Given the intense conditions that well stimulation fluid ends endure hour after hour, it’s impossible to stop fatigue, cracking and eventual failure. What is possible is designing fluid ends to withstand more fatigue, so they crack later in life and resist failure longer—preventing downtime and saving you money. That’s what Cat® Extreme Duty (XD) Stainless Steel fluid ends deliver.
We can’t alter the environment inside a fluid end, where continuous changes in fluid pressure and cyclic stresses encourage fatigue. Instead, we altered the geometry to lower those stresses significantly. Here’s how:
In our previous design, five bores sat side by side. The three inner bores had no problem resisting fatigue, because they gained additional strength from the bores on either side. The two outer bores, however, were more susceptible to cyclic loading.
Cat XD Stainless Steel fluid ends feature additional material on the two outer bores so they’re supported just like the inner bores. That allows for a higher autofrettage pressure and therefore a higher residual stress level inside the intersecting bore—a highly effective means of adding longevity to the fluid end in a cyclic loading environment.
Groove-less valve retention is standard on all Cat XD Stainless Steel fluid ends, and it’s another fatigue-fighter. While grooved designs do their job of keeping the valve in place, retaining grooves in a fluid end can create two huge stress risers in the process. Our groove-less valve stop design does away with this commonly used industry design flaw, a major initiator of cracks.
Historically, a larger plunger size required a larger valve to accommodate the increased flow of the plunger. Making room for a larger valve meant removing material from the core of the fluid end, leaving it weaker and more prone to failure.
Cat XD fluid ends pair a larger plunger with a smaller, more efficient valve—running a 4.5-inch plunger with a 4-series valve without sacrificing rate. Cat valves offer higher lift and obstruct fluid flow less then other valves on the market, resulting in a 4-series valve that performs like a 5-series one.
With Cat XD Stainless Steel fluid ends, you get more material for fatigue resistance plus increased flow rates for all plunger sizes. Talk to your Cat dealer about putting these fluid ends to work in your application—and start seeing improvements in uptime and life.