Industrial Automation Insider‘s Andrew Bond wrote an article for ControlGlobal.com, DVCs Drive Digitization of the Process Industries. It describes the introduction of digital valve controllers by Emerson’s Fisher business in the 1990s and their widespread use–more than one million FIELDVUE instruments sold.
One thing caught my eye:
Over the years increasing capability has been built into the Fisher device. Indeed the diagnostic capabilities of the latest version, the FIELDVUE DVC6000 Series, are such that Emerson claims that plants can operate for five to seven years between maintenance shutdowns.
Emerson’s Danny Nelson was quoted in the article, so I asked if I could get more background on the 5-7 year statistic. Danny sent me a presentation by Ken Hall, whom you may recall from an earlier handheld device valve diagnostic post.
Manufacturers in many industries including refining, chemicals, and petrochemicals have extended their plant turnarounds (planned maintenance shutdown periods) from an annual event out to 5-7 years. Checking the performance of the control and shutdown valves is one of the key activities performed during these turnarounds.
Since the digital valve controllers have embedded diagnostics, the valves with these attached perform performance diagnostics on a continuous, non-intrusive basis. Their objective is to identify problems before they impact the process. Problem descriptions, possible causes, and recommended actions are provided back to the maintenance team through the asset management software.
Some of the conditions the diagnostics can uncover include supply pressure issues, I/P & relay integrity, travel deviation, and air mass flow for leak detection in actuators. Additional friction/dead band tests can help spot stem deformation, plug wear, packing issues, and trim damage.
Prior to these ongoing diagnostics, the valves would have to be pulled from service and looked over in the maintenance shop. Now they can be repaired proactively as the diagnostics report problems. This is one reason that plant turnaround lengths can be extended out to 5-7 years.
