Turbine Oil Bleed & Feed: A Very Expensive Option

The industry standard for determining when to change your turbine oil is when the antioxidants deplete to 25% of their original level. An accepted practice to extend the life of your turbine oil has been “bleed and feed”. Bleed and Feed is the practice of discarding a fraction of old oil and replacing it with new oil. Often 20-30% of the oil reservoir volume will be exchanged with new oil. This practice has become so widely adopted that few plants even pause to determine the economics of bleed and feed.

Protecting high-speed turbomachinery

Fouling of the main oil tanks can cause serious problems in high speed machinery as these impurities can flow inside the bearings. This can cause rupture and friction within internal bearing parts such as the tilting pads or the journal parts of shaft, as well as damaging internal components of the lube oil pump. Oil filters are mainly used to remove these impurities and particulate.

Excessive return oil flow in a compressor train installation

This compressor oil flow case study by Kevin D. Yates, a rotating equipment specialist at The Dow Chemical Company in Freeport, Texas, was presented at the 42nd Turbomachinery Symposium in Texas. The case study is about a new motor-gear-compressor train installation in which the lube oil pressure became an issue during commissioning and startup.

Innovative solutions to address lube varnish in hydrogen seals

Hydrogen is the medium of choice for cooling about 70 percent of electric power generators over 60MW. It is more efficient for dissipating the heat load in generators compared to water, air or oil. Most large frame gas turbine models use hydrogen as cooling medium for their generators. Oil, often the same turbine oil used for bearing lubrication, is used as an occlusive seal to keep the small molecules of hydrogen gas from leaking down the shaft and out of the generator.

Lubricating rolling element bearings using oil mist

For rolling element bearings that are not lubricated by a forced lubrication system, there are a few methods available to the user. Oil mist has been presented as the best method of lubricating bearings. It is the best and has some advantages.

How to increase varnish mitigation performance by incorporating customizable ESP media

Interpreting results for the new ASTM standard for varnish potential

Turbine oil varnish has been a well-documented reliability challenge for power plants. Traditional oil analysis techniques have been ineffective at predicting the onset of deposit problems in turbine oils – often defined as varnish. This has led to the commercialization of several new analytical tests which measures oil degradation products and can be correlated to the potential of deposit formation of turbine oil. The most widely adopted test is referred to as Membrane Patch Colorimetry (MPC).

When selecting turbine oils, look beyond the spec sheet

Turbine lubrication practical tips

Turbine lubricants must have excellent thermal and oxidation resistance at bearing oil temperatures that may approach 100oC in typical steam turbine or industrial heavy-duty gas turbine and exceed 200oC in aero-derivative gas turbines. Turbine lubricants must control the rust and corrosion that could destroy precision surfaces, resist foaming and air entrainment, which could impair lubrication and lead to equipment breakdown, and have high viscosity indexes that allow more uniform lubricating performance over a wide range of ambient and operating temperatures.

Measuring Turbine Oil Varnish Potential

Performing oil analysis tests to determine the presence of varnish in a system is challenging for a few reasons.  The sample of oil that is obtained for analysis may not be indicative of the condition of the lubricating system. If the lubricant in a heavily varnished system is changed without performing a flush to remove the deposits, the new oil may initially indicate a low varnish potential even though there are deposits throughout the system.

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