Density based mechanical valve control system

An apparatus comprising:

• a valve member;
• and
• a float member mechanically coupled via a mechanical coupling to the valve member and configured to operate the valve member, wherein
• the mechanically coupled float member is configured to increase flow through the valve member as a density of fluid decreases and to restrict flow through the valve member as the density of the fluid increases,
• the mechanical coupling comprises at least one of a linear spring and a radial spring configured to resist a buoyant force acting on the float member,
• the buoyant force generates a first torque applied to the valve member via the float member, the at least one of the linear spring and the radial spring generates a second torque opposing the first torque,
• the first and second torques balance to maintain a degree of openness of the valve member, and
• the degree of openness of the valve member is related to changing density of the fluid, and further wherein
• the apparatus is (i) more responsive to the changing density of the fluid when the valve member is closer to a fully open position, relative to when the valve member is closer to a fully closed position or (ii) more responsive to the changing density of the fluid when the valve member is closer to a fully closed position, relative to when the valve member is closer to a fully open position.