Tips for better pressure, temperature, flow

By Control Engineering Staff January 19, 2006

Proper application of sensing elements can improve efficiencies and reduce costs, according to a Emerson Global Users Exchange session offering advice on selecting, applying, and maintaining pressure, temperature, and flow sensors.

Suggested best practices include the following.

  • In capital expenditures look at how to reduce overall instrumentation capital costs, then how to realize savings once instrumentation is installed. Look at critical versus noncritical instrumentation, monitoring applications, and single-point and high-density points, critical controls and safety—be aware of application requirements and the portfolio of products available.

  • Multi-input temperature transmitters can reduce installation costs, reducing wiring.

  • With differential pressure level applications, using a packaged system can save 20% overall in labor with easier mounting and in reduced materials.

  • In-line direct-mount orifice or vortex flowmeters can save more than a thousand dollars in labor, engineering, and materials, compared to a traditional orifice meter.

  • More accurate measurements allow moving the setpoint closer to actual process requirements, which reduces scrap, increases throughput, adds quality, and reduces energy costs.

  • With temperature measurement, the biggest source of error is the sensor. Using sensor matching an application can realize 50-75% accuracy improvement through tighter sensor calibration.

  • Use tuned seal systems to improve differential pressure level performance and reduce costs. Tuned systems have performance that’s pre-validated, with minimized temperature effects and better time response. Performance can improve by 10-15%.

  • With clean-in-place systems, continuous monitoring can reduce cycle times by 10-20%, reduce lab costs and automate temperature verification, reducing contamination risk, while consistently verifying sterilization.

  • Smart transmitters and selecting the right transmitter / sensor system for the application help to extend time between calibration, reducing maintenance costs.

  • Use diagnostics. Alerts can be set to help diagnose and troubleshoot problems, such as sensor drift alert, hot backup, statistical process monitoring, plugged lines, grounding/wiring, and process parameters (pressure, temperature, and flow).

  • With technical calls for magnetic flowmeters, grounding and wiring challenges are most common; calibration is next. If grounding is a problem, there’s a jump in signal amplitude at certain points (60 Hz) in magmeter coil frequency. Software can signal the fault and provide advice on fixing the issue in one try.

  • Give some thought about what sensor will be used in an application. Look at sensor construction and specifications; choosing the right one can improve performance. When measuring temperature, sensing elements are often forgotten.

  • With pressure, particularly in food and beverage applications, paying attention to the size of the diaphragm seal or process interface can offer operating advantages and gain real estate.

Emerson Process Management’s Brad Budde, senior marketing Rosemont, focus life science and food and beverage, and Scott Johansen, marketing engineer, temperature sensors division, provided the knowledge above. The meeting was held in October, 2005, in Orlando, FL.

For related news from Control Engineering , see:

  • “ Smart Remote Automation extends Emerson’s PlantWeb ”

  • “ Instrumentation leadership tips from Lyondell Chemical ”

Mark T. Hoske , Control Engineering