These seal-free, lube-free bearings strengthen pump equipment and reduce downtime.
by Rob Judd
August 24, 2015

Pumping abrasive fluids is always a challenge for applications operating in harsh environments. Seal or bearing failure can damage or even destroy sensitive equipment. Cost and equipment downtime are always an important consideration in balancing any project's success or failure.

Transfer pumps, electric submersible pumps (ESP), stationary pumps, vertical turbine pumps, dredging pumps and injection pumps all operate in demanding and abrasive environments. A typical sealed bearing must be kept clean and lubricated for the pump to operate appropriately. Even the smallest break in the bearing seal can quickly flood the bearing with abrasive working fluids, bringing pumping operations to a halt.

Diamond Bearings

Diamond bearing technology offers an innovative solution for pumping applications operating in harsh environments. These seal-free, lube-free bearings strengthen pump equipment and reduce downtime. This advanced diamond technology provides a high-performance alternative to conventional roller or plain bearings and is ideal for operation in process fluids where abrasive particles can cause accelerated wear.

Diamond bearingsImage 1. Diamond bearings deliver the longest production life possible, helping operators work longer and reduce overall costs. (Images and graphics courtesy of US Synthetic Bearings)

Polycrystalline diamond (PCD) is the key to success in these harsh environments. PCD is diamond grit that has been bonded under high-pressure, high-temperature conditions. Typically, PCD is bonded to a tungsten carbide substrate during high-temperature, high-pressure processing. PCD delivers extreme hardness, wear resistance and high thermal conductivity.

From a technical standpoint, diamond is resistant to all corrosive and erosive environments. It easily operates in any chemical or process fluid and is resistant to all acids and bases. It combines fracture toughness and hardness for improved durability compared with other engineering materials. It also offers a lower coefficient of friction than tungsten carbide, steel and polytetrafluoroethylene (PTFE).

Because of diamond's unique material properties, PCD bearings often deliver increased life over other bearing technology. Applications currently benefiting from PCD bearing technology include the following:

  • Mud motors: These motors are commonly used in downhole drilling applications. In operation, they force particle-laden mud through diamond radial and thrust bearings within the drill string. The main benefits in these applications are the life of the diamond bearings and the low cost of operation compared with competitive tools that depend on less reliable traditional bearings.
  • Marine hydrokinetic (MHK): MHKs have the same architecture as vertical turbine pumps and benefit from the seal-free advantages of diamond bearings. In renewable energy, the biggest challenge facing this type of system is the abrasive particles in the water running through the underwater turbine rotor. During initial testing, engineers mixed sand and gravel into the water and then ran it through the PCD bearing to see how the bearing would perform. The diamond bearings simply ground up the particles with no measureable wear.
  • Subsea motors: The challenge with this application is the oil contamination from traditional bearings and the significant forces on the pump impeller. By employing diamond bearing technology, engineers can design tools that better handle these forces on the impeller. The diamond material also allows engineers to reduce the overall size of the motor and pump configuration during the design phase of the project.
Physical and mechanical property comparisonTable 1. Physical and mechanical property comparison
*ASI 4140 Steel, annealed at 815 C (1,500 F) furnace cooled 11 C (20 F)/hour to 665 C (1230 F), air cooled, 25 millimeters (1 inch) round (1,100 F) temper
** PCD on PCD in H\sub 2\nosupersub O, dynamic, dynamic
†Tungsten Carbide on Tungsten Carbide, static
‡Steel (hard) on steel (hard), dynamic
YAt 100 C

Compared with traditional bearing technology, diamond bearings offer extended bearing life by four to 10 times in the harshest environments. Diamond is known for its high thermal conductivity and low coefficient of friction.

During starting and stopping, high thermal conductivity reduces the likelihood of causing localized welding of the surfaces, which in turn leads to scoring and galling of the bearing surface. In sliding-element bearings, low coefficients of friction decrease heat generation and reduce power losses.

Diamond bearings deliver the longest production life possible, helping operators work longer and reduce overall costs. They hold up under demanding conditions and abrasive environments. They are designed to carry extreme loads and accommodate high speeds in a compact, robust, simple design that permits process fluid lubrication—greatly reducing the need for seals.