Oetiker ear clamp technical selection guidelines

Mechanical hose barb connections consist of a hose barb, flexible tubing and a retention device. Retention devices are generally placed closely behind the barb and are used to improve the connection’s pull-off strength and pressure resistance. Oetiker® clamps are commonly used retention devices.

When sizing an Oetiker® clamp, the hose barb and tubing dimensions are critical in the selection process. Qosina has developed helpful Oetiker® ear clamp selection guidelines to help you determine the appropriate size for your application.

The hose barb dimensions of the major OD and the shaft OD (Image 1) need to be considered in combination with the wall thickness (WT) of the tubing (Image 2). The WT can be calculated using the following formula if only inner diameter (ID) and outside diameter (OD) are known.

Weight equals OD minus ID divided by 2.

Each Oetiker® clamp has an established diameter range (closed to open). The OD of a hose barb connection is measured or calculated. This is the Tubing OD on Shaft measurement. This is where the clamp will be installed, and the size must be slightly above the average value of the diameter range of the clamp to be selected. The Tubing OD on Shaft is calculated as follows:

Tubing OD on Shaft=Shaft OD+(2*WT)

The Tubing OD on Barb dimension is important, as it impacts how the Oetiker® clamp gets installed. In most cases, the clamp’s open diameter is larger than the maximum OD of the assembled hose barb and tubing, allowing the Oetiker® to be placed on the tubing prior to hose barb insertion. For some larger barbs, the major OD is significantly larger than the shaft OD, such that the clamp open diameter is insufficient to pass the clamp over the barb after insertion. In this case, the Oetiker® clamp must be positioned on the hose barb before insertion into the tubing. The Tubing OD on Barb is calculated as follows:

Tubing OD on Barb=Major OD+(2*WT)

After installation, the compressive force of the sized Oetiker® clamp must not damage the hose barb or tubing, which can compromise the connection. A closing force must be identified and further qualified through dimensional evaluation and experiment to ensure the required material compression. The harder the tubing, the higher the required closing force to ensure appropriate compression. The necessary closing force is greatly reduced when compressing a soft material. After identifying closing force and ensuring appropriate compression, qualification of the hose barb connection through functional testing is recommended to ensure connection performance based on defined specifications.

Proper closing force and percent compression is best determined through experiment. Qosina, in collaboration with Oetiker® technical support, is available to help identify the recommended clamp and closing force for a specific hose barb connection via testing. Samples of the tubing and hose barb connector would need to be provided. Please contact sales@qosina.com to initiate a request.

Percent tubing compression of a fully closed Oetiker® clamp is calculated using the following equation. This will be helpful in the Oetiker® selection process by eliminating clamps under the recommended compression range.

Percent Tubing Compression equals Tubing OD on shaft minus maximum closed clamp ID divided by 2 multiplied by weight multiplied by 100.

Identification of the closed dimension at a specific percent tubing compression can be calculated to help confirm clamp selection. This value should be slightly larger than the maximum closed diameter of the selected clamp.

Closed Dimension at X% Percent Tubing Compression = Tubing OD on shaft – [(X%)*(2*WT)]

Below is a guideline on the recommended compression ranges by tubing type:

Tubing TypeRecommended Compression Range
Soft Silicone (Durometer, Shore A: >50) 15-20%
Silicone and TPE (Durometer, Shore A: 50-60) 20-30%
Braided Tubing 25-30%

Confirmation that the assembly of the selected Oetiker® clamp and installation tool is not hindered by interference is required.

How to select an Oetiker® clamp on Qosina’s website

Visit qosina.com and explore our extensive selection of Oetiker® clamps.

Clamps are sorted by default based on size (based on their closed diameter). Additional filters are available based on product attributes to allow for easy sorting by product features. These include clamp type, series, process option, open diameter range, closed diameter range and band dimension (where available).

Tubing:Hose Barb:
Size: ½ inch ID x ¾ inch OD Shaft OD: 0.555 inch
Wall thickness: 1/8 inch (0.125 inch) Major OD: 5/8 inch (0.625 inch)
Material: Platinum-Cured Silicone  
Durometer: 50 Shore A  
Tubing OD on Shaft=0.555+(2*0.125)=0.805 inch Tubing OD on Barb=0.625+(2*0.125)=0.875 inch

To provide optimal compression, the selected clamp should have a closed-open range with 0.805 inch slightly above the average value. For installation purposes, ideally the open diameter would be larger than 0.875 inch.

The filtering options on the website allow for fast and easy identification of potential clamp(s) using the following search criteria:

Clamp type StepLess® Ear Clamp
Process option Degreased
Open diameter range 0.788 - 1.181 inch (>20 - 30 mm)

There are two potential clamps that are identified based on initial calculations/measurements:

16701029 0.701 Inch Closed - 0.827 Inch Open Range (17.8 mm - 21 mm)
16701041 0.764 Inch Closed - 0.89 Inch Open Range (19.4 mm - 22.6 mm)

The closed clamp dimensional range for the recommended 20-30% compression can be calculated, which is 0.730 – 0.755 inch. This indicates clamp 16701041 with a maximum closed dimension of 0.764 inch will have a maximum compression less than 20%.

Closed dimension at 20% percent tubing compression = 0.805 – [(20%)*(2*0.125)] = 0.755 inch Closed dimension at 30% percent tubing compression = 0.805 – [(30%)*(2*0.125)] = 0.730 inch

Estimated tubing compression at full clamp closure:

Clamp 16701041

Percent Tubing Compression equals 0.805 minus 0.764 over 2 times 0.125 multiplied by 100 equals 16.4%

Clamp 16701029

Percent Tubing Compression equals 0.805 minus 0.701 over 2 times 0.125 multiplied by 100 equals 41.6%

Clamp 16701041 is under the recommended compression for the tubing selected but could provide a reliable connection depending on the application requirements and would allow for easy installation over the barb.

Clamp 16701029 complies with compression recommendations, but with an open diameter smaller than the Tubing OD on Barb measurement careful installation of the clamp is warranted.

Once clamp(s) are identified, testing can be performed to confirm the required closing force to achieve proper tubing compression. Once defined, functional testing with several assemblies is recommended to ensure the connection meets the requirements of the application.

Oetiker® samples:

Quick and easy sampling is available on the Qosina website. Up to five clamps can be requested using the “Sample Request” button on the product page.

If the identified clamp needed for your application is not currently available on our website, please contact us as at sales@qosina.comand we can provide a quotation for the desired product.

Hand Installation Pincers (HIP) Cordless Clamp Pincers Pneumatic pincers Electronically Controlled Pneumatic Pincers Hand Clamp Cutters

Oetiker® assembly and disassembly tools

  • Oetiker® assembly tools are used to close the clamp by drawing together the lower radii of the “ear.”

    • Installation Pincers (HIP) are typically used for low volume assemblies, assembling in tight spaces or for field service activities. They are available in single and compound action versions, with the compound action requiring up to 30% lower hand forces during closure with the ability to close a wider variety of clamps and sizes. The compound action pincer with side jaw is designed for tight space constraints.
    • Cordless Clamp Pincers generate precise clamping force and allow for installation flexibility. The PC software that accompanies it allows for adjustments of closing force, tool testing and retrieval of historical data.
    • Pneumatic Pincers are best suited for high-volume assembly and ensure repeatable closure force after manual calibration. They are lightweight, designed for one-handed operation, have a paint-free body to avoid particulate contamination and are available with medical-grade lubricant.
    • Electronically Controlled Pneumatic Pincers ensure process reliability through electronic monitoring of parameters ensuring repeatable closures based on qualified parameters. They can be fully integrated into automated systems and allow for documentation availability. They have internal calibration and allow for pre-programmed settings.
  • Oetiker® disassembly tools are used to safely remove ear clamps.

    • Hand Clamp Cutters are designed for quick and easy clamp cutting and are for the removal of ear clamps. Designed for many cutting cycles, their solid metal construction ensures long tool life without performance loss.

For more information on creating a secure hose barb connection, please refer to our blog, “Everything you need to know about creating a secure hose barb connection.”


  • Bioprocessing Equipment, ASME BPE-2022, 2022
  • Oetiker® Product Guide, Oetiker®, 2016

This information is intended to be a guide; you must determine fitness of Products for use. While Qosina may be assisting you with clamp size selection, it is understood that you assume all liability and responsibility for selection and use of Products by you and/or by any third party that purchases or receives the Products (or products incorporating the Products) from you or your transferees. Qosina is not and shall not be liable or responsible in any way for any such selection or use. The Products are intended only for further manufacturing or assembly and you are responsible for testing the products in your intended use. Exposure of Products to other materials, chemicals, sterilization or temperature extremes may cause changes in material from which the Products are manufactured, which may make the Products unsuitable for use.