I was recommended a book “Hydraulic Control Systems” by Herbert E Merritt. Although the maths flies gently over my head there is some very interesting stuff for the Hydraulic enthusiast.
I recently asked a question about grooves in pump pistons and valve spools and what was their purpose. I found the answer and I will try to explain in my own Layman’s language.
With close tolerance pistons it is possible for hydraulic forces to create lateral movement on the piston forcing it to one side of the bore. This can cause stiction (hydraulic lock), extra leakage and a trap for contamination.
Just one groove on the piston can reduce the lateral forces by up to 40%. The grooves create a centreing effect and help prevent metal to metal contact between piston and bore. Adding more grooves will also be beneficial.
The depth and the width of the groove should be 10 times the clearance and the sides of the groove should be perpendicular to the bore.
Ref from Hydraulic Control Systems
More stuff on www.hydraulicbrain.com
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