Ductile Iron Pump Transforms Well Service Operations
Casting conversion delivers 20,000+ hour performance in extreme oil field conditions
When SPM Oil & Gas confronted persistent weld failures in their WS335 frac pump frames—critical equipment operating at 15,000 psi in 24/7 fracking operations—the conventional response would have been incremental weldment improvements. Instead, the company partnered with St. Marys Foundry to pursue a complete conversion to a casting. It wasn't easy, yet they ultimately achieved a 233% lifecycle extension.
Challenges
SPM faced chronic weld fatigue failures in 15,000-psi frac pump frames lasting only 6,000 hours, requiring a more durable, non-catastrophic alternative for continuous 24/7 remote operations in harsh, high-pressure field environments.
Solution
A casting redesign and multiple tooling refinements improved component geometries and manufacturability, as well as reduced lead time, casting defect rates, and post-processing labor.
Results
- 233% pump lifecycle extension
- 50% reduction in core box cleaning time
- 55% reduction in core assembly labor
- Zero production scrap
Unfiltered
"Early engagement and iterative tooling improvements enabled breakthrough results for this frac pump."
— Matt Pettus, Operations Manager, St. Marys Foundry
Award-Winning Casting Conversion
This casting conversion delivered a 233% lifecycle extension and 20,000+ hours of proven performance—earning the 2024 American Foundry Society Casting of the Year award while eliminating scrap, reducing manufacturing time, and redefining durability in extreme 15,000-psi frac operations.
Challenge
The original welded steel fabrication was prone to fatigue-related cracking after only 6,000 hours of service, with the nose plate area, which bore massive operational stresses, representing the primary failure point. The question posed by the foundry—"Why can't this be a casting?"—triggered a technical journey that would challenge assumptions about material selection, manufacturing feasibility, and overall design processes.
Initial discussions centered on gray iron, largely because the incumbent foundry supplier lacked ductile iron capability. St. Marys redirected the conversation toward ASTM A395 60-40-18 ductile iron, selected specifically for its superior yield and elongation properties that reduced the risk of catastrophic cracking—critical for equipment operating in remote, harsh environments. This material choice, though more challenging to manufacture, addressed the fundamental performance requirements rather than defaulting to manufacturing convenience.
Methodology
Over 80 MAGMASOFT® solidification simulations at St. Marys ran in parallel with continuous finite element analyses (FEA) at SPM, creating a feedback loop that refined casting geometry for both structural performance and manufacturability.
Weekly Zoom sessions between engineering teams addressed a fundamental challenge between machining and casting: machining-appropriate datums don't necessarily translate to effective casting datums. The shaft bore centerline, suitable for machining references, proved unsuitable for foundry dimensional control—a nuance that required design adaptation.
The customer's willingness to accept foundry feedback was instrumental. Rather than issuing rigid specifications, SPM adopted a "here's what we're trying to achieve" approach, enabling foundry engineers to propose geometry modifications that improved both castability and structural performance.
Sculpted high-stress areas received additional material and optimized curves—features difficult or impossible to achieve through fabrication—while cast-in internal lubrication passages eliminated the tangle of external hoses, fittings, and welded loop bars that complicated maintenance and created points of failure and leak points.
Manufacturing Evolution: Two-Generation Tooling Strategy
St. Marys adopted a pragmatic two-generation tooling approach. First-generation prototype-grade tooling enabled initial production and field validation over 1.5 years, revealing dimensional stability challenges in the original six-piece doweled core boxes.
Tooling Strategy
Core Box
Consolidated core boxes from six pieces to two pieces, each constructed of aluminum.
Core Production
Time reduced from 45 to 20 minutes while improving dimensional repeatability.
Core Assembly
Solution utilized ten cores—totaling 4,000–4,500 pounds per assembly—while maintaining stability and tolerances across production runs.
This iterative investment strategy delivered tangible results. Following the 2023 redesign, nearly 100 castings were produced with zero scrap while maintaining over 60-dimensional checks per casting. Cleaning time dropped 50%, from 14 hours to 7 hours per casting.
Results
Field performance exceeded projections. Pumps now consistently achieve 20,000+ hours of service life—with some units reaching 18,000–20,000 hours before scheduled rebuilds—compared to the 6,000-hour lifecycle of weldments.
The rigid cast frame extended the service life of internal components, including gears and bearings, thereby compounding the value of the conversion.
An unexpected consequence: wear and durability improvements reduced replacement demand, which led production to pause for 1.5 years as rental fleets and end-users shifted from disposal to reconditioning. Machine shops began stocking rebuilt units rather than processing new orders.
For SPM, the casting greatly improved their operations, and that is a win for all.
Transferable Lessons for Conversions
This conversion demonstrates that successful fabrication-to-casting transitions require more than technical capability—they demand collaborative mindset shifts.
Early foundry engagement at the concept stage, customer flexibility on design modifications for castability, and willingness to invest in iterative tooling improvements create the conditions for breakthrough results.
Material selection should prioritize application performance over manufacturing convenience, even when that choice increases technical difficulty.
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