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DOM Hydraulic Tube

DOM Hydraulic Tube

DOM Hydraulic Tube

(OP)
Hello,
I am looking to replacing our J525 hydraulic tubing with DOM tubing in certain applications.  The primary reason is material strength.  We have had issues with pressure line failures likely due to pressures >7000psi.  We can't increase the wall thickness of the J525 tubing because our flow velocities go above the recommended values.  There are other limitations that prevent us from increasing the OD and then wall thickness.

My question is how do we ensure our vendor supplies us with clean DOM tubes?  What is the standard way to present a cleanliness specification?

I have read in SAE J1227 that we should specify a "cleaning" Reynolds number at least as high as the value seen during normal operation.

I received information from a vendor that states cleanliness in particle size/count/patch.

Do we need to specify both?  Is there another method?

Thanks,

Nick

RE: DOM Hydraulic Tube

In this case my advice to you would be...

If you have enough power to handle the increased pressure drop, increase the wall thickness.

The blind recomendations on flow velocities are there for consideration only, they will have an effect on the performance of the system but they will not ultimately govern how the system functions.

On smaller tubing, increasing the wall thickness can increase the working pressure by 50% with no appreciable increase in flow velocity.


If you do need to specify a cleanliness level for the fluid, it is usually as follows. These codes are approximate.

ISO 4406 Code for Unfiltered oil          - 19/16
NAS 1638 code  "       "                  - 10

ISO 4406 code for new oil                 - 17/14
NAS 1638 code  "       "                  - 8

ISO 4406 code for clean filtered oil      - 14/12
NAS 1638 code  "       "                  - 5

The best way to obtain more information about cleanliness codes and oil contamination is to use an internet search engine to search for "ISO 4406".

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