During a 2021 freeze event in Texas, a major petrochemical refinery experienced the failure of several pump bearing housings throughout the facility.
Refinery case study reveals smart engineering solutions
A cracked cast iron bearing housing in a double ended pump.
The freeze caused major residential and commercial power outages across the state. When the refinery lost power, it also lost cooling water; cooling water which the bearings and bearing housings relied on to run at near optimum temperature. The cast iron bearing housings cracked from water freezing in the housing, resulting in the delay of the refinery's startup.
Some pumps were missing spare parts needed for startup, which could have resulted in significant economic penalties for the refinery. Furthermore, the failed bearing housings were castings, and the quoted delivery time was several weeks away . The proposed repair was to braze the bearing housings; brazing is a common repair for cast iron, which cannot be welded using traditional techniques. If the proposed repair did not work, waiting for a new casting would have added significant delays.
The objective
This event set in motion the mission to provide same-day, temporary repair service, while engineering long-term repair and preventative solutions. Conhagen's engineers would provide immediate response and restore operation to the refinery.
The solution
Cast iron cannot be welded, but it may be brazed. It is not an ideal repair because it is difficult to accomplish and has a high-repeat failure rate. In this case, it was used as a temporary repair to allow the refinery to be up and running and to avoid costly downtime. Concurrent with the braze repair, Conhagen engineers used contactless 3D scanning to digitize the bearing housing and reverse engineer all features and functions. This allowed Conhagen to improve on the current bearing housing design with minimal added delay to the repair.
Results
For the new bearing housings, Conhagen's engineers evaluated the existing designs and made recommended reliability upgrades. The upgrades fell into two categories -- style 1 and style 2.
New bearing housing style 1
Fabricated, water - cooled housing
The bearing housing was 3D-scanned prior to the temporary repair. Conhagen then fabricated a new carbon steel bearing housing. The advantage of carbon steel construction is the biggest benefit of style 1, which is now weld repairable. This repair would be considered permanent, as opposed to the braze repair, and allows for future weld repairs.
New bearing housing style 2
Air-cooled housing
Conhagen's engineers evaluated the bearing design and pump thrust calculations. They identified several of the frozen bearing housings that could be redesigned to eliminate the cooling water entirely. Based on the predicted heat generated, they were able to redesign the bearing housings, utilizing cooling fins which eliminated the need for water cooling. The new bearing design temperatures were still within the desired range for optimal bearing life. The new housings were machined from ASTM A276 Type 410 stainless steel and eliminated the failure mechanism entirely while still providing sufficient cooling to the bearing for reliable operation.
For more than 50 years, Conhagen has applied 'best in class' solutions to its products and applications and utilizes hard core rotating equipment design to develop unique results to specific client issues.
The company has an array of engineering services to suit your needs. Conhagen's engineers work directly with customers from root cause to implementing the best solution. If your company is experiencing cracked cast iron bearing housings, needs assistance with solving rotating equipment or has manufacturing needs, contact Conhagen.
For more information, visit conhagen.com or call (409) 938-4226.
