Precision Shaft, Rotor & Bearing Assembly System

Revision D Rotor & Shaft Architecture

HERPS-VOL-03 defines the complete Revision D pump rotor, shaft and rotating-assembly baseline for the horizontal three-stage centrifugal pump. The shaft transmits torque from the main SynRM drive through the spacer coupling to the three pump impellers while simultaneously carrying hydraulic radial loads, residual axial thrust, rotor weight, coupling loads, residual unbalance and transient torsional loading.

Precision Shaft Geometry & Runout Control

Revision D establishes tightly controlled shaft and journal geometry so that the complete rotor remains compatible with the bearing, seal, impeller, coupling and casing interfaces.

Three-Stage Rotating Assembly

The rotating stack includes three impellers installed in the controlled Stage 1, Stage 2 and Stage 3 sequence on the Revision D stepped shaft. Each impeller retains an 80 H7 bore and a 95 mm axial envelope.

The current mechanical impeller outside-diameter envelope is approximately 290–310 mm, with the final hydraulic surface and exact operating geometry remaining controlled by the hydraulic CFD and prototype validation program.

• Stage 1 impeller
• Stage 2 impeller
• Stage 3 impeller
• Interstage shaft sections and spacers
• Replaceable seal sleeves
• Balance-drum assembly
• Axial retention and positive locking features
• Coupling-side mechanical interface

Rotor Balancing & Rotordynamic Control

Individual rotating components are controlled during manufacture and the assembled rotor is dynamically balanced to G2.5 or tighter where the Revision D rotordynamic validation requires.

The complete bearing, shaft, coupling, impeller and support model is evaluated over the released 1,500–3,600 rpm operating envelope. Any unacceptable critical-speed or resonance regions identified by validation are excluded from continuous operation through the variable-frequency-drive control system.

Revision D Bearing Architecture

HERPS-VOL-04 retains a two-support bearing arrangement consisting of a drive-end locating pair and a non-drive-end floating cylindrical roller bearing.

Axial Thrust & Thermal-Growth Management

The three-stage hydraulic assembly generates axial thrust that is partially counteracted by the balance-drum system. The resulting residual axial thrust is carried by the drive-end back-to-back angular-contact bearing pair.

The non-drive-end cylindrical roller bearing remains a true floating radial support and is not used as a second fixed axial location. This allows differential shaft growth to occur without generating unintended thermal thrust.

The steady-state axial movement target at the locating-bearing system is ≤0.15 mm after thermal stabilization, while the NDE bearing accommodates the required differential growth.

Bearing Housing Architecture

Bearing Lubrication System

Both bearing housings use an oil-bath lubrication architecture. ISO VG46 is the Revision D development baseline, with the final viscosity grade and selected lubricant remaining subject to bearing OEM and bearing-life validation.

Labyrinth & Shaft-Sealing Interface

Each bearing housing interfaces with the rotating shaft through an approximately Ø80 mm labyrinth interface. The Revision D radial development-clearance baseline is 0.25–0.35 mm.

Final labyrinth clearance remains validation-controlled against shaft runout, bearing movement, thermal growth, rotor deflection and manufacturing tolerance stack so that no rubbing occurs throughout the released operating range.

Temperature & Vibration Monitoring

Revision D integrates dedicated temperature and vibration monitoring directly into the bearing architecture.

Rotor Assembly Sequence

1. Verify shaft identification, material certification, dimensional report, straightness, journal TIR and cleanliness.
2. Install the drive-end shaft sleeve and associated seal interfaces.
3. Install the Stage 1 impeller and approved torque-transmission / axial-retention system.
4. Install the coordinated interstage spacer and retention hardware.
5. Install the Stage 2 impeller.
6. Install the Stage 3 impeller.
7. Install the balance drum and its associated retention components.
8. Install the non-drive-end sleeve and service-end retention components.
9. Measure the assembled axial stack, stage locations and runout at journals, seal tracks and impeller reference diameters.
10. Verify free rotation with no contact at impeller tips, wear rings, balance drum, seals or labyrinth interfaces.
11. Complete final rotor balancing to G2.5 or the tighter value released by the rotordynamic validation.

Rotating-System Failure Controls

FAT & Commissioning Acceptance

• Correct approved lubricant and operating oil level.
• Free manual rotation with no bearing roughness or labyrinth contact.
• Stabilized bearing temperatures within selected OEM limits.
• Controlled speed sweep with no prohibited continuous resonance.
• Stable DE axial location after thermal stabilization.
• Verified NDE thermal float.
• All three Pt100 temperature channels operational.
• All four vibration channels operational.
• Condition-monitoring baseline signatures stored.
• Required shaft-grounding / insulated-bearing provisions installed and verified.
• No abnormal noise, rubbing, oil aeration, leakage, discoloration or excessive magnetic debris after testing.