Wind-Milling and Thrust Bearing Performance Analysis for Multi-Pump Nuclear Test Loop

National Lab Extends Contract with Hayward Tyler  for Equipment Supply and Engineering Services

Hayward Tyler, Inc. (HTI) designed, manufactured and supplied canned motor type primary coolant pumps for nuclear reactor (NR) flowing water test  loops at a US national laboratory. The loops  are designed to test reactor fuel and structural material for the NR program and support  the continuing need for irradiation test data.  Within the test loop, the coolant pumps are installed in series. When a newly determined operating scenario was identified in which the canned motor pump would wind-mill for extended periods of time (windmilling is when fluid is pumped through the non-energized canned motor pump), Hayward Tyler was asked to conduct an engineering study to determine if the as-built reverse thrust bearing was suitable for use during this scenario.

To evaluate the suitability of the bearing to operate under these conditions, two analyses were required: The first was a computational fluid dynamics (CFD) analysis to determine the rotational speed and axial load that the bearing would be subjected to under wind-milling conditions. The second was an analysis of the reverse thrust bearing to determine if it can maintain fluid film lubrication when operating at the speed and loading determined from the CFD analysis. Maintaining lubrication is required to prevent excessive wear and premature failure of the reverse thrust plate material. The CFD analysis was performed by Hayward Tyler’s design engineers. The bearing analysis was performed in conjunction with an external partner that specializes in bearing performance evaluations.

The results of the bearing analysis predict that the reverse thrust bearing will be able to operate under wind-milling conditions indefinitely without risk of damage or wear to the bearing. After completing the engineering analyses, HTI conducted a 30-hour performance test of a similar canned motor primary coolant pump under wind-milling conditions at Hayward Tyler’s Colchester, VT facility. The thrust bearing was examined post-test and showed no wear.