Impregnation Equipment

 

The impregnation process, and thus the system offered, is often considered by many equipment suppliers as having limited scope for flexibility.

However, while the concept of impregnation may be simple, being based on clean, dry parts, followed by vacuum impregnation, draining, thorough washing and then curing, the level of sophistication and the process parameters required to produce effective, permanent results must be carefully considered.

Nowhere is this better understood than at Ultraseal, whose philosophy is not based on offering a customer a standard machine, but on assimilating a through understanding of the precise requirements and then providing a bespoke solution based on modular designs from a wide range of standardised elements.

For example, the requirements of a foundry handling raw castings will be vastly different to those of an end user seeking to impregnate finished machined components. Similarly, a sub-contract operation processing a range of parts of varying sizes and materials will have differing expectations from their impregnation facility than a manufacturer dedicated to just one component or family of similar parts.

Ultraseal's unique understanding of the varied requirements of customers in a diverse range of industries is clearly reflected in its client base and the enormous range components being impregnated worldwide today using Ultraseal impregnation technology.

 

The impregnation process involves five key stages:

 

• Part preparation
  
• Impregnation
  
• Drain
  
• Cold wash
  
• Hot cure

Process

PART PREPARATION
Before impregnation, porosity within the component must be completely clean and dry. While 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): here, the workload is suspended in a basket during the vacuum phase before being lowered and immersed in the sealant. The vacuum is then released, forcing the sealant deep into the porosity. VTS-based impregnation machines are simple in design and have a relatively small footprint.

Sealant Transfer System (STS): here, the workload is loaded into the autoclave with the sealant in an adjacent tank. After the 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 unused sealant returns to its original tank under vacuum. STS machines are simpler to automate and benefit from well conditioned sealant due to the length of time the sealant is held under vacuum. 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. Good draining is essential to reduce '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 features within more complex components. A rotational drain system physically rotates the components in their basket to maximise sealant removal. This is then collected and automatically returned to the autoclave.

 

COLD WASH
After draining, the components are transferred to the cold wash tank for removal of 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 affect a high level of cleanliness and the 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 a point where it automatically weirs back to the lower sump while the chamber is continually filled with filtered, reheated solution from the lower storage tank. This method not only cures the sealant within the porosity but provides a very effective final washing action.

 

Top Loading Machines

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. Simple top-loading 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 a modular approach allowing the provision of the most suitable, cost-effective solution.

 

Top Loader Sizes

 

 

 

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.

 

Front Load Machines

In various industries worldwide, there is an ever-increasing focus on integrated manufacture, increasing productivity while reducing costs and work in progress (WIP). This has placed an additional demand on impregnation systems, especially as conventional top-loading machines are not ergonomically suited to such requirements.

The adoption of 'lean manufacturing' by many companies represented a commitment to reduce WIP and the requirement now was for impregnation machines which could not only handle smaller batches but also offer faster cycle times and be fully integrated into the production process. Ultraseal International pioneered the world's first front-loading impregnation system to complement
the majority of manufacturing worldwide which is conveyor-based. These systems offer greater speed, control and significant health and safety advantages, as well as the key ability to be fully integrated into production lines. Where required, the impregnation system can now be connected to the previous operation by simple conveyor, negating the need for auxiliary transport mechanisms. Furthermore, the loading of each module is simplified, with no requirement for an overhead gantry or hoist.

These advanced modular systems offer high throughput with shorter cycle times, with each module
accommodating a smaller number of components and so minimising work in progress.

Ultraseal front-loading machines were from the beginning designed specifically to work with the company's acclaimed recycling sealants with all their associated environmental and health and safety benefits. They also have closed tanks, with process fluids remote and covered, minimising emissions into the work area, and so enabling them to be placed in the main part of the factory alongside other processes.

 

Each compact module offers all the productivity and quality advantages associated with rotational processing, while unlike top-loading machines, the rotational drain process takes place within the autoclave, reducing the number of modules required and so saving cost and floorspace.

 

Front Loader Dimensions

 

 

 

 

Front-loading machines are designed to accommodate standard Eurotrays or similar sized baskets to minimise workhandling. In many applications, the components are never handled at the impregnation system, being processed in their transportation carriers, removing the potential for component damage created when parts are transferred to and from baskets.

A further advance by Ultraseal has been the development of fully automated 'through' machines for complete integration into mainstream production, offering the high throughput required for high volume applications such as engine block manufacture.

Some machines have been linked into production lines whereby after machining, the blocks are leak-tested, with only those identified as requiring treatment diverted automatically into the impregnation machine. They are then leak-tested again to verify the success of the impregnation process before proceeding to the next operation. For quality assurance, other manufacturers elect to impregnate 100% of the production and indicate that the cost to impregnate can be less than the cost to pre-leak test.

 

 

What is Recycling Technology?

While conventional sealing technologies have made major advances in terms of quality and consistency, increasing concerns over the efficiencies and effluent impact of the process has led to increased research towards a more friendly and effective solution.

 

In traditional impregnation processes, up to 90% of the sealant consumed goes down the drain as effluent from the cold water wash tank. This is not only wasteful and adds cost to the process, but also brings a greater financial burden to bear on companies that are facing ever-increasing environmental legislation and concerns.The growing need for manufacturers to reduce bottom-line costs and address environmental issues led Ultraseal International to develop the world's first recycling sealant in 1987. This revolutionary sealant, offered all the qualities of conventional sealant but with the added commercial and environmental advantages of being recyclable.

 

Ultraseal recycling sealants are specially formulated to give them hydrophobic properties. They have a specific gravity less than 1.0 which means they will naturally tend to separate from water. The separation process involves the Sealant Recycling System (SRS). This is a custom-built separator that takes sealant-laden water from the wash tank and passes it through filters, before separating the sealant from the water.

 

 

 

 

The wash water solution is dosed with Ultraseal Wash Water Conditioner (WWC), which ensures separation of the sealant from the cold wash water. The recovered sealant is then returned back to the autoclave and the remaining wash solution is pumped directly backto the wash tank,giving a totally closed loop system. Unlike conventional systems, there is no requirement to change the cold wash water. Therefore manufacturers who use this system experience substantial cost savings through lower sealant consumption, conservation of water, reduced down time and in addition, less effluent and the associated environmental benefits.

 

Conversions of Existing Non-Recycling Machines to have Recycling Functionality

Ultraseal Internstional can supply both top and front load impregnation machines with an SRS to enable the use of recycling sealant. Existing non-recycling impregnation machines may be compatible but this would be subject to a site survey and inspection. Any machine conversions will be for the use of Ultraseal recycling sealants.