180 Strathmoor Drive Sherwood Park, AB T8H 2B7
3626 N. Frazier Industrial Park Dr Conroe, TX, USA – 77303
Suite 550, 842 West Sam Houston Parkway North, Houston, TX 77024
Singapore, 2022

Blackstone and CST’s innovative approach transformed maintenance at a butyl production plant

Date Completed





Butyl pellet production 

Equipment Type

Centrifugal Compressors – LP + HP


Ethylene Compression


6650 kW

DISCH. Power

20.5 Bara


A customer needed to safely minimize the scope of work and inspection time for a large ethylene compressor train during an upcoming shutdown of a butyl pellet production plant in Singapore.

The unit had skipped its last Major Inspection (MI) four years ago because it was running smoothly, meaning it had not been opened in the nine years since the plant’s start-up. The customer faced a critical decision: whether to conduct the MI of the compressors or to postpone it for another six years until the next scheduled plant shutdown. Performing the MI would reduce the risk of unplanned events, but it would also result in significantly higher maintenance costs and a longer shutdown period, leading to a substantial loss of production.


The Blackstone-CST answer was a proposal of a “data-driven compressor performance study” to assess the health of the compressor train and to analytically define the actual need and scope of a maintenance intervention.

The customer accepted the proposal, and a software model of the compressor train was created and fine-tuned to match the original performance curves. Using this model, the complete set of historical field data from the previous nine years of operation was processed to analyze the following Key Performance Indicators:

  • Polytropic efficiency depletion trend (as proxy of labyrinth seals wear)
  • Dry Gas Seals buffer pressure trend (as proxy of DGSs health)

As a conclusion of the study, BTS-CST recommended against opening the compressor to inspect the internals and change the labyrinth seals, but instead advised limiting the maintenance intervention to just replacing the DGS.

Customer Benefits

The customer saved approximately 2 million US dollars by reducing maintenance work, with the assurance of continued safe and reliable operation of the equipment, shortening the turnaround time, and minimizing production loss.

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