12. What's the difference between balanced and unbalanced valves Outlet balancing is required for proper valve functioning in those applications where the outlet pressure is more than 25% of the inlet pressure. When the outlet pressure is relatively high compared to the inlet pressure, the normally closed poppet will sometimes be pushed up off the internal orifice by the back pressure on the valve. Outlet balancing prevents the backpressure from acting on the poppet. 13. How do the characteristics of the actuator influence the control valve operation? The valve and actuator are engineered to work together. Most manufacturers provide an anti-hunting algorithm in the valve that prevents the valve from modulating until it exceeds the tolerance of the valve. Use spring-loaded diaphragm type actuators where practical. Spring-less operators and cylinder operators are acceptable only when spring-loaded diaphragm type actuators cannot provide the desired performance. Select the actuator so that the valve or damper that it controls will fail safe. Fail safe is defined as lock in position or take a position (either open or closed) that will result in the least upset.
