Quite often we receive questions from our customers that are relevant either to others in our network or of interest to other visitors to our site. Here you will find the answers to those questions and information on the various features of our extensive product portfolio and its application in industry.

If the answer is not here then please send us your query using our Contact form. We are always happy to answer any question concerning sealing and flow control technology.



SFC KOENIG is a global provider of products and solutions for sealing and flow control. Our core applications are in the transportation sector, in fluid control technology and precision engineering. We have main logistics centers in the United States, China and Germany, and our headquarters is located in Switzerland. With two production sites – in Switzerland and in the US – we are able to provide the highest level of service and efficiency. In addition, we have numerous distribution partners around the globe. More on our Global Presence.


The roots of SFC KOENIG lie in a flexible and innovative company, which was founded by Dr. Max Koenig, who received his PhD in Engineering in 1927. The company was originally focused on sheet metal processing, though throughout the years its capabilities and products expanded. In 1985, it was renamed KVT-Koenig AG. In 2014 the company again changed its name and brand to SFC KOENIG, to better reflect its position as a provider of the world’s leading sealing and flow control solutions. The company is proud of its successful and innovative past, and is excited about the future.


Our contact form can be found in the upper section of the website. In addition to standard information, please provide as many details as possible regarding your project so one of our engineers can assist you. We will contact you within one business day after form submission.


SFC KOENIG is the new identity of KVT-Koenig. Even though we have changed our name and logo, our focus and our commitment to providing superior engineering solutions for sealing technology and control systems remains the same. Our new name supports our position as the world’s leading supplier of sealing and flow control solutions.


Compared to other expander seal options, KOENIG EXPANDER® plugs provide unmatched reliability and a track record of superior performance, helping customers improve the total value of their sealing solution. The original inventor of the one-piece expander seal design, SFC KOENIG® utilizes advanced, automatic manufacturing technology to produce parts with precise capabilities. With over 5 billion parts installed,  KOENIG EXPANDER plug products are proven to successfully perform even in installations with vibration, pressure spikes, contaminants, and harsh operating environments. KOENIG EXPANDER plugs support temperature tolerances which surpass many other seal options, with operating temp ranges from -40°C to 150°C (-40°F to 302°F). Our seals are also available in a wide variety of standard material options and plug sizes, and can also be custom-developed to meet your specific application requirements.


Expander plugs feature a serrated sleeve which expands into port walls during installation, forming a secure metal-to-metal seal without the use of chemical sealants or compounds. The original inventor of the one-piece expander seal solution, SFC KOENIG® offers two styles of expander plugs: push-style expander plugs and pull-style expander plugs. Push style plugs utilize an integrated ball to expand the serrated walls of the plug into the base material, and require a counter-bore drilled hole. Pull-style plugs utilize an integrated mandrel, and are ideal for angled channels, deep hole installations, and do not require a counter-bore. While each expander plug design offers distinct benefits based on installation location and system configuration, both provide unmatched reliability, with failure rates less than 1 PPM, flexible tolerance allowances, and proven performance in a wide variety of critical applications.

Are SFC Sealing & Flow Control components RoHS compliant?

All SFC Sealing & Flow Control components and tooling equipment are RoHS compliant. The plating applied on the carbon steel plugs is Zinc-Iron, Clear Trivalent Chrome.

Are SFC Products DFAR compliant?

SFC products are standard commercially available catalog items.  If DFAR is absolutely necessary, further investigation would be required based on the part number.

What is the hole tolerance requirement for the SFC EXPANDER plugs?




What is the installation force on the product?

The installation force of the product varies by the size and materials, and other factors such as tolerance stack up, etc. SFC does not recommend installing by force but rather by distance, install force can be provided on a case by case bases for reference in sourcing adequate installation equipment. Installation Instruction MB PDF.

How to achieve the roughness of Rz = 10 – 30 microns?

With hard base materials like steel, titanium, cast iron the hole roughness should be from Rz = 10 – 30 microns. A normal drilling process with no secondary process of reaming or finishing the hole is recommended.

What is the roundness requirement for the holes?

The holes must be round within 0.05 mm or 0.002 inches. See catalog design guidelines.

What should be the hole conditions?

  1. The drilled hole must be within the specified tolerance
  2. The counter bore hole for the ball style plugs must be properly sized for the through hole (d3) according to the dimensional sheet in the catalog
  3. Holes must be round within 0.05 mm or 0.002 in
  4. With hard materials the bore roughness should be from Rz = 10 – 30 microns for best results, especially in harder materials.
  5. Longitudinal rifles and spiral grooves should be avoided
  6. The bore must be free of oil, grease and chips


Can I use Loctite® or any other type of sealant or adhesive on the outside of the product?

No, secondary sealants of any type are not recommended. SFC EXPANDER components achieve sealing through metal to metal contact and hence the part and the hole must be free of any substance, including sealants or machining oils.

How much force should I apply to install SFC EXPANDER push-style products?

SFC recommends controlling the stroke of the EXPANDER element while pressing. There is naturally a much larger variation in the force, and the stroke provides the most consistent method for controlling the installation of the plug.

How much temperature can the products withstand?

As a part of the qualification process, the products undergo a temperature-pressure cycle test. SFC products are tested and rated for -40°C to 150°C. Click here to view.

Can the EXPANDER plugs seal gases?

The EXPANDERs are designed & rated for sealing fluids, but they have been used in various applications to seal gases. Inquire with our application engineering team to review your requirements for sealing gases.

Can the EXPANDER products be subjected to heat treatment process after installation?

We recommend installing the EXPANDER plugs after the heat treatment of the housing. It is also recommended to mask the port where the EXPANDERs will be installed before heat treatment.

Can I apply sealant, adhesives or any compounds on the outside surface of the EXPANDERs for additional sealing performance?

The EXPANDERs are based on the metal-to-metal sealing principle. The outside surface of the EXPANDERs must be free of any sealants, adhesives or compounds. Applying any compounds reduces the sealing performance of the plug.

What is proof pressure rating?

Occasionally within hydraulic systems there are pressure spikes due to system variations. The proof pressure rating of the product indicates the maximum pressure spikes acceptable.

What is working pressure or nominal pressure rating?

The working pressure rating of the plug indicates the continuous pressure that the EXPANDER product can withstand over long term. The EXPANDER component can also withstand higher pressure spikes during the course of its lifetime, provided these spikes are temporary and not frequent.

I do not have room for a counter bore or enough bottom wall thickness, can I still use the push style EXPANDER products?

It is recommended to use the pull style EXPANDER plug (SK or LK). If for other reasons you have to use the push style EXPANDER then it is recommended to use a pin or provide some fixture from the bottom to support the forces acting on the product during the installation and insertion of the EXPANDER element.

Can I use the EXPANDER products in softer materials like aluminum?

The EXPANDER products can be used in the softer materials like aluminum. During the expansion of the body the grooves on the outside surface bite into the softer material to create a mechanical seal and provide anchorage. See catalog anchorage principle.

Can I use the EXPANDER products in harder materials like steel, cast iron?

The EXPANDER products can be used in harder base materials like steel, cast iron. It is recommended to have a surface finish of Rz 10 – 30 microns. During the expansion of the body the grooves on the outside surface create mechanical locks with the rough base material at the microscopic level to create a mechanical seal and provide anchorage. See catalog anchorage principle.

Can I remove the EXPANDER element from an expanded component and then re-insert another EXPANDER element to reuse the component?

It is not recommended to remove reuse expanded component. The entire component (EXPANDER element & body) should be removed together. The bore should be inspected and drilled to the next larger size if necessary, and then install a new EXPANDER component. Plug removal is under the installation instructions (see comments above).

What are the advantages of using an EXPANDER plug over a threaded plug?

There are several advantages:

  1. Using the EXPANDER plug eliminates the thread cutting operation in manufacturing. The EXPANDER plug is installed in an as-drilled counter bore and does not require any special finishing process of the hole.
  2. Contamination and cleanliness issues are eliminated since thread locking adhesive or sealants are not needed. The EXPANDER plug anchors in the base material and provides a metal to metal seal.
  3. The expansion anchorage principle of the plugs prevents any back-out or loosening even in high temperature and high vibration environments.
  4. The installation of the EXPANDER plug is suitable for high volume production. There are no scrap or issues with thread misalignment or cross-threading.
  5. EXPANDER plugs take up less space than typical threaded devices, especially o-ring boss plugs. Designers save space and weight when choosing an EXPANDER plug


Do you have videos to show the installation and functioning of the EXPANDER products?

Please find helpful videos on our website here: Engineering Videos

Can I install the EXPANDER products in anodized holes?

It is recommended to mask the hole during the anodizing process and then install the EXPANDER product. The sealing could be compromised if the EXPANDER is installed in the anodized hole, due to the risk the hard anodized surface will crack under the stress of expansion.

Which industry accepted Quality standards is SFC certified to?

It depends on the SFC location specifically, find our certs here

  1. In the US, SFC KOENIG LLC is certified for IATF 16949 and ISO 9001.
  2. In Switzerland, SFC KOENIG AG is certified to IATF 16949, ISO 9001 and ISO 14001
  3. In Germany, SFC KOENIG GmbH is certified to ISO 9001 and ISO 14001
  4. In China, SFC KOENIG Flow Control is certified to IATF 16949 and ISO 9001


What should be the final position of the EXPANDER element in the push type EXPANDER products after installation?

The EXPANDER element must be pressed until the top surface of the element is flush or slightly below the top surface of the body/sleeve. Please refer to ‘x’ dimension in the SFC KOENIG product information.

What is the fit of the plugs before installation?

All the EXPANDER products are designed to be a slip fit. The EXPANDER product can be simply placed into the hole with no mechanical interference.

What is the roundness requirement on the hole?

The hole must be round within 0.05 mm. See catalog design guidelines.

Can you share 3D CAD files?

The 3D CAD files for SFC products are available on the SFC KOENIG website for download here. The files can be downloaded in many different formats.

Should the plugs be cleaned or de-greased before installation?

SFC products are delivered ready for installation. However, if the product is already in an open package in a relatively dirty environment cleaning may be advisable. It is recommended to only spray clean and air dry. Do not submerge in any solution or vacuum dry, which could affect the integrity of the assembly.

How can the ball style EXPANDER plugs be removed?

The plug can be drilled out with a carbide tipped drill of a high-speed drill. After removal of the plug always re-inspect the hole to be sure it is within technical specifications and drill out to the next larger size plug if necessary. Plug removal is under the installation instructions (see comments above).

What is the hole roughness requirement for harder base material?

The hole roughness requirement is Rz 10-30 microns.

  1. At a roughness greater than Rz=30 microns leakage might occur.
  2. If the hole is too smooth the EXPANDER product may not sufficiently anchor into place.

See catalog anchorage principle.

What is the difference between Ra and Rz surface call out?

The Ra measures the average roughness while the Rz measures height of the peaks of the surface. Since peaks within certain range are desirable for a mechanical sealing we specify the surface roughness by Rz.

What is the minimum wall thickness required around the EXPANDER product?

Please refer to the SFC KOENIG catalog or website for a simple formula to calculate the minimum wall thickness. The minimum wall thickness is dependent on the base material, plug style and the OD of the plug being used. Tech Info Guidelines.

How are the EXPANDER products tested?

There are two type of tests SFC engineering regularly performs:

  1. Test A: Static pressure test. The plugs are subjected to continuous increasing pressure until failure. The recorded failure pressures should be above the threshold. This blowout pressures has a factor of safety from the rated working pressure of the plug. Each batch of the plugs go through this verification testing.
  2. Test B: Temperature/Pressure Cyclic test. The plugs are subjected to cyclic temperature (-40°C to 150°C @ 2-hour frequency) and cyclic pressure (0 bar to rated proof pressure @ 2 min frequency) for a total of 168 hours. The plugs are expected to withstand these conditions without any leakage or blowout. This long-term test simulates the application conditions.

Click here to view.

Can we get dimensional information of the plugs?

Technical details can be found on the SFC website, here.

What is the plating specification on the carbon steel ball style EXPANDER plugs?

Type III, Clear Trivalent Chromate per ASTM B633.

What is the plating thickness on the carbon steel ball style EXPANDER plugs?

The plating thickness is between 2-7 microns.

Can you provide IMDS certificate for your products?

We can provide the IMDS certificate for the products. We will need your company IMDS code to send it through the system.

Are SFC Sealing & Flow Control components REACH compliant?

All SFC Sealing & Flow Control components are REACH compliant. Corresponding REACH declaration is available upon request.

Can I use the EXPANDER products in plastic materials?

SFC does have some applications in plastics and reinforced fiber-glass materials. Such applications require special consideration and can be developed upon request. Inquire with our application engineering team to review your requirement.

Can I use the EXPANDER products in brass materials?

SFC does have some applications in brass materials. It is recommended to use plugs with a stainless steel sleeve due to potential galvanic corrosion. Such applications require special consideration and can be developed upon request. Inquire with our application engineering team to review your requirement.

Can I use a hammer to install the EXPANDER products?

Small quantities or single parts can be installed with a hammer and a setting tool. For series production it is recommended to use a press.

Can I use the MB setting punch to install CV products?

The MB punch can be used for the installation of CV products and vice versa (see catalogue specification).

Can I use non SFC setting tools to install EXPANDER products?

It is always recommended to use original SFC tooling. SFC does not accept any liability for incorrectly processed EXPANDER products by using non SFC tooling.

What is the passivating specification on the MB600 stainless steel ball style EXPANDER plugs?

Passivated acc. to ASTM A967M-17

Design Support

Our expertise is at your service. Speak to our engineers for complete design-in support of our sealing and flow control solutions.


Our sealing and flow control solutions comply with global quality assurance and certification standards.