Operationally, the main difference between a control valve and a regulator is that regulators are better defined as process powered valves without the demand for external power or even an instrument air source to operate. In the simplest terms, a valve controls flow and a regulator controls pressure. Since the use of process fluid pressure is a means for control, regulators are functional as pressure control valves.
Another difference comes in relation to the design pressure rating of the body of the regulator. Control valves are able to handle the same pressures on the output as they are on the inlet side. However, a regulator may have a lower pressure rating on the control pressure side (P2) of itself (the regulator). One more difference is speed. Compared to control valves, a regulators speed of response is faster. The regulator is able to respond to changes downstream instantly to correct the controlled pressure.
Control valves, however, are available in larger sizes and (generally) higher pressure classes than regulators are.
Regulators, usually, are associated with a lower cost for maintenance and installation. But it is also important to keep in mind that many projects spec in the use of an actuator with its valve for their control applications. Regulators can be used as a pressure-reducing valve, back pressure regulator or differential regulation because they can be configured to sense pressures from various locations directly as well as respond more quickly to any changes.
The main operational difference between a control valve and a regulator is that, contrary to the control loop design mentioned above, regulators are process-powered valves without the need for an external power or instrument air source to operate.
Another difference is that the speed of response is faster for regulators compared to control valves. To reduce droop and maximize accuracy, a pilot-operated regulator can be used. These regulators require only 1–3% droop or deviance from set-point to achieve full capacity. Direct-operated regulators need 10–20% droop. Pilot-operated types achieve this accuracy by adding a small, direct-operated regulator (the “pilot”) to the main regulator, which introduces gain to the system and increases sensitivity to changes in the controlled pressure. Pilot-operated regulators have much larger orifices as well, which allows higher capacities as well as heightened accuracy compared to self-operated regulators.
When choosing between a regulator and a control valve, design considerations outside of the process data itself need to be considered. For example, if diagnostic monitoring or predictive maintenance feedback are required, a control valve that can communicate diagnostic data to a control system should be considered. On the other hand, if the valve’s operation is critical to the facility, a regulator would be the more appropriate choice because auxiliary power is not required to maintain its functionality. other transducers can be added to the regulator setup to report diagnostics, as well.
While maintenance and total installed costs are typically lower for regulators, project specifications or site standards may require a control valve.