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BB2-Radially
SplitCentrifugal Pump

Maintenance, Repair, & Overhaul

Plant Petrochemical Plant
Equipment Centre Line Mounted BB2 Centrifugal Pump
Application Benzene - Absorber Recycle Pump
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Plant Petrochemical Plant
Equipment Centre Line Mounted BB2 Centrifugal Pump
Application Benzene - Absorber Recycle Pump

Problem Statement

Centre Line Mounted - BB2 - Radially Split Centrifugal Pump failed to maintain Extended Operational Hours due to frequent disruptions caused by High Vibration (above 70 microns), abnormal oil conditions, and multiple seal failures.

During the evaluation, it was identified that the Vibration Probe Tracks had been Chrome-Plated by the previous service provider during the Pump Overhauling Phase.

Additionally, the Thrust Bearing Assembly was Improperly Configured and Exhibited Thermal Degradation due to contact between the oil ring and the oil mist tubing. Our team of specialists and engineers meticulously documented all identified minor and major issues.

Scope of Work

  • The Impeller Wear Rings had score marks evident due to incorrect concentricity and were polished during the Complete Overhauling Process.
  • The thrust bearing assembly was found to be contaminated, likely due to the oil mist tube contacting the oil thrower and thrust spacer ring.
  • The thrust bearing spacer showed discoloration heat marks caused by contact between the oil ring and the oil mist tubing.
  • The pump was Thoroughly Cleaned, and all required Diametrical and Runout checks were performed.
  • Deviations were noted on the pump casing; stuffing box covers and bearing brackets, and registers.
  • The Stuffing Box Covers and Bearing Brackets Underwent Weld Buildup and were machined to OEM specifications.
  • The final machining of the stuffing box DE/NDE was accomplished on the boring mill with the casing assembled in position on the pump.
  • The Bearing Brackets DE/NDE were also Final Machined on the Boring Mill While Attached to the stuffing box, a final runout check performed on bearing housing with reference to pump center bush.
  • The Pump Shaft, which was chrome-plated by the previous vendor during the pump overhauling phase, was rejected by the client and TESCO Engineering. The client supplied a new shaft from the OEM, which we found to have high electrical runout, requiring Correction Through Diamond Burnishing on the probe tracks’ landing to bring it back to acceptable tolerance.
  • After probe tracks were Burnished by Diamond Tip to the required surface finish, and the electrical runout was found to be within the required tolerances, which was witnessed by Client.
  • The Rotor Assembly was Balanced according to specification ISO 1940-1 (G 1).
  • The Final Diametrical Measurements were performed.
  • The existing Mechanical Shaft Seal Configuration was upgraded, from Carbon to Silicon Carbide, hard faces.
  • The replacement Mechanical Shaft Seals and Bearing Isolators were installed.
  • The pump was Assembled With a Replacement Set of Radial Bearings on both the DE and NDE sides. Thereafter, the Blue Match, plastic gauge, and bearing crush check were performed, and bearing clearance was verified, indicating that both radial bearing clearances were within the recommended range and were then verified by TESCO Engineering and Client.
  • The Pump casing was pressure tested to 2 Bar, and the seals were tested to 10 Bar static pressure test only.
  • The Pump was installed on site, the shaft alignment, DBSE and pipe stress were verified during installation.
  • The field instruments were verified and tested during installation and there was some communication errors noted which were rectified by TESCO Engineering’s Instrumentation Specialist at the time to ensure the reliablereinstatement of the pump.
  • The NDE vibration sensor, along with the probe holder, was removed, inspected, and swapped from X to Y due to incorrect installation. Gap voltage was adjusted to -10 VDC, and readings verified from the DCS were found to be healthy and within tolerance.
  • Vibration loop tags were verified one by one from the field to the DCS, as well as in System #1, and all tag numbers matched according to the vibration monitoring schematic.
Spread two fingers to zoom in
  • The triad cable’s overhaul ground shield (from the field vibration JB to the MMS rack) had been wrongly connected in the field junction box, which caused vibration fluctuation issues due to electrical noise. After correcting the Overhaul Shield/Ground Wire, all vibration readings became healthy and steady. Please see the PI trends snapshot on the right.
  • TESCO Engineering’s Instrumentation Specialist shared the finding and learnings and corrective actions to Prevent Future Errors.

Upgraded Mechanical Seals

Operational Conditions

Fluid Benzene, Flammable, Toxic
Temperature 127 C˚
Specific Gravity 0.745
Viscosity 0.18 CP
Discharge Pressure 58.04 Kg/cm²
RPM 3540

Specs

Seal Size 4.125 / 4.000
Seal Configuration Dual Pressurize-Face-To-Back Cartridge
API Plan 21 / 53C / 61

Reason for Premature Seal Failure

The Existing Seal Face Combination (carbon vs. silicon carbide) was subjected to high differential pressure on the outboard seals. This Led To Deformation of the carbon seal faces, resulting in a High Leakage Rate on the atmospheric side, which, in turn, increased the refilling frequency of the Plan API Plan 53C (every 14 days).

Solution

The Existing Inboard and Outboard Seal Rotating Faces, made of antimony carbon material, were upgraded to sintered silicon carbide hard face material. The new design incorporated silicon carbide seal faces to better withstand High Differential Pressure, Reducing Seal Face Bending and Shearing. This modification resulted in a reduced refilling frequency of 45 days.

Result

Our Fluid & Gas Sealing and Rotating Equipment Specialists meticulously conducted the Dismantling, Mechanical Seal Upgrade, Concentricity Correction, 
Re-assembly, while the IBM Team oversaw the Installation, and Commissioning 
of the BB2 Radially Split Centrifugal Pump within a span of three weeks which the OEM had failed to address twice since 2018.

The pump has since been operating reliably for over a year in the Benzene Absorber Recycle Application, demonstrating sustained performance under demanding operational conditions.

Leveraging TESCO Engineering’s strategic proximity to the operational plant, the client benefited from minimized Plant Downtime and a Highly Cost-effective, Precision-Engineered Solution.

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