Session: 15-01-01: General Topics on Risk, Safety, and Reliability I

Paper Number: 164822

Root Cause of a Carbon Dioxide Compressor Incessant Tripping 

In the event of tripping of the main lube oil pump of a centrifugal compressor lube oil system in the Urea plant of a major petrochemical complex, the auxiliary lube oil pump has not been developing sufficient pressure to prevent the centrifugal compressor from tripping on low-low lube oil header pressure. All modifications implemented to solve the problem before the current investigation were not successful. The main objective of this paper is to present the result of the investigation of the incessant compressor tripping problem and the painstaking approach employed in identifying its root cause.

 

The investigation commenced with the review of the available lube oil pump datasheet/specifications to confirm that the lube oil pumps are being utilized in the field for what they were designed for. Plant operators and technicians were interviewed to have a preliminary insight into the nature of the problem. During all the simulations of changeover, the auxiliary pump did not develop sufficient lube oil main header pressure within the couple of seconds required to prevent a low main header lube oil pressure alarm and subsequent tripping of the compressor. Weak points of the lube oil system – valves, retrofitted primers etc – were opened for inspection. The main lube oil pump components that were never inspected because the pump delivers required pressure while in operation were opened during this investigation.

 

The retrofitted primer and the hole drilled in the auxiliary pump check valve disc were plugged as they were adjudged to be negatively affecting the priming of the auxiliary pump (creating vortices while the auxiliary pump is on standby). The auxiliary pump, thereafter, developed pressure but insufficient to prevent the tripping of the compressor. This development was the reason to suspect the check valve of the main lube oil pump that was considered “healthy”. The non-return valve’s spring of the main lube oil was found broken – passing lube oil during auxiliary pump operation - and replaced. The lube oil system pumps changeover was tested, in simulation mode, after all the suggested modifications were made. The auxiliary pump took-over successfully, when the main lube oil pump was manually tripped, without activating the alarm signal let alone the trip signal.

 

The novel ideas introduced in the investigations are the reversal of the retrofits introduced to the auxiliary pump (plugging of the prime line and hole drilled in the check valve disc). These actions improved the auxiliary pump performance. Another idea was the inspection of the main pump’s check valve that was considered “healthy” (never inspected before this investigation) since the main pump develops sufficient pressure. The repair of the malfunctioning main pump check valve completed the resolution of the problem.

Presenting Author: Kamorudeen Abidogun Saudi Aramco

Presenting Author Biography: Kamorudeen, a Lead Project Engineer at Saudi Aramco, is a licensed professional engineer in the State of Texas with over two decades of experience as a technical subject-matter expert / Project Engineering Consultant in the oil and gas industry, executing Engineering Design, Procurement, Construction, Commissioning and Startup activities.

Authors:

Kamorudeen Abidogun Saudi Aramco