The Future
Advances in computer technology are encroaching on all aspects of everyday life and so it is inevitable that these will be extended further into the area of machine controls and monitoring. Micro-processor controllers are already available for individual machines. These provide not only data relating to various pressures and temperatures whilst the machine is running but also record and store readings when fault conditions arise, thus simplifying troubleshooting.
On compressors, which we have supplied to FPSO vessels, for the oil & gas industry, all such data is transmitted to a central Unified Automation System computer. All machinery is continually monitored and controlled by the UAS. No doubt such systems will become commonplace on other vessels as the price for such systems fall. With advanced communications, Superintendents will download data directly to their p.c's and advise their shipborne colleagues on the recommended course of action. The computers however will still not de-coke the valves, so what can be done to reduce the workload ?
Bearing in mind the advantages of the rotary screw compressor, the obvious solution would be to use a screw compressor for engine starting duty. The problem is that most screw compressors only operate at about 12 bar, whilst 30 bar is needed for starting air. Screw compressors have been built which are suitable for this pressure (2 stage type) but the problem is that the capacity is too large for starting air applications. Sealing an air screw end at 30 bar requires considerable mechanical strength, which in turn requires a certain minimum size. In real terms this equates to 700〜800 m3/hr, which is too large for marine starting duty.
Tanabe have produced an alternative solution with the SP compressor. This 2 stage machine has a single motor, with the shaft extended at each end. One side drives a rotary screw compressor, whilst the other sides drives a reciprocating booster compressor. This system significantly reduces maintenance time, extending overhaul times to 5000 hours compared to 1500 hours for most competitors using wholly reciprocating compressors.
