Day in, day out, and night after night, activity at a fracking site goes on without ceasing. Sitting at the surface of a miles-deep wellbore, a nearly 3.5-ton pump runs 24 x 7, pressurizing fluid at 15,000 psi to crack rock deep in the earth and release oil and gas. It’s brutally wearing work and the life of the pump is generally spent after 6,000 hours, at which time it is discarded. 

But that was when the pump was fabricated as a weldment. Today, there’s a new pump in town, and this ductile iron casting made by AFS Corporate Member St. Marys Foundry for SPM Oil & Gas, a Caterpillar company, is outperforming its predecessor with many more times the working life in the field. This patented cast frame for the SPM WS335 frac pump has also captured the 2024 AFS Casting of the Year Award. 
The frac pump frame, manufactured with the gravity pour/nobake sand casting method, measures 67.4” x 53.4” x 43.6” and weighs 6,600 lbs., a typical-size casting produced at St. Marys. However, typical in all other respects it is not. 

“This is a very difficult casting and it’s very difficult to make the cores,” said Brian Anderson, St. Marys’ production manager who’s been with the foundry for nearly 50 years. “Our team really stepped up and consistently made good cores and castings that were as close to identical as you can get with a casting that size––and with very little scrap.”

In fact, following a redesign a year after the original deliveries, the foundry produced almost 100 castings with zero scrap. 

But how strong is this casting? (1) Think tough––as in Ductile ASTM A395 60-40-18, which provides high strength in freezing temperatures of the North, as well as elongation that will slowly reveal if a failure is occurring versus a catastrophic crack. (2) Then think tougher. Strength was multiplied by virtue of becoming a casting versus a welded unit, but deeply collaborative and innovative design between SPM and the foundry yielded a Rocky-like pump that refuses to flinch under daily beatings.  

According to SPM, the pumps are operated in very harsh conditions––customers are asking a lot more out of this equipment from a power density perspective than is really seen anywhere else. It’s also the piece of the system that sees the first operational failure if there is a pressure spike happening underground—it will hit the pump first before anything else, so it’s got to be able to take some abuse.

SPM had been focused on resolving fatigue-related cracks occurring in the field, which had limited the life of the welded version of the product. The chief problem area was the nose plate at the front of the pump, which is subjected to massive stresses. 

With the casting, they started looking at how they could adjust the geometry and bring more material into that location––soon, they were able to clear some of those hurdles and have since ceased having failures in those locations.

The casting has, in fact, removed all worries about stress-points in general. 

According to SPM, they took a frame that everybody had said couldn’t be done in a casting, eliminated all the welds, and sculpted high stress areas to be exactly what they needed them to be. The company noted that this is hard to do with a fabrication – adding a curve in or extra mass into an area can really only be done with a casting.

Simulation + Conversation

The conversations with St. Marys started in the summer of 2019 with Black Horse, a joint venture between Caterpillar and Ariel Corp. to build fracking pumps. When Cat acquired Weir Oil & Gas to launch SPM Oil & Gas early in 2021, the move toward casting the pump frame was welcome news to the SPM team, where conversion to castings was already a favored idea. Early meetings covered the scope of the part and the foundry’s feedback on castability and tooling. Soon, weekly and bi-weekly Zoom calls between SPM and St Marys engineers dealt with ongoing design changes supported by over 80 Magmasoft simulations at the foundry and continuous finite element analyses at SPM.

“We kept feeding that data back and forth, saying we need to add material here for stresses or maybe draft it a little differently to make it easier to tool up,” said Karl Warsinski, metallurgical engineer at St. Marys. “So, there were months of back and forth on a regular basis.”

According to SPM, once the initial development was done, intense collaboration followed between the foundry and the customer’s engineering team, which included Daryl Belshan, who is named on the patent. Embarking on a complicated casting that hadn’t been done before, the company emphasized that tight communication among the right individuals was just as important as having the technical pieces and technologies in place, such as solidification modeling.  

SPM says its collaborative mindset resulted in the breakthrough durability the casting has since achieved in the market.

The customer leaned on the foundry to control more variables that aren’t typically put under as much scrutiny. For example, the SPM team was very concerned about weight and couldn’t allow much extra material, draft and other things that often occur with a casting. New challenges arose on almost a daily basis that kept both groups solving the question of how to fix one problem while still achieving the material properties they wanted or acquiring a necessary feature.

In situations like this, SPM stated it finds the most value by having open collaborations with its critical suppliers, such as St. Marys, and bringing them into the design process. Rather than saying, “Here’s the drawing, here’s the spec, go make it,” SPM takes the approach of, “Here’s the proposed drawing, here’s what we’re trying to do.” Understandably, they were flexible on some things, but elsewhere some pieces had to be right on the money. Because the customer took a more open approach, they saw many suggestions from St. Marys about geometries and other issues in the casting.

Muscling Through Challenges

Initially, the core boxes St. Marys outsourced were posing problems with dimensional stability, according to Matt Pettus, the foundry’s quality manager. Made of wood and urethane, each core box was split into six pieces. The team redesigned and rebuilt new ones with aluminum, and by giving each box just two splits, they were able to gain significantly better dimensional repeatability from casting to casting, he said. 

On top of building the core boxes, making and assembling the cores within their tolerances was one of the project’s biggest challenges, according to Anderson. 

“We would assemble 10 different cores together and set it all as one unit,” he said. “The unit weight was between 4,000 and 4,500 lbs., set into the mold at once––and it was really tough keeping 10 different pieces stable for every single casting.”

Warsinski recalled another obstacle in need of resolution: “On the design side, the functional geometry they need has a lot of isolated sections,” he said. “So we had to work on where we could add feeding paths to make sure we had sound iron everywhere they needed it. When you have a heavy section isolated in the middle of lots of cores, it’s hard to get risering positioned to feed to it. So we did have some design challenges there, where we had to add features just for castability. It can create a tension between what’s easier for a machinist to work on versus getting sound iron everywhere.”

Volume was also challenging. The customer’s demand expectation was 10–12 per week, but at first the foundry could turn out one or two in that timeframe. Eventually they brought their rate up to three or four, constrained in their capacity by other production commitments. 

The casting’s redesign in 2023 (sparked by the need to replace worn pattern equipment) solved a number of issues, made the part easier to cast and machine, and also enabled SPM to add some additional features, said Pettus. The new design also shaved off 50% of the time spent cleaning the casting––from 14 hours to about seven. 

No amount of engineering or workarounds could remove one required aspect of the job, which was a considerable amount of certifying, validating, and testing, all accompanied by digital reams of administrative paperwork. More than the usual levels of x-ray as well as non-destructive and destructive testing were called for to ensure the absence of shrinkage and internal porosity. Pattern Manager John Wendel said the foundry had over 60 different dimensions to be checked on every casting.

Customer Response

Attention to all the details paid off. The SPM WS335 frac pump has taken the 6,000-hour lifecycle of the previous weldment to 20,000 hours and higher. And customers in the oil and gas industry are loving it. In fact, the gains in performance have triggered a transformation among end-users in how they’re deploying the equipment, according to SPM.

Today, instead of throwing away the whole pump when it reaches the end of its operational life, customers are taking more of a rebuild and remanufacturing view to their equipment, according to SPM, getting two, three, and four additional lifecycles out of the frames. So, SPM works more than ever with its customers to provide remanufacturing service, adding sleeves or welding up worn areas. Bottom line, the durability of the casting has changed customer mindset, and they don’t have to buy a new pump at their previous frequency. Instead of ordering a new product, they’re simply dropping off their pumps at an SPM service center.

The long-lasting, rigid cast frame––serving as the central supporting hub of the pump––has produced the additional benefit of extending the operational life of other internal components such as gears and bearings.

In its reincarnation as a casting, the pump frame has acquired a new and special built-in feature that is also winning the appreciation of SPM’s end-users. Previously, the pump was encumbered with numerous hoses, fittings, and welded loop bars to facilitate the routing of lubricants throughout the frame. This complicated maintenance for customers over the life of the unit. Getting lubrication where it was needed was challenging, and failure in a lube system could destroy expensive equipment; in addition, leaks and burst hoses were not uncommon. 

Once again, the SPM and St. Marys teams successfully collaborated to cast in many of the internal passages, largely eliminating the add-on of hoses and fittings in the pump, according to SPM. And that, as the company notes, is driving high levels of quality, performance, and peace of mind for end users.

Part of the lubrication infrastructure depends on a machined feature, but even this is enabled by the design feats of the frame casting. A 5-ft. gun-drilled passage would only be feasible, said the managing director of St. Marys Foundry, Angela Schmeisser, if the casting was of highest quality iron––which it is, she affirmed.  

“We are so proud of the whole St. Marys team and how they truly exceeded the expectations of our customer,” she added. 
Their in-house achievements included designing the tooling, cores, and molds, then pouring the castings––over 250 to date––heat treating, cleaning, and outsourcing painting; then conducting structural testing, dimensional checks, and visual documentation of every casting delivered to SPM. 

“On some of our recent calls with our customer, they sound pretty excited when they’re telling us they’ve got 18,000 or 20,000 hours on a frame,” said Pettus. “It’s a great feeling to know that what we made is holding up in a harsh, destructive environment where the previous frames would break after a short period of time. We have highly-skilled, dedicated people working on this casting, and it’s exciting for all of us to hear how well it’s performing. 

According to SPM, the company is not only excited but proud.
The customer buzz the company hears sounds like: “Hey, this is really great––where else can we use this technology in our operations?” Listening to their customers and then working hard to deliver something they want more of––that’s the validation SPM’s team is always looking for. And as the company eyes more ways to incorporate castings into its products, more praise––and purchases––are sure to follow.  

Click here to view this article in Modern Casting.