Scott Newton, General Manager Mississippi Power Corporation, explains the problem at the Generating Station

by Scott Newton

On Monday of last week (June 11), we began an inspection at the generating  station, of our Unit #2, to investigate an issue we had been  experiencing. For some time, we have been unable to get full production  out of that unit (the other unit was fine). After performing virtually  every test/check we could think of, to find an electrical or programming cause, without determining the problem, we decided that the source must be within the turbine or penstock (9 foot diameter tube). Our  assumption was that there was something wrong with the turbine, so we  dismantled it on Monday (June 11). Everything seemed fine with the  turbine, but we had already planned (as part of bi-annual maintenance)  to have a certified turbine inspector examine it. He completed his test  on Wednesday (June 13). With the turbine in good condition, and obviously not the  source of the problem, we decided to inspect the penstock, to make sure  there were no obstructions in it, which could limit flow to the turbine.

On Wednesday afternoon (June 13) we entered the  penstock from the lower end (new Generating Station end) and walked up  toward the old station. As soon as we turned the first bend, heading  upstream, we noticed a large tear in the penstock. It was humped up in  the middle (up about 3.5 feet). From there it got higher and about 20  feet further up the penstock, it was bulged up in the middle so far that it was pushing up against itself (folded in half from the bottom up).  We were actually able to walk underneath the penstock, after crouching  through the tear, all the way up to the transition piece (which is where the penstock attaches to the old station. We estimate that the damaged  portion of the penstock is in excess of 200 feet in length.

Penstock as installed in 2009
Damaged Penstock as photographed this week

On Friday of last week (June 15), we entered from the upper end  (the old Generating Station). From that end, it appears to us, as though the  problem started at the seam between the draft tube (where the water  exited the old station) and the transition piece (which attaches the  penstock to the old draft tube). Inspections are underway to determine  the cause and solution. M. Sullivan & Son Ltd., the General  Contractor on the construction of the station, were here on Friday (June 15) of last week to inspect the damage. Our insurer sent  a representative today (June 20) to conduct their own  preliminary inspection. Genivar (the Engineering firm that designed the  station), will be here to inspect, later this week, or early next week.

In the interim, as a precautionary measure, we have shut down the unaffected unit  until it can be inspected by a qualified engineer. We did our own  inspection yesterday afternoon (June 19) and the penstock itself looks fine.  We do have some concerns about the condition of the weld in that seam,  but it  needs to be inspected by an expert. So, it will remain shut down until that can happen.