Pneumatic vs Hydraulic Controlled Direct Shear Machines

[RobPE]

Is there an advantage to hydraulic vs pneumatic controlled direct shear test machines?

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Section 6.4 of ASTM D5607 states that for maintaining the Normal Pressure: “hydraulic component that will hold a pressure, within 1%”.

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For shear displacement, Sect 8.6.2.2, no explicit hydraulic requirement(s).

Our labs utilize pneumatic machines, and per ASTM, verbatim, we are out of spec. We have considered converting to hydraulic because of this, but we would we be adding value to the testing with this time consuming and non-trivial project or are we meeting a requirement that does not result in a real benefit to the testing results?

 

[EireChch]

My gut says it doesnt matter much!

But can you not get a load cell and see how well you are holding pressure. If you are within 1%, whats the issue.

 

[RobPE]

Thanks for the reply. We do plan to do this. I'm anticipating that our machines will be within the tolerance, but nevertheless, my concern is not meeting the ASTM spec. We've had requests for specifically hydraulic-controlled loading. Wondering if you've encountered this.