Hi Folks,

Application : We are testing an auto component for fatigue loading, by loading a D.A cyl, 100 mm bore, (being used as a single acting one) by pressurizing the piston side upto 150 bar. The pump is a Dowty fixed disp gear pump, 20 LPM. The cyclic pr cycle of 20 to 150 bar is achieved by varying voltage level signal between 0-10 VDC on the Vickers make prop relief valve. The cylinder disp is 5-6 mm for this pr cycle.

Problem : At a constant voltage of 10 V, we get pr of 150 Bar being measured by pr transducer and displayed on monitor. However as we cycle the valve with sine wave signal of 0-10 V with increasing freq of 1 to 4 Hz, we no longer reach 150 bar but the pr amplitude decreases to 110, 90, 70 & 50 bar at 1, 2,3 and 4 Hz resp.
The relief valve is mounted directly on the cylinder with min trapped vol of oil. How best can we increase the pr amplitudes at higher freq ? How can we calculate or predict this decrease in pr amp beforhand. Please throw some light.

Best Regards.

I would try setting pressure at 10V at a higher pressure than your target so the valve would be giving target pressure at a lower voltage. This would allow the feedback to control max pressure not the saturated coil.

Just a thought.

If that is no help you probably need a Servo Valve to get the response you desire.

Hello Mr Bud Trinkel,

Yes, you were spot on! The problem indeed was the gain setting on the valve card and the fact that the card preffered power supply of 24 VAC instead of readily available 24 VDC.

This greatly improved the pr levels but still we are getting about 120 bar max level at 4 Hz against the desired of about 150 bar.

In our application we use the reactive force of the component to push the cyl rod up. What if we use the cylinder as double acting and use instead a prop DCV? Will it help improve the freq response and pr amplitudes?

Thanks & Regards.
Shailesh Nigudkar.
Polymech Systems, India.