#LinkedInsights covers topics people discuss on social media platforms that relate to the Process Automation industry. Our feature today centers on the issues that an Instrumentation Engineer faces with a Differential Pressure Level Transmitter. Read on to find out more…  

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The Problem

An instrumentation engineer from ONGC Petro Initiatives Ltd, India, has been having problems with a DP Level Transmitter.

His problems have to do with service hydrocarbons: Specifically, two numbers of LT are at the same position on the same tank and provide heat tracing to LP through side impulse tubing. However, one LT is not working. Meanwhile, the other one is working perfectly fine. Lastly, the non-functional one has to flush from the LP side, where condensation observation takes place every 1-2 hr.

Image for DP type Level Transmitter
Image courtesy of emerson


Addressing such concerns, an Instrumentation and Control Engineer from Vietnam suggests swapping the good LT for the bad one. Also, he suggests constantly monitoring the problem through LT or steam checking.

However, an Instrumentation and Control Engineer from Seuz Steel Company, Egypt, recommends changes to the wet leg. Namely, he suggests filling the LP side with water and re-calculating the zero and span. As such, “if you use a heat tracer to prevent condensation, the wet leg impulse will cancel the heat tracing. Or, you can use a capillary tube,” he adds.

As a matter of fact, adjusting ranges is pivotal here. Regarding this, an Industrial Electrician Instrument Technician from South Carolina offers some advice. Specifically, he says that unless you keep the low side filled with condensation and compensate, you must use a dual capillary style transmitter. Also, you must adjust ranges for the said static head pressure.

Further, minimum maintenance and maximum accuracy have always been important for transmitters. Concerning this, a Site Instrumentation Technical Officer from Nyrstar, Tasmania, believes that since DP transmitters require higher maintenance and reflect measurement inaccuracy, a Dual Radar Level Transmitter could replace it.

Image for Radar Level Transmitter
Image courtesy of vega

Impulse Tubing

Addressing the specific issue of impulse tubing, an Instrumentation and Control Business Professional from WIKA Australia adds some insight. Concretely, he says, “If condensate is forming in the impulse line, you need to install a condensation pot. Then, fill the line with an isolating oil and re-range the transmitter to suppress the head of oil. Alternatives include using a remote seal or a remote sensor that works in a Master-Slave configuration.”

Furthermore, a senior sales representative from Emerson Automation Solutions, Los Angeles, discusses the pros and cons of a DP level transmitter. Namely, he believes that there are certainly many advantages and loopholes with DP level measurement. “One newer way to do this is with two gauge pressure units linked by HART to give you the differential digitally. In most cases, this can work. But speak with your local instrument vendor to see if it fits. Also, use an integral tank seal for each side. No wet legs or capillary unless extremely hot service in a tank,” he says.

Taking it ahead…

Continuing, a Sales Professional and Instrumentation Partner from India weighs in as well. He believes that, where the chances of condensation is a DP level transmitter, special instruments for condensation process applications can solve such issues.

Lastly, according to an E&I Engineer from Sapura Energy Berhard, Malaysia, “If everything is the same for both of the LTs, then condensation is caused due to a temperature difference. For the dysfunction of one of the LTs, it could be so that one transmitter might be installed at a hot place (maybe near some hot air outlet) and the other one in an open space.

To see the full discussion,click here.

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