The Role of Coupling Rods for Progressive Cavity Pumps

July 25, 2018

There's a prime mover on the floor, bolted to a concrete plinth. Further down the line, a progressive cavity pump is ready for its first day of work. Moving between those two key drive sections, there's the coupling rod. This is the bridging or connecting component that hooks the prime mover to the pump mechanism. Starting at the drive shaft, let's see where the powertrain takes the rotating energy.

Deconstructing the Powertrain

That prime mover is probably a powerful electric motor, a machine that's designed to rotate slowly while it delivers massive quantities of torque. It's connected to a retainer sleeve, which in turn connects to a rubber sheath. Further down the train of rotating parts, we arrive at the coupling rod. It doesn't look exactly special, but it has an important role to play in this linearly configured pump architecture. Essentially, this is the key power transmission joint. In review, energy is generated by the electric motor, torque is transmitted to the rotor of the progressive cavity pump, and it's the coupling rod that bridges the two primary drive sections.

It's Never the Weakest Link

Numerous windings and magnetic poles provide the prime mover with pure drive muscle. At the other end, a rugged elastomer is working in concert with a double-chrome plated rotor to pump an abrasive stream of fluid. They're entirely reliable equipment stages. What we don't want here is a chink in the armour, a weak link in the chain, or any other metaphorically described system shortcoming. In theory, coupling rods would be the likeliest failure zone in the equipment line. In practice, however, a stainless steel backbone ensures the connecting rod is at least as strong as any other mechanical part. Covered in grease and sealed with a chromium-strengthened finish, the interconnecting drive rod won't fail.

Coupling Rod Geometry

Let's say the short drive part is manufactured from 316 stainless steel. That's all well and good, but what's happening at the two terminating ends? It's here that the hardened bushings are locked against two anchoring sleeves. Densely fabricated coupling pins drop through the aligned holes. They're key-fitted or hammered into place until a physical connection is absolutely established. Then, like any other part of the progressive cavity pump's working parts, it can be removed for maintenance. By the way, remember to lubricate this pivotal drive component when the machinery enters a scheduled maintenance phase.

The role of a coupling rod in a progressive cavity pump is basically to perform as the gear's key mechanical linkage. It's a fairly featureless rod of stainless steel, apart from the dual bushings, and it's as much part of the equipment maintenance program as the rotor, motor, or stator.

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