why the double row roller bearing is used?

Double row roller bearings are used when a machine needs to carry higher loads, run more rigidly, and stay accurate under tough conditions than a single‑row bearing can handle.

Core reasons they’re used

• Higher load capacity
  Two rows of rollers share the work, so the bearing can carry much higher radial loads (and, for tapered or spherical types, significant axial loads in both directions) compared with a similar‑size single‑row bearing.

• Greater stiffness and rigidity
  The double‑row layout reduces shaft deflection and improves structural stiffness, which is important for gearboxes, machine tool spindles, rolling mills, and similar precision or heavy‑duty systems.

• Better load distribution and longer life
  With two rows, the contact area is larger and the load is spread over more rolling elements, lowering stress on each roller and extending fatigue life when properly lubricated and aligned.

• Compact way to handle combined loads
  Double row tapered or spherical roller bearings can handle high radial loads plus axial loads in both directions, often replacing two opposed single‑row bearings and saving axial space and components.

• Stable performance at demanding speeds
  Optimized internal geometry and cage designs allow double row cylindrical and spherical roller bearings to run smoothly at relatively high speeds while still carrying heavy loads.

Where you typically see them

• Gearboxes and drive units (industrial, wind turbine, steel mill) where high radial load and rigidity are critical.

• Rolling mills and steel/metal processing equipment, which impose large, fluctuating radial loads.

• Machine tool spindles, where accurate shaft positioning and minimal vibration are needed under load.

• Mining, construction, cranes, and large agricultural machinery that work under heavy, shock or continuous loads.

Quick forum-style takeaway

If your design needs a bearing that can “take a beating” in terms of radial (and often axial) load, hold the shaft straight, and still fit in a relatively compact space, you choose a double row roller bearing instead of a single‑row. It’s the go‑to option for heavy‑duty, high‑rigidity, long‑life applications.

TL;DR: Double row roller bearings are used because they carry more load, are stiffer, and last longer in heavy or precision applications, often replacing two single‑row bearings in a tighter, more robust package.

Information gathered from public forums or data available on the internet and portrayed here.