Valve positioner having bypass component and control valve comprised thereof
View Patent ↗A valve positioner that can maintain operation of the control valve despite failures in one or more components. The valve positioner may reduce downtime by allowing in-situ repair to occur on the valve positioner. The valve positioner may incorporate a by-pass component, which can utilize control input signals (e.g., a 4-20 mA signal) to energize one or more components (e.g., a current-to-pressure converter) to cause the control valve to modulate fluid flow without the digital microprocessor and/or related components.
1. A circuit for use in a valve positioner to control operation of a valve, the circuit comprising:
a processor;
a switch coupled with the processor to receive an input power signal and an operating signal from the processor; and
a current-to-pressure converter coupled to the switch,
wherein the processor is operative to:
receive a feedback signal having a value that defines an operating parameter for the valve, and
generate the operating signal having a level corresponding to the value of the feedback signal,
wherein the switch is operative to change between a first state and a second state in response to the level of the operating signal so as to conduct the input power signal to the current-to-pressure converter from the processor in the first state or from a source different from the processor in the second state.
2. The circuit of claim 1 , further comprising:
a signal conditioning component coupled with the switch, the signal conditioning component operative to,
receive a control signal from a remote device;
generate the input power signal using the control signal, the input power signal having properties to operate the current-to-pressure converter.
3. The circuit of claim 2 , wherein the signal conditioning component is configured to modify the control signal so that the input power signal has analog properties.
4. The circuit of claim 1 , further comprising:
a sensor that provides the feedback signal corresponding to position of the valve.
5. The circuit of claim 1 , further comprising:
a sensor that provides the feedback signal corresponding to travel of the valve.
6. The circuit of claim 1 , further comprising:
a sensor that provides the feedback signal corresponding to flow properties of material through the valve.
7. The circuit of claim 1 , wherein the processor is operative to,
compare the feedback signal to a threshold criteria; and
change the level in response to a relationship between the feedback signal and the threshold criteria.
8. The circuit of claim 1 , wherein the switch operates in the second state in response to failure of the processor.
9. The circuit of claim 1 , wherein the second state decouples the processor from the current-to-pressure converter.
10. The circuit of claim 1 , wherein the processor may be removed from the circuit with the switch in the second state.