IR Model 29 APKD-6

Allen Pump received a contract to overhaul an IR 29 APKD-6 Heater Drain Pump for a 1100MW Unit.  The internal element removed from the pump well is driven by a 1,250HP motor, 1800RPM, 5,430GPM, 770TDH at 370F.  The component observations, corrective action plan and final documentation are included.  Click here for the full report.

Army Corps of Engineers were scheduled to run a typical functional test on their Worthington Hurricane Barrier Pumps.  The Pumps function is to protect the city of Providence when high seas surge.  In an event the gates are closed, and water is pumped out of this river bay.  When unit 5 was started The whole building Shook violently.  Once the shaking stopped and the pump appeared to settle out it was noticed that there was no flow output.  The blades had broken clean from the impeller and Charles G. Allen got a phone call.

Broken impeller blade prevented dewatering of suction pit

Gates are dropped in order to isolate the suction pit from the river bay.  2 Diesel pumps were brought in to dewater the pit.  After running all day, overnight, and half the next day it was determined that there was something causing water to enter the pit.  A diving team was commissioned to take a look.  A blade had broken off the rotating element and was lodged under the gate.  Cranes pulled the gates, the obstruction was removed, the gates dropped again and finally the suction pit was dewatered.

Broken impeller and suction bell

The Impeller was detached from the shaft, lowered out of the suction bell, rotated 90 degree’s and pulled out of the pit.  It was observed that all the blades had broken clear from the impeller.

Wooden patent created to make new casting

The propeller vane cracking is attributed to the type of material, Ni-Resist Type 1b.  Ni-Resist was used in the early 1960’s, but does not posses enough ductility therefore being brittle under stress. While in service over a long period of time, numerous micro-cracks in the original casting structure have greatly increased in size due to residual stresses, vibration, operating impacts, and other environmental stresses.

The original material is a contributing partner but poor design may take more of the blame.  There was a latent defect in the casting portion of the vanes. It is presumed that the problem is with the original hand sketch drawings of the early 1960’s before CAD was developed.

inside the pump

New Impeller

The 15,000 lbs, 119″ Impeller was delivered, balanced and attached to the 12″diameter 30′ long shaft.  It was aligned with the 4,500HP Electric Drive motor and spins at 150RPM.  The unit was restarted up in August, 2011 prior to Hurricane Irene, and was utilized during the storm surge.

Chas G. Allen received the call from the plant on Sunday to evaluate the 58,000GPM Johnston unit and found that the shaft had broken internally. As a turnkey service CGA provide field personnel to remove the equipment on a 24/7 basis. The unit was transported to our service center, disassembled and evaluated for a corrective action plan. The internal shaft coupling had a fracture and caused the unit to fail. A new coupling was manufacture and the pump was reinstalled at the site within 6 days.

The following is the time-lined inspection report. (full case study)

The station was in the 2nd week of a scheduled 4 week outage when during a routine cleaning of the intake pit it was discovered that the outer column had numerous holes 6” in diameter with serious erosion at the lower flange to the casing.  Chas G. Allen got an urgent phone call.

The 140,000GPM unit provides cooling water to a 650Mw base loaded coal fired station. This is a non-pullout style design in which the outer column was constructed in carbon steel and had deteriorated to near catastrophic failure in the saltwater. Several years prior the customer installed a carbon steel column from the OEM as the unit was schedule to be replaced within a few years of the last repair. Scheduling changes move the replacement project out another eight years from the original plan.

CGA evaluated the damage and devised a corrective action plan until a new column could be fabricated. Fabrication of the new column had minimum of 6- 8 week lead-time in 316SS. Due to the severe erosion and unknown actual thickness of the column, removing the unit would probably have due more damage to the other stainless components (shafting, inner columns, casing) and in-place repair was the only option.

Connecticut:

Coming out of a spring outage this pump read 40psi Discharge equating to approximately 840 GPM. In May the pump was observed outputting 10psi Discharge and guessed to be outputting 30gpm.  Gauges were replaced, numbers confirmed and Chas Allen Pump was answering the phone and scheduling a visit.

Allen sent our tractor trailer to the sight and hauled the pump back to Barre, MA. Mussels were power washed, and removed from the pump.

After disassembling & blasting; the Corrective Action Plan was as follows:

Shafts

Furnish the following five (5) new shafts in Pump Shaft Quality 316SS 1-Top shaft
2-Top Intermediate shafts 1-Lower Intermediate shaft 1-Pump shaft

Impellers

Excavate all cracks and dents on the inlet vanes Weld in accordance with proper procedures for 316SS
Hand dress weldments to original surface profile Assemble on the new pump shaft and dynamically balance, acceptance criteria 4W/N
Note: Due to the impellers are secured with collets, the impeller will be scribe for proper
location during reassembly

Suction Bell/Bowls/Transition

Remove the old cutless rubber bearings Furnish and install new bearings Polish the wearing surfaces for reuse Prepare for customer coating system by others
Columns/Spider
Remove the spider bearings Furnish and install three (3) new spider bearings and spider bearing brackets in 316SS Note: The spider bearing brackets long side faces the suction of the pump

Columns/Spider

Prepare by sandblasting for customer coating system by others

Discharge Head

Setup in VTL and skim cut minimal material from the soleplate mounting surface Sandblast to near white metal and apply two (2) coats of Belzona 5811 Immersion to
the exterior surfaces
Prepare the internal surfaces by sandblasting for customer coating system by others

Stuffing Box

Remove the old bearing Furnish and install a new bronze bearing Furnish and install new J-C 1065 packing 3 rings, lantern ring and 3 rings packing

Pump Delivered

The pump was delivered, and a second pump impacted with mussel’s 15′ away was removed and hauled to our site for a similar repair.