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Showing posts from December, 2021

Turbomachinery failures

BY AMIN ALMASI. There are many reasons for turbomachinery problems and failures. Resonance, for example, is often overlooked.  Rotating parts and components such as impellers and blade rows could be in resonance with any excitations generated by turbomachinery. Resonances for the first and second natural frequencies can be dangerous. Generally, there could be numerous cases of resonance. The second natural frequency of a rotating component, in one example, proved to be almost exactly an integer multiple of the first natural frequency. This led to excitation and operational problems. Fluid-induced vibration, oscillatory changes of fluid pressure, and turbulent flow (vortex formation) might also cause high vibration or even failure.  Fatigue, too, is often a root cause in failures of rotating parts. Individual stress amplitudes should be analyzed to ensure associated components will not fail due to different forms of fatigue such as high-cycle fatigue (HCF) and low-cycle fatigue (LCF). 

DRY GAS SEALS: How to Implement Proactive Monitoring

BY MICHAEL FORSTHOFFER. In the last 10+ years there has been a significant increase in the technology and instrumentation used on dry gas seal systems to monitor the condition of the seals. Most notable has been the call to monitor secondary seal condition – there have been significant failures of the secondary seal without any issue with the primary seal. The majority of these failures have been due to oil migration across the separation seals. As the oil is not drained out, it accumulates around the secondary seal, fills the grooves, and causes the secondary seal faces to contact. There are various approaches to monitoring secondary seal condition. Probably the most beneficial is utilizing a back pressure control valve in the primary vent (Figure). Figure: Using a back pressure control valve in the primary vent as part of the monitoring of secondary seal condition in a dry gas seal. This sets the primary vent at a pressure below the primary seal gas supply pressure, but high en

Gas Compression: Boosting Capacity at a Compression Plant

BY TALAL AL-RASHIDI & HAMAD K. AL-RUZIHI T wo multistage 16,000 HP electrical motors are used to drive two onshore gas compressors feeding a gas plant commissioned in 1984 (Figure 1). Figure 1: Onshore compressor skid . These compressors needed to produce gas at a higher capacity. Unfortunately, the existing units were unable to meet the new demand. One option considered was purchasing and installing an additional compressor. Engineers also evaluated the possibility of utilizing the available capacity of adjacent o ff shore compressors. Although onshore and o ff shore gas compressors are located on the same platform and discharge to a common header, they were designed to process di ff erent gas molecular weights due to separate feeds for onshore and o ff shore units (Figure 2). Figure 2: Compressor flow schematics. The challenge was to ensure that o ff shore compressors could handle not only the new capacity but the new gas conditions. As the plant receives gas from two associa

The Defnition of Maintenance 4.0

Maintenance 4.0 is the application of Industry 4.0 to operations and maintenance (O&M) activities. The goal is simple: To maximize production uptime by eliminating unplanned, reactive maintenance. Let’s look at a simplistic depiction of common O&M work streams. Figure 1 shows a graph depicting the activities that occur after an industrial asset unexpectedly fails.   Figure 1: O&M work streams in Industry 3.0 vs Industry 4.0 Once the failure event occurs and is reported, a series of activities occurs. First, repair crews are assigned and then travel to the worksite where they receive repair instructions. Parts must be ordered and transported to the site. Typically, root cause analysis (RCA) is performed and valuable time expended on identifying it. Working under pressure to resume production, work crews engage in trial and error activities to identify the cause of the failure. After repairs and an inspection, production resumes. Maintenance 4.0 brings artificial

RESOLVING VARNISH CHALLENGES: Varnish Removal Technology in Turbine Oil

BY HASANUR JAMAL MOLLA, SAAD H. AL-DOSSARY, TARIQ NADEEM, AND MOHAMMAD F. AL-SHIHRI. V arnish is an organic residue produced by irreversible chemical degradation of mineral oil lubricants. It can lead to filter plugging, restricted oil flow, poor heat transfer, valve sticking, fail-to-start conditions, and unit trips. Varnish on Spool Valves Varnish on gear Varnish on Journal  Bearing During rotating equipment operation, heat generated due to friction degrades the oil and produces very small byproduct particles that settle throughout the system as varnish. Spark discharges from static charge buildup in the lubricating oil filters play a key role in its formation. Over time, these particles attach themselves to surfaces throughout the turbine, producing a sticky film. As varnish builds up, performance of rotating equipment su ff ers. A variety of varnish removal systems are available in the market. As the conversion between soluble and insoluble varnish is a physical equilibrium

Corrosion Inhibiting Dry Film Lubricants

KEY TAKEAWAYS Dry film lubricants are able to face the challenge of providing the corrosion resistant lubrication required for machines operating in extreme conditions such as under heavy loads and at very high or low temperatures. From a lubrication point of view, extreme operational conditions may not commonly occur in every industry, but in some sectors such as defense and aerospace they are encountered quite often. These challenging conditions may include: Very high or very low temperatures Variable temperatures High or low surface speeds on shafts The presence of a vacuum Inaccessibility for maintenance or re-lubrication The presence of vibrations, extreme loads and stresses Contaminants generated by processes Petroleum-based lubricating substances work effectively only when: Operating temperatures are in the broad range of -4°F to 212°F (-20°C to 100°C) Tribology parameters enable the lubricant film to be formed within interacting surfa