The Internal Components of Positive Displacement Motors (PDM)

Summary

This video provides a detailed breakdown of the assembly process for a mud motor, commonly used in drilling operations. It covers key components such as thrust bearings, cartridge assemblies, marine bearings, and inverter rings. The video explains the function and interaction of these parts in handling axial and radial loads while ensuring smooth rotation. It also touches on different sizes of mud motors and how the principles remain consistent despite size variations. The process culminates in the final assembly, ensuring everything is securely positioned and ready for use in drilling.

Takeaways

• 😀 Thrust bearings are essential for handling axial loads while allowing rotation in the motor components.
• 😀 The thrust bearing assembly includes two races: a stationary one at the bottom and a rotating one at the top.
• 😀 The bearing assembly uses ball bearings between the two races to allow free movement when rotated.
• 😀 The assembly involves stacking a stationary can, rotating sleeve, and ball bearings to create a cartridge.
• 😀 Marine bearings are applied to the drive shaft, with rubber bonded to the inside of a brass shell for added durability.
• 😀 Radial bearings are similar to marine bearings but have different lengths depending on their position in the assembly.
• 😀 The motor uses a bearing housing to house the stacked bearings, with a cap on top to secure the components.
• 😀 Flow restrictor cartridges, with compression springs, prevent the rotation of the stationary components in the assembly.
• 😀 The inverter ring helps flip cartridges in the assembly to ensure proper alignment, allowing for uni-directional operation.
• 😀 Mud motors come in various sizes, from 3 and 3/8 inches to 11 and a quarter inches, but the core principle behind their components is the same.

Q & A

What is the primary function of thrust bearings in a mud motor?

Thrust bearings are used to manage axial loads, allowing the components of the mud motor to rotate while handling the pressure from forces acting along the axis.

How do the different thrust bearing assemblies in a mud motor work?

There are multiple thrust bearing assemblies, such as the original canned type cartridge assembly, which consists of stationary and rotating races with ball bearings in between. These allow for smooth rotation while handling axial loads.

What is the role of the flow restrictor cartridge in the mud motor?

The flow restrictor cartridge is used to manage the flow of fluid within the motor, ensuring proper compression and preventing outside stationary components from rotating.

What is an inverter ring and why is it needed in the mud motor assembly?

An inverter ring is used in the mud motor assembly to reverse the direction of the cartridge components. This is necessary when the entire cartridge needs to be flipped for certain operations.

What is the purpose of the marine bearing in the mud motor?

Marine bearings are used to provide radial support for the drive shaft, ensuring smooth rotation while withstanding harsh conditions. They are often constructed with rubber bonded to a brass shell.

What differences exist between various sizes of mud motors?

Mud motors come in a range of sizes, from 3 and 3/8 inches to 11 and a quarter inches. While their sizes differ, the fundamental principle and components, such as thrust and marine bearings, remain the same.

How are the bearing cartridge assemblies arranged in the mud motor?

The bearing cartridges are stacked in a specific order, with some cartridges installed in a uni-directional manner. The use of an inverter ring helps to switch the direction of these components when necessary.

What materials are used for the bearings in the mud motor?

The bearings are typically made with a combination of steel races, ball bearings, and sometimes brass or rubber components, depending on whether they are thrust or marine bearings.

How is the final bearing assembly completed in the mud motor?

The final bearing assembly is completed by pressing the marine bearings into their respective bearing housings, stacking the cartridges in the correct order, and securing everything with o-rings and a bearing housing cap.

What are some key design considerations when assembling a mud motor?

Key design considerations include ensuring the proper arrangement of bearings to manage axial and radial loads, the use of flow restrictor cartridges to control fluid flow, and the placement of inverter rings to manage directionality in the system.