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Meter-Out Pressure Intensification Cures

Controlling a run-away load with meter-out flow controls normally causes intensified pressure on the rod side of the cylinder if the load is trying to extend the cylinder.

Taking the area ratio of the cylinder, (cap end area divided by the rod end donut area), multiplied by the system pressure on the cap end, will give the rod area pressure. An example would be a 3:1 area ratio, times a system pressure of 2000 PSI, resulting in 6000 PSI (PLUS what the load would add). See Fig. A.

Proper design would use a counterbalance valve with a meter-in flow control as shown in Fig. B. This will result in the rod pressure only being approximately 30% higher than what the load causes.

A fix for an existing system where it would be difficult to re-design: Add a pressure reducing valve as shown in Fig. C and set it to a low pressure. Again, the rod pressure would be a result of the load and the small cap end pressure.

Robert J. Sheaf, President CFC Industrial Training

Fig. A. Fig. B. Fig. C.

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