What if you could extend the life expectancy of your fluid end block by 50% or more — while lowering your total cost of ownership? With Caterpillar’s innovative new fluid end geometry, introduced in June 2018 you can. Cat® Cube Bore well stimulation technology eliminates fatigue cracking to improve block life, yet it’s compatible with existing manufacturing tooling and fluid end components to keep your costs low. Here’s how it works:
Fluid end blocks are costly, and the design that’s served the well stimulation industry for years has reached its performance limits. That’s why we embarked on a project to develop new fluid end geometry. Before designing a solution, however, we set out to understand the issues with legacy-style fluid ends. After destructively analyzing many blocks and using cutting-edge technology to determine what was causing them to fail, one failure mode rose to the top: corrosion fatigue cracking at the intersection of the two bores.
Corrosion pitting in the presence of cyclic stress causes crack initiation on the material surface in contact with the high-pressure fluid. The continuation of stress cycling in a corrosive environment propagates this crack and eventually leads to block failure. Often the crack spreads across a sealing surface, resulting in high-pressure fluid eroding the block material. When that happens, the fluid end quickly loses its ability to seal, compromising the overall function of the pump.
Although there are a number of ways to overcome this failure mode, we found the most significant influence on product life to be stress concentration in the intersection of the two bores. In a cyclic stress environment, that concentration contributes to high alternating stresses, increasing the risk of fatigue cracking. Reducing the alternating stresses in the block requires modifying the geometry to eliminate the high-stress areas.
Once we identified the problem, our next step was to perform extensive stress analysis and correlate the results with field data findings. Then, we moved into idea generation, producing numerous geometric concepts — each one modeled, analyzed using finite element analysis and evaluated against each other and the legacy design. Through this process, one concept emerged as the clear frontrunner.
Cube bore geometry disperses stress from the high-pressure bore into the surrounding material. Legacy-style bore geometries focus this stress to the corners of the intersecting bore, resulting in high concentrated stresses in localized areas. Cat Cube Bore well stimulation technology removes material in critical areas near the bore intersections and smoothes large corners. That in turn smoothes the stress profiles and allows energy to be absorbed by the surrounding block material.
The result? According to validation testing performed in the field, the new Cat design completely eliminates the failure mode for intersecting bore corrosion fatigue cracking.
By reducing peak stress at concentration points by up to 40%, Cat Cube Bore well stimulation technology delivers an even greater increase in fluid end block life. Because the relationship of alternating stress to fatigue life is an exponential function, a 40% reduction in stress results in a 50% — or greater — increase in life expectancy for the block.
But that’s not the only benefit. Cat Cube Bore well stimulation technology also strikes the ideal balance between stress reduction and manufacturability. Its dimensions and tolerances work with standard machine tooling — allowing us to maintain manufacturing costs and eliminate the need for a substantial price increase.
Piece part compatibility is another advantage. The new design works with all current Cat® power end and fluid end components, so there’s no need to change how you operate or maintain your fluid ends — and you can retain your current parts inventory.
Bottom line, new Cat Cube Bore well stimulation technology combines innovative geometry with superior materials and proprietary material processing — all to help you achieve the next level of product durability and the lowest possible cost of ownership