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Posted by DanD on March 14, 2008 at 02:35:19:
In Reply to: drum level shrink and swell posted by barnstable1197 on January 24, 2008 at 22:57:27:
:As many others have pointed out.. What if anything has changed recently? We use two element FW control, which means that besides looking at drum level alone, we also look at the steam flow from each boiler. If the steam flow goes up quickly, the FW controls will "Feed Forward" which is simply anticipating the coming hit to the drum level and adding water in advance. From time to time one of our boilers has the instrument taps, in the flanges for the Steam Flow orifice, plug up. We then get low level alarms and occasionaly LLCO's. I think three element looks at the FW flow also. Good Luck.
: I operate a large industrial coal fired boiler. In the past when we experienced large steam load swings the boiler drum level would go up or down a couple of inches off setpoint due to shrink and swell. Within minutes we would be back at setpoint. It seems now that with the same amount of steam load swings the drum level goes up or down as much as 7 inches off setpoint due to shrink and swell. The controls still manage to get back to setpoint in a timely fashion. My question is:What could cause the amount of shrink and swell to change on a boiler,if in fact it can change?