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Re: Drum Level Transmitter lines

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Posted by Steve on July 29, 2006 at 14:17:52:

In Reply to: Drum Level Transmitter lines posted by A BOILER-GUY on July 10, 2006 at 17:41:11:

: We now have Rosemount transmitters installed for drum level control on all of the boilers, boilers are all d frame water tube, running at 100psi. They seem to have a problem on the steam side when the boiler is on standby with the line plugging up. When in standby the boiler is just warmed every 8 hrs. to keep pressure on it for backup. Has anyone experienced this? If so do you have any advice on how to keep it from happening, it's only doing this when they are in standby 7 not when online. We were thinking maybe a blowdown line needs to be added at that point to clean it but don't know what effect this will have with the reading at the transmitter. Any advice would be helpful, thanks.

Boiler Dude,
Standard installation of a drum lvl Xmtr should have included blow down lines for the HP and LP legs of the Xmtr. If not, the Xmtr is not going to be of much use after a while due to plugging. I believe Rosemount should have supplied installation drawings with your purchased product, look for these to ensure that your installation is correct.

With the ability to "blow down" your Xmtr's you can do so as necessary to keep your HP and LP legs clear. The only real draw back is the time required for the legs to refill with water for proper operation. The LP leg(steam side) will require much more time than the HP(water side) because steam must condense to fill it. A fan to cool the lines will aid the recovery time.

To the meat of the issue, you have to ask your self why the lines are clogging in the first place. Boiler water quality is the key. Poor water quality can have many effects on the operation of your boiler. Not knowing the type of system you are running, ie: turbines or not or any other place that oil or grease can enter the system, its hard to tell from here what your clogging issue my be. At any rate, You know your system best, if you can see it in the drum gauge glass, its a fare bet its in your sencing lines for your Xmtr. Oils and greases have a nasty habit of clogging gauge lines and sencing lines due to their being cooler then the water drum only a few inches away. If there are other materials in the water that can act like the oils and greases, the same thing may be happening. Removing oil and the likes from your system is not always going to be easy and in some cases you can't at all. So the best you, as the operator can do is have a good routine of surface blowing your boiler on a very regular basis, not just opening the valve and let her rip, but a controlled blow that allows the water level to lower to the surface blow line as oil and her friend float well and can be removed from the surface. You will have to know where the surface blow line is in relation to the gauge glass as well as the mark at which your boiler will trip off. Surface blowing in this maner is not fun to say the least but is very effective in the removal of floating matter.

I am hoping I did not read your question wrong in that it seemed as though you were indicating that the steam leg was clogging up, that would be rare, and if it is the case, you have a whole new bag of worms to think about.

Hope I helped:)

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