Measuring the Hold Up Volume in Sanitary Hoses

Holland has been assembling and selling pharmaceutical grade sanitary hose assemblies for over 15 years. One of the questions we are constantly asked is, “What is the potential hold-up volume of liquid in the hose?”

The standard design for crimped-on hose fittings leaves a step in the ID of the hose where the barbed insert ends. This step ensures there will be some amount of liquid retained in the hose, but how much? Sanitary hoses with flare through ends are supposed to alleviate this condition but they are expensive and only available in Teflon material.

Since none of the hose manufacturers publish this hold up volume data, we decided to do our own testing. We built a test rig that would allow us to test the drainage of hoses at various angles. Our test methodology consisted of pouring a known volume of water through a series of 1 ½”ID hoses, then capturing and measuring what drained through. The liquid volume draining from of the hose was compared to the input into the hose to determine the hold-up volume. The results are listed below.

Fluid Retained (mL) in Teflon Hoses at Various Drain Angles of 1 ½” Hose

Drain Angle (Degrees)Teflon Hose Crimped EndsTeflon Hose Flare Through EndsTeflon Hose No End
341.11.15
530.51
7.510.10.9
10100.3
12.5100
200.500
300.500

Conclusion

If your hose is going to be at a 7.5 degree drain angle or higher, the type of end connection used will not affect the hold-up volume. At that angle, the only retained liquid in any of the hoses was a function of surface tension. Below 7.5 degrees, the flare through style end connections drain better.

So which end connection do you choose? The hold-up volume on crimped end type hoses is minimal. They are less expensive and available in a wider range of materials, including Teflon, silicone and EPDM. In many cases they are an excellent choice. But, if you are dealing with a high value product and want to ensure you get complete drainage, flare through hoses might be a better choice. While flare through type ends offer better drainage, some applications are not well suited for these hoses. Over-tightened sanitary clamps and SIP applications may sometimes cause problems for flare through type ends. The flare through design is expensive and offered only in Teflon. But they do offer more complete drainage.

© 2010 Holland Applied Technologies, Inc.


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