Update on

February 27, 2010

Hydraulic Design & Consulting: Technical Notes

I Have Questions

Question: Why am I getting an  inaccuracy setting my valve on a test bench vs. in the system?

Answer: What you are probably seeing is the error that occurs as the flow is ramping up to the minimum rated flow. Below the minimum rated flow the valve does not see enough flow to operate correctly. You must bench test valves at their minimum flow rating to set the valve correctly.

Question: Why do you call it a hammer valve?

Answer: The valve was developed originally to power demolition hammers.  The hammers are aftermarket accessories that are mounted on a large variety of excavators.  The "hammer" circuit provides a method of tapping into the existing hydraulic system of the excavator, turning the tool on and off, controlling flow.

  

Every manufacturer of hammers has very specific needs as far as flow and pressure and there is a large disparity of hydraulic systems in the excavators.  Referenced from Sun Hydraulics.

Question: How big is a drop of hydraulic oil?

Answer: That depends on who is measuring the drop; everybody does it a little different. A safe bet would be about 16.6cc or about 250 drops in one cubic inch of oil.

Question: Can I adjust a counterbalance valve in the field?

Answer: It is always recommended that a counterbalance valve be set on a test bench before it is installed in an application. Correctly setting a counterbalance when it is installed is very difficult to near impossible due to the pilot assist and the interaction with the actuator.

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