Steam sensing lines plugging

Question

Steam sensing lines plugging

FIG Journey (Mechanical)

(OP)

1 Jun 17 11:26

The client has differential pressure flow and pressure transmitters on a steam line that are plugging up with ammonium bicarbonate. The sensing lines are tubed to condensate pots then onto the transmitters. The condensate pots enable precipitation where the ammonia precipitates out of the gas phase as ammonium bicarbonate then plugs up the lines. Due to low budget and time they need to use the same style of measurement but redesign it to work. Their main idea is to remove the condensate pots, use root valves that take off below the process line, shorten the impulse lines and tube with a slop down to the transmitters then fill the impulse lines with Triethylene glycol that has a boiling point of 285°C.

Need your thoughts on this or any better way of doing it with the same measuring concept.

Thanks

hacksaw (Mechanical) · Answer 1 · 2017-06-01 17:17:50

you might consider use of continuous purging, though it carries it's own problems

FIG Journey (Mechanical) · Answer 2 · 2017-06-02 16:05:40

hacksaw, good idea but you are right in more problems. They don't need anymore maintenance problems then what they already have with the ammonium bicarbonate and are not willing to change the system or spend a ton for added features. We will just have to see how this present idea will work.

danw2 (Industrial) · Answer 3 · 2017-06-02 16:52:19

The issue I've heard of is that over time, condensate dilutes the fill fluid so the SG/density in the impulse lines change, resulting in a shifting zero/offset/DP.

waross (Electrical) · Answer 4 · 2017-06-10 04:42:40

I just saw in passing a type of level measurement without impulse lines.
At the low level a transmitter used a direct mounted pressure transducer.
A high mounted pressure transducer sent an electrical signal to the transmitter.
The transmitter compared the two pressure signals and outputted the difference.
Loop powered 4-20 ma.

Bill
--------------------
"Why not the best?"
Jimmy Carter

roydm (Industrial) · Answer 5 · 2017-06-13 16:06:10

You say the sensor is tubed to the condensate pots, why is that?
The condensate pots should be as close to the orifice plate as possible with 1/2 pipe connections that way they operate just below line temperature and the steam won't condense out so fast.

FIG Journey (Mechanical) · Answer 6 · 2017-06-14 11:36:53

waross: The pressure sensing element needs to be able to handle 300 degrees C plus temperatures. That is why they are tubed away from the process to cool down the process temp as there is not a sensing element that can handle such extreme heat.

roydm: The condensate pots are where the problem starts. When the steam condenses out so does ammonium bicarbonate which then plugs the lines. This seems to happening within the pots and that is why they are getting rid of them.

On top of it all these guys do not want to spend any money to upgrade their transmitters or change the way they are measuring it with another type of flow meter.

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Steam sensing lines plugging