Repair & Maintenance Of Pumps

Repairs and Maintenance of Pumps

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Maintenance and Repair of Pumps • The following slides are a summary of several categories of pumps used at the Allegheny Energy Power Stations: • Turbine Driven Boiler Feed Pumps • Motor Driven Engineered Pumps • Large Circulating Water Pumps

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Turbine Driven Boiler Feed Pumps •

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Allegheny Energy’s Power Stations with turbine driven boiler feed pumps are designed so that we have two 60% capacity pumps for each unit and we have a spare removable element that is interchangeable with each pump at any particular station. The interchangeable element is swapped out during planned outages based on the evaluation of our predictive maintenance data or during a forced outage in case of pump problems. Allegheny Energy uses two suppliers for the inspection and repair of our spare turbine driven boiler feed pump removable elements. One is Siemens Demag Delaval, the OEM for most of our turbine driven pumps, and Hydroaire Services, Inc., a high quality nonOEM pump repair shop in Chicago, IL.

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Turbine Driven Boiler Feed Pumps • Once an element has been inspected by one of the two approved vendors and a repair work scope identified, Allegheny develops a repair specification and bids the repair to both approved vendors. • When the bids are received, they are evaluated for technical compliance to the specification with adjustments made as necessary to ensure that the bids are comparable. • Then the Procurement Department determines a low evaluated bidder and issues a purchase order to cover the repair. • Engineers from the corporate Technical Services Department visit the vendor shop and monitor the repair for adherence to the specification.

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Turbine Driven Boiler Feed Pumps • One recent issue that Allegheny Energy is dealing with on our Delaval BFP’s is the catastrophic failure of impellers. The next couple of slides show a cross-section of one of our pumps and a picture of a failed impeller. • The failed impellers are believed to be the result of pressure pulsations from recirculation that occurs during low flow operation. • To resolve this problem Allegheny is making operational changes to minimize the low flow operation of the pumps. Changes include not hydrostatically testing the boilers using the BFP’s to pressurize and increasing the minimum load that the units will be operated at with two BFP’s in service.

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Turbine Driven Boiler Feed Pumps

• Additionally, Allegheny is going to implement the “A” and “B” gap modifications developed by Dr. Makay and EPRI.

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Turbine Driven Boiler Feed Pumps

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Turbine Driven Boiler Feed Pumps

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“A” Gap Modification

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Turbine Driven Boiler Feed Pumps • During typical inspections of boiler feed pumps and BFP turbines, Allegheny has been finding and repairing several major items. • On the feed pumps, Allegheny has been finding cracked impellers and worn wear components such as wear rings and seal sleeves. • On the BFP turbines, the major issues have been erosion of the diaphragm slots in the casings where the stationary diaphragms fit and cracked seal welds on the inlet valve seats. The diaphragm slots have had stainless steel liners installed which were then remachined to re-establish the correct axial location for the diaphragms. The seal welds on the inlet valves have been machined completely out and rewelded using automatic welders.

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Turbine Driven Boiler Feed Pumps •

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Allegheny inspects the BFP turbines on approximately 9 year intervals based on predictive maintenance and performance data. Allegheny’s BFP turbines have been very reliable with very few forced outages as have the feed pumps themselves, except for several impeller failures which are being addressed. One recent modification that has been performed on the BFP turbines is the replacement of the original mechanical speed control devices with electronic speed controls. These electronic speed controllers have allowed Allegheny to eliminate the need to actually run the BFP turbines to overspeed for testing. With the electronic controls, the trip set point can be changed to approximately same as normal running speed. The turbine can then be verified to trip without having to disconnect the pump. This saves many hours of down time during the startup of units following major outages.

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Motor Driven Engineered Pumps • Allegheny Energy’s Power Stations with motor driven engineered pumps are typically set up with either two 100% capacity pumps or three 50% capacity pumps per unit. • This category of pumps includes boiler feed pumps at our smaller stations, condensate pumps throughout the system, and circulating water pumps at our smaller stations. • The maintenance intervals on these pumps is determined by both predictive maintenance data and service hours. • Allegheny uses primarily three vendors for the inspection and repair of these pumps. The vendors are Flowserve in Cleveland, OH, Cleveland Pump Repair in Twinsburg, OH, and Daman Industrial Service in East Brady, PA.

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Motor Driven Engineered Pumps •

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For this category of pumps, the entire pump is shipped to the vendor for inspection and repair. Once the pump has been inspected by one of the three vendors and a repair work scope has been identified. Allegheny develops a repair specification and bids the repair to the three approved vendors. When the bids are received, they are evaluated for technical acceptance with adjustments made as necessary to ensure that the bids are evaluated fairly. Then the Procurement Department determines a low evaluated bidder and issues a purchase order to cover the repair cost. Engineers from the corporate Technical Services Department visit the vendor shop to monitor the repair.

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Large Circulating Water Pumps • The large Allegheny Power Stations have two 50% circulating water pumps per unit. • These pumps are very large with flow rates of 125,000 GPM to 150,000 GPM and weights of 75,000 lb. to 100,000 lb. Therefore, it is not practical to send these pumps off site for inspection and repair. Only the impeller and rotor shaft are sent out for inspection and repair. • The process for the impellers and rotors is the same as that used for the motor driven engineered pumps. The pump casing and stationary components are inspected and repaired on site by station personnel or contractor craft labor.

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Large Circulating Water Pumps • In November 2006, the 32 circulating water pump cast iron casing at our Hatfield’s Ferry Power Station failed catastrophically. This pump is a 1960’s vintage Foster Wheeler DS54 rated at 125,000 GPM. • The lead time for a replacement cast steel casing was in the nine to twelve month range, which would have meant that Allegheny would be at risk of significant derates at Hatfield during the summer of 2007. • Based on some R&D work that Flowserve had performed in the 1970’s when they were Ingersol Rand, they proposed fabricating the casing with steel plate. To the best of our knowledge, this new casing is the largest fabricated split case horizontal double suction casing ever built.

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Large Circulating Water Pumps

• An order was placed for the new pump on January 26, 2007, and the pump was delivered to Hatfield’s Ferry Power Station on June 1, 2007. • The pump was installed by June 7 and is currently in service.

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Hatfield 32 Original Circulating Water Pump

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Hatfield 32 Failed Circulating Water Pump

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Hatfield 32 New Circulating Water Pump

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Summary • The previous slides have explained Allegheny Energy’s maintenance and repair practices for three classifications of pumps: • Turbine Driven Boiler Feed Pumps • Motor Driven Engineered Pumps • Large Circulating Water Pumps

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