Near vertical position drifts slowly downward issue

One of the most common problems we hear is like a rod of ordinary single-cylinder, mounted vertically or nearly vertical drifting slowly downward after the directional valve is closed.

And a heavy burden lifted, the forces of labor, the cylinder down. But if ports are closed by valves, which blocked the flow path?

 It popular is that the piston seal is broken inside the cylinder and the movement of drift occurs because the fluid by gravity under pressure is forced by the piston. But is this possible?

Can a single rod cylinders really behave in this manner when the piston seal fails?

To answer these questions we need to consider some basic principles of volume.

Imagine a six-foot, 6 “diameter pipe closed at one end and sitting on a surface. Imagine that the hose is already filled with liquid. Then you come to drop with a length of 2 inch diameter rod in solid steel pipe open end at the top.
What happened? Liquid overflows and spills, because the pipe was already full. He was put in place over the line for the volume of steel in him and you because of the displaced liquid was left.
cylindermyth6

Now consider a vertical cylinder with the tip of the stem upward. Rod End gland and seal are in good shape.

Let’s start with the stem fully extended, and suppose that there is no air in the fluid under the piston. The cylinder is lifting a heavy load. Both the ground (barrel end) and above (rod end) will be closed ports ball valves.

If we now remove the piston seal, so there is a noticeable gap between the piston and cylinder wall, what will happen?
If the piston and rod assembly, or it will drift down in his seat?