Boiler Water Circulation Pump Steam Path Repair - Year Long Saga
Field System Machining was asked to provide machining, welding, and heat treating to repair a leaking boiler water circulation pump body. The pump was first believed to be leaking through the stud holes and rabbit fit--we welded the stud holes, bored them out, tapped them, and machined the gasket fit. Later in the year, it was believed that the rabbit fit was leaking, again; We machined it, again. A third time the pump began leaking and this time it was believed that cracks were forming all the way through the ligaments.
The utility power plant originally thought the indications of discontinuity developed from metal fatigue occurring over the circ pump's trusty fifty-three years of service. When, for the third time on-site machining excavation of the indications of discontinuity commenced, a surprise was in store for plant personnel.
An undocumented repair was made to the circ pump, involving cutting a large groove into the pump casing and shrinking in a stainless steel ring--this was discovered only after our repairing cracks in the bolt holes twice, passing metallurgy twice, only to have the cracks appear, each time again.
The turbine boiler water circ pump leak reappeared at an inconvenient time--while the 270 MW unit was operating at full base load, 24/7. The plant asked us to make a plug and weld it into place as quickly as possible so that the unit could be put back on line. That plug appears above.
Above you can see that hand excavation a.k.a. crack chasing has commenced on the boiler water circ pump casing. Note that excavation straight through the ligaments was necessary.
Above you can see that not only did we chase cracks, we also machined straight down the rabbit fit and inside the rabbit fit into the circ pump body--that is where the foreign material ring was located. It is unknown when and why the non-ferrous ring was shrink fit into the circ pump body.
This is the boring setup used to machine the rabbit fit and pump casing body. This is also how we machined out the temporary isolation plug.
Excavations are complete.
Heat treating preheat soak is complete and welding is about to start.
Welding up the massive excavations. I love the smell of weld fumes in the morning.
Weld repairs are completed.
Finish machining is under way. The red cage is one of dozens of boring cages FSM has manufactured.
Completed, like new, and ready to go back on line. Field System Machining has been solving power plant outage steam path repair needs since 1978. Field System Machining has performed over 1,000 projects for this one customer, alone.