Why does a pressure drop in a pipe cause a force on the pipe?

[sevn]

Hi,

I just started a course in drilling and the first chapter is about various situations where pressure drops in the drill string (pipe) causes forces on the pipe.

I understand that a pressure drop due to friction causes a downward force on the pipe. The fluid is "pulling" the pipe down.

However, when equipment in the pipe (such as a pump) is using energy from the fluid flow as its energy source, and there is a pressure drop due to this. Why is there a downward force on the pipe?

At the nozzle of the pipe there is also a pressure drop, which causes a downward force on the pipe. Again, why does a pressure drop cause a downward force on a pipe?

Hope my question is understandable :)

Thank you!

 

[jedishrfu]

Is the pressure working against gravity so that when it is less then gravity pulls the pipe downward?

From a picture of oil drilling it seems that the drilling mud is pushed through the bottom of the pipe so that the effect would be like pushing a water hose against a wall you would feel a push back and then when the water is shutoff you would hit the wall.