move valve plug means 66 for example under the worst possible conditions there will be zero fluid pressure in the annulus 14 therefore the only forces affecting movement of operator means 42 and valve plug means 66 will be the fluid pressure force of control fluid and the respective forces of yieldable urging spring means 44 and resilient urging spring means 82 assume the safety valve 18 is positioned at a depth of 5 000 feet if the hydraulic control fluid is oil the hydrostatic control line pressure increases at a rate of 0 35 pounds per square inch per linear foot at 5 000 feet the hydrostatic control line pressure would be 1 750 psi if the valve plug means had an area of 0 05 square inches approximately a 0 25 inch diameter the hydrostatic pressure force affective upon valve plug means 66 would be 87 5 pounds approximately 0 125 cubic inches of fluid would be displaced upwardly in the control conduit 20 during movement of pilot valve plug means 66 from its second position to its first position the frictional fluid forces and force due to the inertia of the fluid would be relatively small therefore approximately 100 pounds of force would be required to assure that the pilot valve plug means 66 returned to its first position such a force may easily be provided with known coil compression springs.