger cooling coils resolve the problem of maintaining the required air temperature.


Larger cooling coils

Twelve per cent more eggs also involves a 12 per cent increase in the production of carbon dioxide and humidity (because of the egg weight loss). Increased ventilation dampers enable the CO2NTROL™ and DWLS™ systems to achieve their targets.

Five-bladed Pulsator

This conditioned air, however, needs to be distributed evenly throughout the entire incubator in order to maintain the necessary degree of energy exchange. This presents more of a challenge.

The logical solution would be to increase the air speed, but this would have brought along additional problems. Increasing the air speed through a greater mass requires an increased pressure differential. This unavoidably creates a broader temperature bandwidth: a side-effect that needs to be avoided at all times.

Ultimately, by adding a fifth blade to the central fan, the Petersime R&D Department found a way to increase the rate of air movement while maintaining a uniform temperature bandwidth throughout the incubator cabinet.

The Petersime central fan unit is often referred to as the pulsator, a name derived from the pulsating action of the rotating centrifugal air movement. In simple terms: as each rotating blade moves towards a given point, an onrush of air is driven through that point with a subsequent inrush as the blade passes.

The graph below shows this action. It can clearly be seen how the introduction of a 5th blade increases the number of pulses, while the air speed (the 'amplitude' or height of the waves) remains the same. This means that the extra pulses have no overall effect on the temperature bandwidth.


Four- and five-blade airflow patterns

Extensive trials at the Petersime R&D hatchery and in the field have shown how incubation performance with increased egg density remains consistently high, both in terms of hatchability and chick quality/uniformity.

April 2014



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