System and method to monitor characteristics of an operating fluid in a process line

1. A valve assembly comprising:

a valve with a closure member that moves relative to a seat;

a pneumatic actuator coupled with the closure member on the valve;

a valve positioner coupled with the pneumatic actuator; and

a device adapted to measure particulates in instrument gas supplied to the pneumatic actuator, the device having a flow pathway, the flow pathway having an inlet to couple with an instrument gas supply line and an outlet exhausts to environment,

wherein the device resides in the valve positioner, and

wherein the device is configured to divert a sample of the instrument gas from the flow pathway proximate a sensor to identify contamination therein.

2. The valve assembly of claim 1 , wherein the sensor comprises a light source and a detector that is sensitive to light from the light source.

3. The valve assembly of claim 1 , wherein the device comprises:

a chamber spaced apart from the flow pathway, and

a sample line coupling the flow pathway to divert the sample into the chamber,

wherein the sensor is responsive to the instrument gas in the chamber.

4. A method of operating a process line, said method comprising:

flowing instrument gas through a valve positioner to a pneumatic actuator on a valve assembly;

receiving data from a sensor disposed inside of the valve positioner, the data corresponding with contamination of a sample of instrument gas flowing past the sensor;

aggregating the data to illustrate a change in contamination of the instrument gas over a period of time;

using the change in contamination to predict a time frame during which the valve assembly might fail; and

generating an indicator that causes a pre-emptive action to occur at the valve assembly, wherein the pre-emptive action corresponds with maintenance within the time frame and before the valve assembly manifests problems that are detrimental to the process line.

5. The method of claim 4 , wherein the data reflects contamination of instrument gas on-board the valve assembly.

6. The method of claim 4 , wherein the data reflects contamination of the instrument gas at a location on a supply line upstream and within two feet of a connection with the valve assembly.

7. The method of claim 4 , wherein the data reflects contamination of instrument gas from a first stream separated from an instrument gas supply line.

8. The method of claim 4 , further comprising:

forming a first stream of the instrument gas from an instrument gas supply line;

forming a second stream from the first stream, wherein the data reflects contamination of instrument gas in the second stream that is separated from the first stream.

9. The method of claim 4 , further comprising:

comparing the aggregated data to a threshold criteria, wherein the indicator reflects that the aggregated data deviates from the threshold criteria.

10. The method of claim 9 , wherein the threshold criteria defines a level of contamination that is known to cause problems on the valve assembly.

11. A method of operating a valve assembly, said method comprising:

receiving an incoming supply of instrument gas into a pneumatic actuator coupled to a valve positioner secured to the valve assembly;

directing a first sample from the incoming supply of instrument gas;

forming a separate, second sample from the first sample;

flowing the second sample proximate a sensor inside of the valve positioner; and

using an output from the sensor, measuring a characteristic of the second sample that identifies contamination present in the instrument gas that enters the valve assembly.

12. The method of claim 11 , further comprising:

exhausting the first sample to environment.

13. The method of claim 11 , further comprising:

generating an alert in response to a value for the characteristic of the second sample that deviates from a threshold value.

14. The method of claim 11 , further comprising:

drawing the first sample from a supply line at a location proximate the valve assembly.

15. The method of claim 14 , wherein the location is within two feet or less of the valve assembly.

16. The method of claim 11 , further comprising:

drawing the first sample from inside a valve positioner found on the valve assembly.

17. The method of claim 11 , further comprising:

generating a beam of light at the sensor that penetrates the second sample, wherein the output corresponds to breaks in the beam due to particulates in the second sample.