Emerson Exchange 365

A question recently came through from a refiner studying the revamp of an Asphalt plant, which will involve several pressure tansmitters. The customer is concerned about the characteristics of this process, with high temperature, high viscosity liquids. Having in mind that viscosity will increase during periods between batches, due to lower temperatures, the customer was interested in knowing how other refineries manage to prevent problems in such occasions.  The following recommendation came from my experience with refinery Coker units.   If you have any other recommendations please share.

1) fill the sensing lines with glycol or glycerin. This is recommend on any heavy oil service to keep the product from getting to the transmitters or into the sensing lines. 2) Heat (steam or electric) trace the process connections. This keeps the product hot and avoids it plugging the take off.  Make sure the transmitter is not heat traced. 3) Make the process connection as large as possible 1-2" is ideal, but not always possible. 4) Install a continuous flushing system using a lighter oil (cycle oil, diesel, etc.). This method can work very well but can also be hard to maintain if operators and instrument technicians are not familiar with it. 5) Install the transmitter as close to the process as possible. Especially if the sensing lines are not heat traced.