WTUI – Removing Water & Particulates from Turbine oil
4. One way to quickly remove water, particulates from turbine oil
Plant managers are challenged to deal with the unexpected during virtually every outage. For Roger Bishop, the person responsible for a LM6000-powered 3 x 1 combined cycle and other assets at South Texas Electric Cooperative Inc’s (STEC) Sam Rayburn Power Plant (Nursery, Tex), it was lube-oil contamination caused by a violent rainstorm in the middle of a January 2012 outage.
The Dresser-Rand steam turbine serving the nominal 180-MW combined cycle was down for maintenance and the rotor was out of the unit when rain hit, forcing water into the machine’s lube-oil reservoir. This happened despite having tarpaulins covering the unit. Approximately 3000 gal of expensive turbine oil was contaminated to more than 6000 ppm of water—enough to turn the fluid milky. At this level of contamination, the oil oxidation rate and machine bearing wear increases by a factor of 10, putting millions of dollars of equipment at risk.
Time and cost are major considerations during most outages. The optimal solution for Sam Rayburn was offered by Oil Filtration Systems Inc, Boerne, Tex, located about 150 miles up the road from the powerplant. Within a matter of hours, OFS had one of its Vacuum Dehydrator Oil Purification Systems (VDOPS) onsite. Its state-of-the-art filtration technology can reduce the amount of water in turbine oils to as low as 20 ppm and the concentration of particulates to meet or exceed new-oil cleanliness specifications—typically ISO 16/13/10 or better.
VDOP systems are simple to operate and require only electricity to remove particulates, dissolved gases, and water from oils. The equipment, virtually maintenance free, is designed both for fast hook-up and for 24/7 operation in outdoor environments.
Processing of the contaminated oil (Fig 1) began just before 8 p.m. the day OFS was called by STEC. The VDOPS (Fig 2) reduced the amount of water in the Sam Rayburn oil by 4000 ppm in the first hour and in less than two days achieved 45 ppm (chart). During that time, particulate matter went from 18/16/14 to 15/13/10 (Fig 3).
These results were verified by OFS’ onsite portable fluid analysis kit, which is used by technicians to chart progress and allow customers to see firsthand the improvement in the condition of their oil. Bishop said, “The Field Service Group of OFS was very knowledgeable about oil cleanliness standards and went above and beyond to get my turbine oil dehydrated and free of particulates.”
VDOP systems are designed to work on wide range of fluids used in powerplants—including hydraulic and lubricating oils, diesel fuel, phosphate ester, transformer oil, etc. They can remove 100% of free and emulsified water from these fluids, as well as 90% of the dissolved water (down to 20 ppm). Regarding solid contaminants, particle counts as low as ISO 12/10/9 can be achieved with high-efficiency 2.5 Beta(c)>1000 filter elements.
In addition, the VDOPS can be equipped to remove varnish, acid, and entrained air or gas as required. OFS offers contract field services and equipment rentals, as well as purchase options. Several units are assigned to strategic locations to allow a rapid response for the company’s field service business. CCJ
