BASF is one of the world’s largest diversified chemical companies. At their plant in Freeport, Texas, they operate an Ingersoll Rand HSE-2-NL non-lube compressor in hydrogen service.
Without lubrication, the conditions within the cylinders can radically enhance wear, causing extreme damage, especially to the rider bands.
The piston rider bands in this specific compressor were found to be wearing out far more quickly than expected, typically after five to six months of operation.
On several occasions, the accelerated
rider band wear brought the piston into
contact with the cylinder liner, resulting in
significant damage, cost and delays.
The maintenance engineers on site
recognized that some way of increasing
the service life of rider bands was urgently
required, and they consulted Cook
Compression for technical support.
Cook Compression is a licensed supplier for the Howden Thomassen Free Floating Pistons (FFP™) system in North America, and after discussions we have given demonstrations and presentations to BASF to replace its conventional compressor pistons with FFP technology.
This technical innovation allows non-lube operation while eliminating friction problems in cylinders.
As traveling back and forth in the cylinders, the FFP is lifted by a thin cushion of pressurised process gas. The gas cushion allows the piston "to float" and prevents the rider band from making contact with the cylinders.
The FFP system was developed in response to the growing use of nonlubricated compressors systems.
Today over 360 compressors are already equipped with the FFP improving rider band lifetime and making the time between maintenance longer.
The Free Floating Pistons were installed in both cylinders of the BASF hydrogen compressor in October 2011.
An inspection was carried out in February 2012. After four months of continuous running, maximum rider band wear was measured at 0.009 in. (0.23 mm). A second inspection in August 2012 showed an increased of only 0.005 in. (0.13 mm), giving total wear of 0.014 in. (0.36 mm) after 11 months of operation.
With the FFP™ system in place, rider band service life increased to 12 months. BASF officials report that the unit is continuing to operate normally and is on target to meet its expectations.
Free-floating pistons allow operators to reduce costs, avoid contamination risks, enhance reliability and availability, and in some cases even remove the need for a spare standby compressor. FFP™ users have also noted that, in addition to eliminating rider band wear, the system increases the service life of piston rings and packing case components by keeping the piston centered in the cylinder. Some also report reduced power consumption and decreased noise.
Free Floating Pistons have been in use now for almost twenty years and have shown excellent reliability.
Today, there are over 360 FFP™ systems operating worldwide.
The concept of FFP is simple, yet the implementation requires the highest standards of precision engineering.
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