| Turbine technology
areas can need extended cleaning durations, up to one month.
“Our analysis of data from laboratory testing and field trials of the Texaco VARTECH Industrial System Cleaner has shown a number of benefits, in contrast to other conventional cleaners, highlighting our intention to introduce a system that could clean efficiently without creating operational constraints.
“First, VARTECH is compatible with many in- service oils at the recommended concentrations of 5-20% by volume for the recommended cleaning durations (allowing longer residence times and generally removing the need for flushing).
“It has also been shown to help reduce filter plugging and contribute to deposit removal effectiveness as well as being designed to help dissolve varnish deposits from internal surfaces which then helps stabilise them for removal with the used oil.
“Finally, it has a viscosity of 53 cSt which helps make it effective in ISO 32-68 viscosity oil as it will not significantly affect oil viscosity at the recommended concentrations and has a minimal impact on both lubricant water separability and on long term new oil performance in residual amounts up to 2%.”
VARTECH technology field trials One of the greatest difficulties with varnish is that much of the time it can go unnoticed within a system. Components, reservoirs, and filters continue to function, but may not be functioning as efficiently as they once were. As varnish worsens, a vicious cycle is often set in motion. The coating insulates metal surfaces which prevents efficient oil cooling and raises the temperature. This causes more degradation and less effective lubrication. More precursors are created, more varnish layers are formed and the problem spirals towards equipment failure. This was the case in one of VARTECH’s first field trials in the USA. Operating gas turbine equipment in challenging climatic environments such as the high temperatures experienced in California’s Central Valley (typically between 30º and 40ºC), is bound to produce additional challenges. Chevron San Joaquin Valley Business Unit (SJV) operates more than 16 000 wells, producing 159 000 barrels of crude and 53 million cubic feet of natural gas a day. SJV has world-class heavy crude oil steam flooding expertise, simultaneously producing steam and electricity. The steam facilitates oil recovery using the steam flooding process and the electricity is sold to a power utility. During summer the gas turbine bearings were running too hot for the turbine to operate at its full capacity, in fact, it could only produce 3.3 MWe, significantly below its 5.5 MWe design capacity. High ambient temperatures were part of the problem, but the team suspected varnish was also interfering with efficiency of the oil coolers, an issue subsequently confirmed following a visual inspection. To address the ongoing problem, the Texaco VARTECH team, led by Paul Sly, global industrial OEM specialist, changed the oil filters, replaced 15% of the used in-service oil with
Texaco VARTECH Industrial System Cleaner and then restarted the system. As the gas turbine approached full capacity, it was apparent that something had radically changed. All system temperatures remained within the acceptable range and no alarms were triggered. The gas turbine continued at full capacity for two weeks with no high-temperature alarms, then the mixture of used in-service turbine oil and VARTECH Industrial System Cleaner was drained. The system was flushed, the filters replaced, and the system refilled with Texaco GST turbine oil. The result is that SJV can operate its co-generation equipment at full capacity year-round no matter the ambient temperature, thereby gaining over $350 000 of previously lost revenue per year. A further opportunity to trial VARTECH technology came about in one of the largest oil fields in the Gulf of Mexico. Loss of power generation in any circumstance is costly and to be avoided where possible, but when it is powering a spar floating platform sitting in 4100 feet of water, 190 miles off the US coast, loss of electricity could lead to the shutdown of the whole operation. When hydrocarbon production was threatened by oil headers in the generator sets consistently running hot and triggering high-temperature alarms, Texaco’s new VARTECH technology was instrumental in providing a long-
term solution. Using VARTECH technology has not only helped the operator save up to $81 000 in annual maintenance costs but has also helped to reduce safety exposure and environmental risk by not having to remove equipment. Twelve months after first employing VARTECH technology at the Tahiti spar platform there have been no high temperature alarms and therefore no premature system shutdowns.
Moving away from dated methods Paul Sly concludes: “We are all fully aware that the lost revenue caused by unplanned or longer than expected shut down can be extensive. Our challenge was to create a solution that moved away from relying on varnish filtration and dated cleaning methods. The utilisation of the VARTECH two-step programme, in conjunction with our LubeWatch oil monitoring has seen companies successfully change their maintenance process to remove deposited varnish more effectively before they fill their systems with new oil. “Our VARTECH holistic varnish solution has shown strong deposit removal effectiveness and deposit resistance with GST Advantage Turbine oil products in extensive comparative laboratory and field testing. This improves system deposit control and cleanliness, helping to deliver longer oil life and helping to improve turbine operation.”
Above: Steel plate with varnish film (left), and after cleaning with VARTECH
www.modernpowersystems.com | March 2022 | 37
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