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Sanitary Hose Assemblies: What is Minimum Bend Radius and Live Length?

May 5, 2014
Silicone Hoses Used as Jumpers on a Biological Skid

Silicone Hoses Used as Jumpers on a Biological Skid

Whether it is to unload a truck, transfer process fluids, serve as a jumper on a hot water jacket, or connect to a load cell, sanitary hose assemblies are everywhere.   We know. We assemble, test and ship custom sanitary  hose assemblies every day. We offer sanitary hose assemblies in a wide variety materials, including Teflon, platinum cured USP Class VI silicone, and food grade rubber.

After selecting the correct material and specifying your connection type, your next decision is hose length. There’s more to this decision than you might think and this post will take a closer look at two important factors when specifying a hoses: live length and minimum bend radius.

Minimum Bend Radius

Minimum bend radius is the minimum radius a hose can bend without kinking, damaging, or shortening the life of the hose. The minimum bend radius is measured from the inside curvature of the hose and the smaller the bend radius, the great the hose’s flexibility. In essence, the minimum bend radius is the radius below which a hose short not be bent.

The minimum bend radius is largely determined by two factors- hose material and size. Smaller hose assemblies will have smaller minimum bend radii than larger hoses. For instance, Saint Gobain’s SBP sanitary hose has a minimum bend radius of 1.55” in the ¼” ID size, while it has a 4” bend radius in the 1” size.

The second most critical factor in minimum bend radius is material. Silicone hoses tend to be more flexible than Teflon hoses and hoses that do not have a wrap or braid tend to be more flexible than hoses that do. There are exceptions to this rule, however. While our standard stainless steel braided Teflon hose has a minimum bend radius 12” in the 1” size, Aflex’s innovative, market leading BioFlex hose with a SS braid has a minimum bend radius of 2.75”, which is even more flexible than some silicone hoses.

Minimum bend radius is a crucial factor when deciding how long of a hose you need to accommodate directional changes in your process. If you’re just looking for a straight transfer sanitary hose, anything that is compatible with your fluid will work, but if you need a minimal amount of hose for a tight corner or U-bend, check the minimum bend radius before specifying a hose.

Live Length

The live length of hose is the amount of hose that falls between the two crimp collars. Because the crimp collars and fittings are made from either stainless or a rigid plastic, the live length of hose is the only part of a flexible hose assembly that will actually flex. While collar OAL with vary with both hose type and size, it’s important to remember that for a flexible hose to be flexible, it needs to be long enough.

Every day, we’ll have customer who want to use a 4” long hose assembly and we have to remind them that a hose of this length isn’t going to give them the functionality they expect. While there is no hard and fast rule on determining hose live length, a good way to check the minimum live length of hose is to check the minimum bend radius against the required offset for your application.

Another issue that dove tails with the live length issue is the hose’s “force to bend”.  While two different sanitary hose materials may have similar bend radii, one may take greater effort to actually bend the hose.  This can make a difference in functionality.  A short sanitary hose with a high force to bend may not be suitable for some load cell isolation applications.   Hoses with high force to bend requirements may prove more difficult in applications where operators are having to attaching and re-attaching the hose on a frequent basis.

 

Conclusion

To conclude, whether it is to unload a truck, isolate a pump, transfer process fluids, serve as a jumper on a hot water jacket, or connect to a load cell, sanitary hose assemblies are everywhere. While material compatibility is important, overall length and flexibility are also critical. Double check your hose’s minimum bend radius and make sure you have enough live length the avoid ending up with a rigid spool. If you have any questions about your sanitary hoses, contact a Holland Sales Engineer today.

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