In this case study, Detechtion Technologies analyzed operating conditions and identified impacts of over-compression caused by fluctuating volumes and pressures to protect and optimize a screw compressor fleet while maximizing reliability.
The Mission:
Manage a fleet of screw compressors with varying conditions & configurations to improve fleetwide runtime and reliability. Determine impact of volume ratio on the compression process and potential impacts of optimized screw compression to prevent future failures due to over-compression.
Background:
An international energy producer with assets in North America, Europe, & Australia averaged annual production of 85,000 BOE/D and had 54 active units in Enalysis with 10 additional being added in year following this case study.
A screw compressor that was not initially enrolled in Enalysis experienced multiple failures within a short time frame. The initial diagnosis from the packager was that the failures were due to inadequate lubrication. Their recommendation was to increase the volume ratio to increase the differential on the unit. Given the design of the unit and the desired operating conditions, there were multiple performance flags to address, mainly: driver horsepower and over-compression. Inspections of the multiple failures found that there were damaged bearings and play in the gears that ended up causing significant damage to the housing and the male rotor.
With over-compression, there is an inherent inefficiency present in the compression process, resulting in a power penalty. If an installed Vi is not optimal for the conditions, there is a larger horsepower requirement than a fully optimized case.
Over compression results in rapid expansion of gas in the discharge port of a screw compressor. If the internal discharge pressure within the screw compressor is larger than the line pressure, rapid expansion of gas will occur in the discharge port which can lead to, significant vibration throughout the package.
The Solution:
Leverage Detechtion’s readily available technical expertise of the screw compression process to analyze operating conditions and identify impacts of fluctuating volumes and pressures using Enalysis configuration changes and capacity control simulations.
Through data analysis of the historical operating conditions, it was initially determined by Detechtion that the unit was experiencing significant over compression due to the installed volume ratio (Vi). A reduction in the Vi ensured that the discharge pressure on the screw compressor was more closely aligned with the line pressure which would reduce the vibration and potential bearing wear associated with over compression.
This lower volume ratio was installed on the unit and the compressor put into service once again. The team also identified additional at-risk units experiencing significant over-compression and in turn recommended changes to help extend unit life and avoid potential failures. Shutdown settings were tailored to protect assets against operational flags including engine overload, over-compression, and low machine differential.
In other cases, a less expensive alternative was adopted by adding back pressure or restricting the operational suction pressure range to address the vibrational concerns with over compression.
The Impact:
The client continued to leverage Enalysis offerings to monitor and optimize their screw compressor fleet to protect against potential failure modes and maximize unit reliability and runtime.
