Accumulated Water in Transmitter Tubes

if the process line is hot than you should install in a fashion condensate accumulates in the impulse tube,see that the impulse line is below the process line and if the condensate is corrosive in nature than the impulse line to be glycol/ glycerene filled so that the sensor of the transmitter is protected .

flushing the impulse line on this line will be hazardous as it may contain piosonous gases and may contain unburnt fuel may catch fire . see to the standard operating proceedure in the department for such type of instrument maintenance .

Maybe you need to put an isolator in between your process. Or find a good transmitter that can withstand the heat and have a routine for clearing out the lines, with air.

As the issue mentioned here is water condensate buildup from combustion in the impulse lines there is no reason to consider flushing, it is impractical since it would mean taking the transmitter out of service or still add to the accumulation of condensate in the impulse line.

Also heat affecting the transmitter is not an issue, the initial dead leg of gas trapped in the impulse line acts as an insulator so the hot process is not seen by the transmitter, this trapped leg will be present from start-up. This is further evidenced by the fact that there is condensate accumulation, if the temperatures within the burner were being seen at the transmitter the condensate would have boiled off.

Your best options are;

1. If the transmitter cannot be moved due to accessibility and to much extra works regarding new cabling etc. add the condensate pots with appropriate isolation valve so that they can be isolated and drained with out taking the transmitter out of service. (You should be able to obtain a suitable process hookup drawing/detail from the internet to give you some ideas).

2. Move the transmitter so that it is above the process connections.