Mud Pump Belt Drive Basics

Oilfield mud pumps have a tough job to perform, and so do the belts that drive them. Single and double electric motor and diesel engine driven pumps can generate 1,600 horsepower per drive and more. Speed ratios can range as high as 4:1. The center distance between sheaves or pulleys is long and the load on the belts is high. How can what is essentially a rubber strand transmit enormous power from a motor to a driven shaft?

The answer lies in the design of the modern industrial belt.

A Brief Perspective

During the Industrial Revolution, gears, roller chain and flat belts were the primary means used to transmit power. Flat belts relied entirely on friction. The belts could easily slip and walk off the pulley. They were short-lived and limited in the amount of power they could convey.

In 1917, John Gates invented the reinforced rubber V-belt. This innovation transformed belt drive technology. In the 1940s, synchronous belts (known as timing belts) were invented. Synchronous belts are toothed belts that run on toothed sprockets. They represented another leap forward in belt technology. Synchronous belts now compete head-to-head with roller chain and gear drives in most industrial applications. This article will focus on the V-belt, the type most commonly found on mud pump drives.

Principles of V-Belt Operation

V-belts are designed to transmit power via pulleys, or sheaves. V-belts have a V-shaped cross section that wedges into a corresponding V-shaped groove in the sheave or pulley, and this V-shaped groove holds the belt in place. The rubber core makes the belt flexible, so it can bend around the sheaves. High strength tensile members, or cord, transmit power from one pulley to another. And fabric reinforcement layers protect the belt from the environment and add strength.

The V-belt is a tension-wedge device. When tension is applied to the belt, it causes a wedging action. The vertical force applied perpendicular to the belt top (Fv) is transmitted via normal forces to the belt sidewalls (FN) as shown in Figure 1. The wedging force is related to the angle of the pulleys using trigonometry. Friction between the belt sidewalls and the sidewalls of the sheave groove transmit power. The amount of force or torque transmitted depends on the friction force generated.