single-piece 1st stage piston, installed with new rider rings using a material optimized for dry-running, high speed and high load applications. These would be matched with a specialist coating applied to the piston rod and a new cylinder liner, designed by Burckhardt Compression. These improvements were projected to increase the mean time between overhaul( MTBO) from 8,000 hours to more than 24,000 hours.
Due to the perlite being carried over to the 2nd stage, and on occasions to the 3rd stage, all the sealing rings were upgraded to the proprietary material from Burckhardt Compression. Since the upgrade was completed, the 1st stage rings have a minimum service life of 24,000 hours, while those in the 2nd and 3rd stages have been checked and reinstated, achieving over 72,000 hours of reliable service.
Process modifications In another example, an LNG terminal had a process that needed the compressors to start and stop frequently. While they were coming up to speed, the operation needed to flare the gas. This had both a financial cost as well as environmental implications and required regular dialogue with the local authorities.
Predominantly, the duty compressor would run at 50 % capacity while the stand-by unit remained offline. Each month, the compressors would switch operations to rotate the duty cycle and share the running interval. Each time the duty compressor came online, the operator was flaring the gas for up to an hour before the gas temperature was stable and low enough to prevent high-temperature trips.
Eliminating the need to flare The review found that the process had a desuperheater that was operating in bypass mode, so the first cooling step was not being used fully. This caused an extended cooling time, during which the gas had to be flared. By adopting a different procedure where the compressor runs in bypass mode and using the desuperheater, there would be no need to flare the gas.
In addition, Burckhardt Compression recommended modifying the start-up sequence when both compressors were needed to meet demand. As part of the comprehensive review, further suggestions were made to improve the packing to reduce leakages. Further recommendations on components that would improve reliability and ease of maintenance, such as valve covers with pressure bolts and improved bearing design for increased load bearing capacity were submitted. This revised operating process could make a significant reduction, around 25 tonnes CO2e per year, in the carbon footprint of the terminal and will also cut the financial
losses of burning the gas. In addition, these changes would minimize the risk of environmental fines, at a time when local legislation was being tightened.
Trusting in decades of expertise At a time when LNG operations are under increasing scrutiny from an environmental standpoint a process review, even on a relatively new installation, can deliver improvements and cost reductions. For older installations, a review of legacy parts can reveal opportunities for improvements in terms of both materials and design.
Burckhardt Compression has developed its BC ACTIVATE assessment program, which analyzes and evaluates a reciprocating compressor from any manufacturer and delivers a series of recommendations for improvements. Extensive data collection and analysis, coupled with decades of experience, result in a range of solutions that will improve performance, reliability and service life.
While operators of reciprocating compressors can call on this expertise as required, the most effective solution is to engage in a long-term service agreement( LTSA) which adds value to the business, with improved lifecycle costs, operational efficiency and accurate preventive maintenance. Together, this partnership ensures the compressors continue to deliver dependable service, with planned outages and revamps scheduled for optimum performance.
The issue was process related, rather than a specific problem with the compressors’ design. The terminal’ s engineering team called in Burckhardt Compression to investigate and recommend a solution that would improve the situation. After a detailed discussion about the existing process and the reasons for flaring the gas, it was possible to make some recommendations.
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For further information please visit www. burckhardtcompression. com
94 PECM Issue 78