Fluid Power Journal

Problem: Cylinder Extension


  • Cylinder is 4″ x 20″ x 2″
  • Operating pressure is 100 psi
  • No load on cylinder

This cylinder is extending at a rate of 5 inches per second. If the piston seal develops a leak of 1 cfm, how fast will the cylinder extend?

Find Out The Solution

Note that this circuit is a metered-out circuit and that the pressure is higher at the rod end of the cylinder than the cap end, so the air will escape to the cap end to make the cylinder extend faster, not slower as one might think. The flow control remains the same.

1 cfm = 1728 cubic inches of volume

Volume =  area x stroke

Area of the rod end of the cylinder is the area of the cap end – the area of the rod end.

(4² x 0.7854) – (2² x 0.7854) = 9.4244 in²

Volume escaping is 1728 in3 / minute

1728 in3 / 9.4244 in² = 183.35″ / minute

183.35 / 60 = 3″ additional travel per second

3″ of leakage + 5″ per second normal speed = 8″ / second.

Deadline past. Not available for submissions.

By Ernie Parker, AI, AJPP, AJPPCC, S, MT, MM, MIH, MIP, MMH,
Fluid Power Instructor, Hennepin Technical College, EParker@Hennepintech.edu

This teaser is printed in the Fluid Power Journal. Those who submit the correct answer before the deadline will have their names printed in the Society Page newsletter and in Fluid Power Journal. The winners will also be entered into a drawing for a special gift.

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