Collaborative problem solving occurs in all kinds of ways—face-to-face, over the phone, via email, and online in blogs, on-line communities, wikis, and social networks.I mention this because I saw some great guidance on flow meter coating challenges in refining applications from Emerson’s Tom O’Banion. It was posted on an internal Emerson knowledge sharing site, but I thought it was well suited for anyone with these challenges.
Tom’s thoughts apply to any fluid that tends to coat or plug due to fluid velocity or temperature challenges. If the meter is coating either due to fines or temperature, then other components in the piping system will be too.
It’s quite rare that the flowmeter is the only “symptom”. It however can be the item that is the more difficult to clean or “melt out” due to tube geometry, or the difficulty in getting the solidified material re-melted.
With asphalt applications such as loading, paving machines, etc., Tom and Emerson refining industry consultants usually suggest that the meter has its own heat-tracing circuit and controller. With electrical heating, it’s easy to overheat the meter, especially is not a high-temperature version, and damage coils, magnets or RTDs.
It is best to leave this heating ON all the time, and have an insulating jacket—regardless of whether the application is intermittent or not. The cross-sectional area of the meter tubes is indeed usually smaller than the piping, so velocity is usually higher but may not be high enough—due to pressure change (delta P) concerns during sizing—to keep the meter swept clean. This is especially true of gravity-fed applications where pressure is minimal.
Refineries with “goopy” applications often flush the entire piping loop with solvent at some scheduled interval. Some refinery operations personnel monitor the meter’s drive gain (metric of how hard the meter is working) and use that to trigger the cleaning cycle.The Micro Motion 5700 transmitter has an embedded historian that can be set up to track these conditions in order to provide “forensic data” that may be able to explain what happened in the days or weeks prior to the perceived trouble. This can be a very helpful resource in troubleshooting the piping system and not just the flowmeter.