Pressure is expressed as force per unit area. In the SI system units of pressure are Pascals (N/m2) or Bar (=10 mPa). In Imperial Units, pound per square inch (psi) or lb/ft2.

Actuator force ratings are commonly based on 3,000 psi (207 bar = 20.7 mPa).
You can approximate the actuator area by dividing the force rating of the actuator by the pressure.

A = F/P

Imperial Units
A = square inches
F = lbf
P = lbf/square inches

SI Units
A = square cm
F = kN
P = .1kN/cm2 = 1 mPa

For dynamic applications some of the total system pressure needs to be available to move oil through the valve. Typically, for those applications force calculations (F = PA) are based on 2,000 psi (138 bar = 13.8 mPa)

Actuator Accessories
Swivel Bases and Swivel Rod Ends are actuator accessories which have a semi-spherical bearing with an adjustable preload mechanism. They reduces backlash in a test setup while maintaining the freedom to pivot.  Proper preload reduces friction, minimizes impact noise, and during load reversals encountered in high-frequency testing improves the waveform.

An actuator equipped with both a swivel base and a swivel rod end has the freedom to pivot at both ends. That minimizes moment loads on the piston rod bearings and load cell.

Spiral washers are easy to use devices, Spiral Washers preload elements of the load train to provide backlash-free connections. When placed over threaded studs, each half is rotated in opposite directions, placing a steady state preload on the stud. Typically they are used for attaching swivels and force transducers to an actuator..