Lube Oil Flushing of Compressor and Air-cooled Heat Exchanger (ACHE) at RHIP, Oman.

April 25, 2020

Place of Operation: RHIP, Salalah, Oman
Date of Execution: December-2018 to April-2019
Criticality: High

Background: Prior to Minimac being involved in the project, in August 2018, as a part of the pre-commissioning activity, flushing of 14 compressors and heat exchangers (ACHE, Picture 2) was performed and completed by a service provider. But soon after in the month of October, during the commissioning of the compressor, large debris deposits were found getting generated and collected in the in-line lube oil filter. The debris consisted of silica, metal shaving, and a lot of chunky particles. The commissioning activity was immediately stalled, leading to a threat to the project timeline and subsequent financial loss for the EPC company and the Operating company - PDO.

Problem Statement: Large particle contamination detection in the inline filters of all heat exchangers and compressors during the commissioning stage, even though flushing was completed as a part of the pre-commissioning activity.

Underlying Issue: During the root cause analysis there were two reasons anticipated for this issue:
1. The Heat Exchangers were not stored properly leading to heavy particle ingress and accumulation.
2. Poor Flushing of Heat Exchangers. Most flushing service providers only consider the inlet and outlet pipe diameter of the heat exchanger (ACHE) to calculate the flushing flow rate. Mostly it is inefficient as each heat exchanger consists of multiple tubes that should be flushed with sufficient turbulent flow in each tube. As a thumb rule, for every 1” of the tube, 100 LPM of oil flow is required.

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What Minimac did:

1. A detailed root cause analysis was run and then it was suggested to flush all the heat exchangers, connecting lines and compressors once again separately, as there were multiple possibilities of particle ingression into the lube oil stream.

2. As a very large flow rate of 4000 LPM was required to flush the heat exchangers properly. Due to project timelines, 14 compressors were to be executed within a short duration, and hence 4-5 Flushing Skids of 4000 LPM (Picture 3) was set up in parallel.

3. Flushing was undertaken in 3 major stages where ACHE tubes, compressor lube oil system, interconnecting pipes were flushed individually. All sophisticated components like inline filters, bearings were by-passed using temporary loops.

4. A mesh screen inspection (as per API 614 Acceptance Criteria given in Table 1) on the return line from the client’s system was performed every 24 hours to monitor the debris on the entire flushing fluid stream. Flushing was continued for each stage until the mesh screen showed an acceptable level of debris as per API 614. (Picture 4)

5. An ISO 4406 test using a laser particle counter was also performed on the final sample of oil to ensure an ISO 15/13 cleanliness level.

Result: All 14 compressors & Heat Exchangers were flushed efficiently and an ISO 15/13 cleanliness level was maintained.