trash pump filter

Why Pumps Fail Part 5: Gearbox Design

Why Slurry Pump Gearboxes Can Fail

For our final installment, we discuss gearbox design as a contributing factor to pump failure. Gears, teeth and bearings are subjected to a lot of localized stress, particularly under continuous-duty operations. Pushing and pulling, stopping and starting, thrust loading and axial forces relentlessly pound these components. You’re moving frac fluid against incredible pressures. When you near the end of a frac stage and stop your engine, that pressure can push back hard. And gears don’t like it one bit.

Keep in mind, some platforms don’t even use gearboxes, opting instead for bull-gear pinions. So on top of the stress, these pumps must also contend with timing and alignment issues. A helical gear set needs to be addressed for timing and is subject to stress resulting from opposing axial forces.

When a gear fails, you’re facing costly, time-consuming repairs. Also, you run the risk of launching components and other debris as the drive shaft continues spinning, endangering assets and people.

On the QEM 3000, Weir engineers designed a reinforced steel gearbox with double-helical gears, a balanced configuration that nullifies opposing axial forces. Reinforced steel housing not only ensures that everything is contained, but features a thickened geometry to better absorb and distribute thrust load, particularly on the parallel section. We also added bearings designed to handle added thrust loads, and torque arms - which are mounted to reduce deflection and transfer thrust loads into the main structure.

Finally, we internalized the lubrication system. Instead of the typical 10-12 exposed lubrication hoses—which are frequently damaged and consequently leak—the QEM 3000 has one input line and one drain line. This further maintains the integrity of the lubrication system, which, if you remember from our first installment, is the number-one cause of pump failure. We’ve come full circle.

In engineering the QEM 3000, Weir’s methodology was not merely to revisit the pump, but to revisit the problem, in this case the specific circumstances that contribute most frequently to pump failure. As a result of our approach, we have built from the ground up a frac pump designed to operate—and more importantly, endure—in the real world.

Simply put, the QEM 3000 is as real as it gets.