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Re: Boiler priming and carry over

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Posted by Vern on May 29, 2004 at 23:07:39:

In Reply to: Boiler priming and carry over posted by Ken on May 28, 2004 at 12:36:47:

: At christmas time we opened all of our boilers for annual inspection. everything was great. We closed the boilers and started up on monday. We had trouble getting water into the boiler at one plant. After much inspection, it was determined,(by the carryover in the system) that it wasn't a feedwater problem, but a priming problem. This happened to a 600HP Superior Seminol firetube boiler which is fired at full rate most of the time. We also have a 500HP Superior Seminol boiler that is at a different location in the same town. When this Boiler was fired at a high rate, it did the same thing. We removed all of the chemicals, and started with a new source and one at a time. It will go fine for weeks and then upset. We have went through all of the water sofner valves and thought this might have the problem solved. Well, not so. I have checked all that I know. My TDS reading is below 1500. One question is can a small amount of water sofneer brine upset this boiler that bad and not have any effect on my TDS in the boiler. When the upset happens, my boiler shuts down on low water and when the TDS's are checked, they are just fine. I have zero condensate return. I have called the manufacture of the boiler and the DA tank and everyone else that I know and some that I don't know. Thanks

Excerpt from the Association of Water Technology training manual: There are seven reasons for mechanical carryover and only one of them can be corrected by chemical means. 1. Improper boiler design. 2. Improper maintenance 3. High water level in boiler or steam drum 4.Exceeding operational limits 5. Extreme or sudden load surges 6.Uneven firing 7.Improper water composition.

Excerpt: Priming is a form of mechanical carryover. This is caused by gross surges of water in the steam drum that literally throws water into the steam space, where it can be carried into the steam header. This can be caused by either improper design or improper operation. It sometimes can be corrected by changing the firing pattern, correcting false level indicators, or installing vertex breakers.

I don't think the small amount of brine you mentioned will cause the large carryover you are experiencing. Take chloride tests of the boiler water and compare the results with previous results to determine if you are getting brine to the boiler. Check to see if your boiler is overfull at startup. The boiler can pull a vacuum after it cools and suck process water back to the boiler. Possibly that could cause carryover. Good luck.

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