As engine designs continue to advance, units become smaller, more complex, and increasingly reliant on new materials. While improving performance and efficiency, these changes have led to new concerns for engineers and manufacturers, as components that once were commonly-used are no longer appropriate.

The plugs used to seal fluid ports are a notable example of increased complexity in cost evaluation. In the past, balls, threaded screws and cup (freeze) plugs were often selected. These traditional methods – while offering a low cost per piece – are often inappropriate for new designs when installation, performance and warranty factors are evaluated. Engineered seals, such as the KOENIG EXPANDER® from SFC KOENIG®, often prove to be the most cost-effective choice.

Installation is often the first indicator of savings. Both ball plugs and cup plugs require boring, usually with a fine surface finish, as well as reaming. While a simple bore is acceptable for threaded screws, these components require thread tapping and surface chamfering. With each additional step in port preparation, process and labor costs increase. Comparatively, KOENIG EXPANDER plugs can be directly installed in a standard bore and require no counterboring.

metal-to-metal seal costs comparison chart
               A number of factors affect the total cost of a sealing solution.


Once installed in the hole, traditional seals require additional labor and processing. Ball plugs must be secured by deforming the housing after installation, and contamination generated during installation is a risk. Both cup plugs and threaded screws typically require the application of sealants. While this adds to process costs, the risk of contamination also increases, as excess compound and metal shavings can enter the fluid system. This can lead to critical performance issues for the customer and increased warranty costs for the manufacturer.

With its expansion design, KOENIG EXPANDER plugs create a secure and leak-proof metal-to-metal seal. The plug’s serrated expansion sleeve directly sets into the as-drilled bore walls, and no additional operations or sealants are needed.

expander plug installation can help lower total costs
The expansion design of KOENIG EXPANDER® plugs creates a secure metal-to-metal seal without sealant or extra machining, lowering process costs and the risk of contamination.

Error and scrap rates must also be evaluated. Ball and cup plugs utilize force-fit installation processes. Threaded seals apply rotational installation forces. These pressures can affect the base geometry, pushing into nearby passages and even creating cracks in the base. This can lead to scrapped parts, rework and potential warranty costs.

Misalignment more easily occurs with threaded seals and cup plugs. A threaded seal must carefully set in the port to avoid cross threading, and the small height of a cup plug can easily be inserted at an incorrect angle. An improperly set plug not only leads to errors, scrap and waste, but can decrease a seal’s long-term effectiveness – leading to leakage and warranty costs. Comparatively, KOENIG EXPANDER plugs apply even and controlled pressures, with process stability that supports strict requirements as well as thin wall applications.

Threaded screws and cup plugs are also difficult to integrate into automated assembly operations, leading to additional investment and labor. KOENIG EXPANDER plugs are widely proven in automated installations, and SFC KOENIG offers setting equipment that controls installation forces and distances. As production lines increasingly integrate IOT, automated process further supports and increases expander seal benefits.

KOENIG EXPANDER plugs offer a variety of models that can help lower costs
KOENIG EXPANDER® plugs often prove to be more cost effective when factors such as installation, performance and warranty are included in total value calculations.

While installation and rework costs are more easily calculated in seal value, long-term warranty issues can also have dramatic affects. Performance issues, damage and system failure have significant consequences and costs. With more than 5 billion parts installed and failure rates less than 1 PPM, the reliability of KOENIG EXPANDER seals is proven.

While traditional cost considerations often focus on the per-piece cost, modern designs and manufacturing environments require a detailed review of total costs when evaluating return. SFC KOENIG has created a calculator that easily allows users to compare their current solution to a KOENIG EXPANDER plug.

Learn more about SFC KOENIG expander plugs, or submit our quick Value Calculator form for a total cost comparison calculation, and learn how KOENIG EXPANDER plugs compare to your existing seal products.