Top-loading Impregnation Equipment

Top-loading machines were the first to be used for impregnation, and were originally based on a simple vacuum autoclave system with open tanks for the subsequent processes.

This technology remains widely used today and Ultraseal can supply standard batch processing machines for start-up and lower volume requirements, offering appropriate levels of process control.

However, recognising the limitations to such simple systems, Ultraseal has focused on developing advanced, value-adding options, with modular approach providing the most suitable, cost-effective solution.

Rotational System Technology

The limitations of traditional batch processing systems, in terms of long cycle times and potential for contamination of parts held in static tanks, has lead Ultraseal to develop a rotational processing system which is available as an option on all of its top-loading systems.

In tandem with rotational technology, Ultraseal pioneered the principle of cascade washing, whereby a copious volume of fluid is pumped through a manifold and over the rotating workload. This provides a more aggressive and effective washing action than conventional systems.

Rotational Processing offers the following benefits:

The Process

Part Preparation

Before impregnation, porosity within the component must be completely clean and dry. Whilst this is achievable through a separate pre-process, Ultraseal offers modules for aqueous washing and vacuum drying that can be integrated into the system.

Impregnation

Ultraseal International offers two types of autoclave with top-load equipment:

Vertical Transfer System (VTS): The workload is suspended in a basket during the dry vacuum phase before being lowered and immersed in sealant. The vacuum is then released, forcing the sealant deep into the porosity. VTS-based impregnation machines are simple in design with the advantage of a relatively small footprint.

Sealant Transfer System (STS): The workload is loaded into the autoclave with the sealant in an adjacent tank. After the dry vacuum has been drawn on the autoclave, a valve is opened and the sealant transfers into the autoclave, immersing the components. The vacuum is then released, forcing the sealant into the porosity, after which the sealant returns to its original tank under vacuum.

Note: For critical applications, a pressure autoclave can be supplied, enabling a pressure cycle to be incorporated following the vacuum phase.

Drain

The drain cycle involves removing excess sealant from the component after impregnation. Effective draining is essential to reduce any ‘carry over’ to the cold wash tank and limit the amount of sealant lost as effluent. While a static drain is suitable in some applications, sealant may become trapped in pockets or within the features of more complex components. A rotational drain system physically rotates the components in their basket to maximise sealant removal. The removed sealant is then collected and automatically returned to the autoclave.

Cold Wash

After draining, the components are transferred to the cold wash tank to remove surface sealant. For more complex components, a rotational system is recommended. The wash solution is pumped from the lower tank into the chamber, passing over and through the rotating workload, before returning to the tank. The workload is not immersed, as if the components were to remain in the water during washing, contamination in the wash solution would adhere to the components and cause potential cleanliness problems during curing. The weight and volume of washing media passing through the components result in a high level of cleanliness and subsequent rotation drain minimises carry over to the hot cure module.

Hot Cure

This takes place in a separate tank with water controlled at a minimum of 90°C (195°F). For maximum productivity, a rotational system is recommended, where the hot cure solution is pumped from the tank to the manifold at the top of the chamber. The solution fills the chamber to the point where it automatically weirs back to the lower storage tank. The method not only cures the sealant within the porosity but provides a very effective final washing action.