productivity immediately. Whatever the reason, the process to identify the best solution remains the same.
The first step in revitalizing a compressor is completing a comprehensive assessment to understand the condition of the equipment, the urgency of any repairs and potential benefits of this work. Obtaining sufficient information requires a structured assessment that uses advanced measurement techniques and data analysis to identify any issues.
Using data available from the operator’ s process, as well as any additional sensors that may be required for a comprehensive picture, in-depth analysis should identify any bad actors. The major issues can be categorized into three main groups: reliability, excessive energy consumption and gas emissions.
Each group has a direct effect on the business and should be addressed methodically to deliver data-driven insights and effective solutions.
Precision measurements
The monitoring and protection of reciprocating compressors is now covered by the 5th edition of API 670, released in November 2014. Plants operating these machines will often categorize them as critical equipment and therefore put in place sensors to collect important data.
Over time, continuous operation causes clearances to go out of tolerance, which will induce vibrations. Sensors can be installed in several locations as part of the machine build or portable equipment can be used to establish vibration levels periodically. Whichever option is chosen, this data is some of the most important information needed to determine any potential issues.
Velocity sensors can also be used to determine vibration in the frame, crosshead, and cylinder. Their positioning is crucial in achieving accurate data that can be used
to pinpoint issues. Working with the OEM or a maintenance provider
A typical terminal equipped with LNG compressors
Experienced service providers can provide comprehensive revamps, including reverse engineering parts and introducing upgraded materials.
experienced in this application should ensure that all sensors are correctly located and calibrated.
Problems with valves, such as sticking or lost springs, can be isolated if crank angle data is available. This should be complemented with accelerometers and velocity sensors, which can be used to measure vibration, gas leak malfunctions and overloading.
Analyzing the options
Having established the areas of the compressor that require attention, the next step is defining the best course of action. There may be short- and long-term solutions and the operator needs to be aware of all the options. The OEM may not be able to deliver immediate support and replacement parts for older machines may have a long lead-time.
This is where an independent service provider with an OEM background could deliver alternative options. The ability to reverse engineer parts supported by all the required documentation is crucial to providing a fast response. Options can include upgrading the original material specifications as well as improving clearances and sealing solutions.
With many machines having completed decades of service, materials technologies have progressed significantly since their original design was conceived. In the intervening years, there have been many significant improvements in materials and machining technologies which can now be used to extend the service life of existing assets.
Extending piston life by 300 %
The BOG compressors at an LNG terminal were suffering from reduced reliability – the 1st stage pistons needed to be replaced every four years. The operator had approached the OEM for a solution, but they did not respond with any support. This
led to Burckhardt Compression being approached to investigate and resolve the problem.
The LNG storage tanks used perlite for insulation and in the older tanks it had come away from the tank walls and was being carried through the pipework to the compressors. In the cylinders, it acted like a grinding paste, predominantly damaging the 1st stage piston, but some perlite carried through to the 2nd stage as well.
Increased clearances and wear to the piston ring grooves caused the sealing rings to become dislodged and trapped in the valve port, causing the rings to break. The material for the rider rings had been selected poorly and all stages were missing pressure release grooves. As a result, the original rings would be changed after 8,000 hours.
New materials
The engineering study determined that the best option for an improved design would be an aluminum,
Issue 78 PECM 93