Few years back, when I newly joined my first Job, I was fortunate enough to spend a lot of time on Shop floor. Everything on the shop floor interested me a lot. Watching people assemble the multistage Pump was one of them. Later, in one of the projects assigned to me, I was asked by my Boss to solve the issue of increasing the Nozzle Loads for one of the type-series of Multistage pumps. It was a long pending issue, actually a request from Sales department, as most of the Customers asked for it and also Competitors were already upto it.

All the background work was also previously performed once, however, no fruitful conclusion was made as it was clearly seen from the report of FE Analysis that the deflection at the shaft end was beyond the Limits. So, I took this challenge and decided to dive deep into the matter. The problem was that, the colourful images, graphs, values and reports from FEA are so convincing that one might fail to see quiet obvious things.

The underlying problem was with the understanding of the Process. As I was new and spent lot of time especially looking at the Pump being assembled, one thing that always made me curious, is how one is Centering the Rotor and resting it properly on to the Journal Bearing Surfaces. So,my understanding of this process was very clear. Later, when I started studying the ANSYS report keenly, I noticed that, the Tightening torque to the Tie rods of the Pressure casings was applied independently, considering the Pump totally assembled with Bearing housings and that was causing the deflection of the Bearing housing and hence the Shaft end. However, while giving the Boundary condition, it was merely the lack of practical understanding of the Assembly process, wherein the Pressure casings will be tightened first and then the Centering of the Rotor will be done independently to transfer the whole rotor load on to the Journal Bearings. So after subtracting the effect of tightening torque the values dropped drastically within the limit. With this ,we concluded the issue before the deadline and then was happy and little nervous as well to give my first ever presentation of my work to our sales team.

So, FEA, Numerical calculations are the great tools to resolve such problems. However, correct understanding of practical processes is crucial.

(The image is only for illustration of API BB4 type pump with Journal bearing. Courtesy: https://www.pumpsandsystems.com/hot-pumps-thermal-expansion)