Project Overview

multiple_items_1123333194

This pump is used on a critical application on an offshore oil rig. It was taken out of service because it failed to hold pressure. Upon disassembly, severe cavitation pitting in the first stage side plates was found, as well as serious damage to the side plates between the first and second stages due to an earlier bearing failure, so that the side plates were in effect acting as a bearing. Wear to this area created a serious leakage path between the two pump stages.

The parts were measured using a CMM, modeled in CAD, and assembled. This allowed us to assemble the parts in space to generate an assembly cross-section and generate a Bill of Materials.

Working with the precise CMM measurements of both sizes and relationships between features in 3D space allowed us to detect wear and damage and to resurrect the original part dimensions so that correct assembly fits and pump running clearances could be applied.

At this point drawings were generated and industry-standard tolerances were applied to the critical dimensions.

A detailed scope of work was then generated, which enabled the project to be planned, which generated a quote and a delivery date.

multiple_items_1397859912

Our journeyman machinists and millwrights then performed the work such as in the photos below. Most of the work was done on our CNC machines, with QC checks of finished parts performed with the CMM. The CMM was used because it was able to measure GD&T such as parallelism, flatness, runout, and cylindricity, none of which can be measured properly using manual tools. The final as-built dimensions were used to adjust the CAD assembly model to track the actual finished product, which needed to hold a tolerance of .004″ over a stack-up of 22 critical dimensions over 2 pump stages.

The rotating assembly was dynamically balanced to better than G 2.5 as per ISO 1940/1. The permissible rotating imbalance was calculated and the readout from the balancing computer was included in the final report.

The final assembly was then performed by our most senior millwright.

After assembly and a final confirmation of as-built running clearances, the unit was pressure tested. The customer has since reported that the unit is installed running successfully.