checked by videoendoscopy, is usually neglected. Proper preparation of the oil system, comprehensive cleaning done by machine overhaul, new builds and modernization is crucial element for long term machine reliability. What one can do when severe deposits, sludge, varnish or rust formation has occurred in the responsible oil system of turbo-machinery? How to clean newly assembled oil system that is corroded, contaminated with chemical preservatives or machining debris? Moreover, what can be done with big quantities of wear debris inside the oil system after severe seizure and breakdown of the bearing? How to clean it effectively? Aus Wissenschaft und Forschung 34 Tribologie + Schmierungstechnik · 69. Jahrgang · eOnly Sonderausgabe 1/ 2022 DOI 10.24053/ TuS-2022-0030 1 Introduction Besides the common repairs and maintenance, modernization of the machine usually takes place with strategy of efficiency increase. Other reasons are change of steam parameters where machine is modified following the need of steam parameters in production area of the plant. The expected machine availability is in all cases high and oil system cleanliness plays big role in machine reliability. It seems that the role of oil analyses in industry is understood and proper condition of the oil based on applied analyses program is monitored and maintained. Oil systems are being equipped with different types of purification units where customer nowadays is lost which technology to choose and employ. Turbine oils are highly refined and hydrocracked which leads to higher thermal and oxidation stability on one hand, but tends to produce and built Varnish during operation on the other hand. The level of oil system maintenance is in many cases improved, the oil monitoring usually applied. Oil manufactures offer high quality turbine oils and there are variety of technologies in oil conditioning. However, the cleanliness of the oil system itself, cleanliness of pipes How to commission the turbine oil system that was over years out of operation? Can heavily corroded and deposited turbine oil systems be restored Tomas Klima, Wojciech Majka* Preparation of rotating machinery oil system plays very important role in commissioning process and defines if commissioning process of the turbine brings some troubles. Moreover, future maintenance and operation is very much affected if oil system cleanliness is underestimated and machine commissioned without following complex cleaning procedure. Only standard displacement flush is not effective when system is corroded, where Varnish is agglomerated, pipe assembly done on site with lack of proper care. However, high machine availability and zero breakdowns is nowadays the main goal in every industry sectors! How to restore heavily corroded and Varnished turbine oil system after 10 years out of operation will be presented in this presentation. Keywords rotating machinery oil system, turbine, maintenance, cleaning, corrosion, varnished Abstract * Tomas Klima, MSc Eng Ecol Industrial s.r.o. (sister company of Ecol Sp. z o.o.) Czech Republic Wojciech Majka, MSc Eng. Ecol Sp. z o.o., Rybnik, Poland Figure 1: Uncleaned oil system causing journal bearing overheat, vibration and wear Contaminants must be removed from oil systems for trouble free operation. However, in many cases the standard method of oil flushing is not effective enough and usually takes a lot of time when flushing is performed properly (high flow rate, change of temperature and flowrate, absence of large particles in the oil and on metal meshes, target cleanliness). It is recommended to plan and schedule comprehensive check of the oil system interiors by employing videoendoscope, visual check, shooting photographs and its combination. It is very useful to do it with a certain frequency in order to monitor the level of contamination or corrosion process and also evaluate the uncertain results from oil analyses. Highly recommended is to schedule videoendoscopy check also before closing the bearings and installation of repaired components to avoid oil system contamination from dust, machining particles, insulation and other material. Flushing them out before machine commissioning may takes weeks if this fact is underestimated. of the particular turbine/ compressor for the next long period of operation with the focus on maximum reliability. 2 Problem of dirty oil systems Despite of wide application of high quality filters, developed oil analyses programs, high performance lube oils, there are still problems causing bearing failures, inappropriate working hydraulic systems and changes of physical parameters of the oil especially after the oil exchange. Impurities enter the oil system either during the new assembly as well as execution of overhauls (metal debris from machining, welding slag, sealants and other materials used for assembly/ repairs) or simply from the ambient. Furthermore, impurities are generated within the operation due to oil degradation, water contamination from oil coolers or steam glands leaks or ambient humidity that condensate in oil reservoirs, gear boxes and speed up the corrosion processes. Often in process machinery (air/ gas compressors) compressed gas is carrying different impurities and can itself interact with oil (with oil base or oil additives) while entering the oil system through wet seal glands of sealing systems. Aus Wissenschaft und Forschung 35 Tribologie + Schmierungstechnik · 69. Jahrgang · eOnly Sonderausgabe 1/ 2022 DOI 10.24053/ TuS-2022-0030 Figure 2: Corrosion, oil aging products in the oil system pipes inspected before turbine modernization Figure 3: Oil aging deposits in the inspected - return line from turbine control valve In cases, where oil system is corroded or Varnish formation is observed, there are certain cleaning methods for restoration of the pipeline cleanliness. One of them, like steam blowing is less effective and not more used for safety reasons. Other method, like chemical cleaning is not recommended for high contamination potential of new oil. Alternatives are cleaning of oil systems with dosed detergent or other solutions that increases the solubility of Varnish contamination. Compatibility with the new oil and cleaning effect must be taken into account before applying that method and considered if Varnish is the only contamination source. Besides that, consideration of flushing scenarios and its effects. In order to displace fully or partially dissolved deposits and flush them out from surfaces and components, laminar flow flush is not usually effective method. While planning the shutdown or partial overhaul, there is a key question, how to maintain the oil system Impurities are the main cause of premature wear of elements and could lead to equipment breakdown. The most vulnerable parts include bearings, hydraulic actuators and controllers of control systems, gearboxes, drive-shaft seals, pumps (especially hydraulic and jacking system pumps) oil coolers as well as oil filters and oil reservoirs. Very troublesome group of impurities are oil degradation products from oil ageing and thermal stress creating insoluble chemical compounds that are responsible for varnish and sludge formation. cles attached to the sticky layers of Varnish or sludge. Rust that usually builds up in the return lines is also not properly removed. Effective cleaning method with clear prove of its cleaning effect in every moment is hydroblasting/ hydrojetting of the oil system pipeline and components. High pressure water stream/ water jets do penetrate the corrosion, Varnish layers and loosen them from the surface. Outflowed water displace the contaminants from the pipes. Each end every pipeline (discharge&return lines, suction pipes, overflow pipes and complete oil system piping) are intensively cleaned by this process. 4 Description of Ecol technology Based on long term experience in power generation, Ecol is offering a technology where the whole oil system is intensively cleaned/ hydroblasted with high pressure water jets and subsequently flushed with high flow rates (turbulent oil flushing). This technology is as an excellent alternative to other (often insufficient and obsolete) methods. Below described cleaning and flushing technology is most likely the most effective method of preparing new oil systems and restoring operated oil systems regardless of their size and complexity for future reliable operation. Presented technology consist of three phases: I. hydrodynamic cleaning using water at very high pressure (up to 150 MPa); II. flushing of the oil system with oil at high (turbulent) flow rates and with full-flow absolute filtration III. post-assembly by-pass oil filtration prior to turbine/ compressor start-up. The core of this technology is cleaning of all inner surfaces of oil system with high pressure water jets utilizing suitable nozzles (appropriate for water pressure and tube’s diameters), immediate drying and application of protective turbine oil spray to dried surfaces followed by flushing with continuously filtered oil at sufficient pressure and flow rates. Phase I: Intensive cleaning of the oil system using high pressure water (pressure up to 150 MPa) - “hydroblasting” The inner surfaces of the system are intensively cleaned/ blasted with high pressure water in order to remove soft deposits (loose wear debris, sand and dust grains, products of oil ageing process, sludge, biological deposits, resins and asphalts; greases and corrosion-protec- Aus Wissenschaft und Forschung 36 Tribologie + Schmierungstechnik · 69. Jahrgang · eOnly Sonderausgabe 1/ 2022 DOI 10.24053/ TuS-2022-0030 The fact of having fine filters, performing periodically oil analyses or just considering application of high performance lube oils leads to the underestimation of the cleanliness of the interior of the oil system itself. The overhaul of the responsible machine together with planned oil exchange is usually the factor of future difficulties. Components of the oil system used to be disassembled, controlled, repaired or exchanged and the dust, machine debris or different chemicals (silicon, grease paste, cleaners) get into the oil system on different places. Subsequent oil flushing is done usually at the end of the overhaul/ shutdown where longer period of flushing is bringing troubles. It’s not unusual that the oil is contaminated with different kind of chemicals and foaming tendency, air release properties or deemulgation are significantly influenced. Condition of the interiors of the oil system should not be neglected but rather included in the maintenance/ overhaul planning. Periodical inspection helps to avoid timeconsuming oil flushing of the dirty oil system and enable to plan intensive cleaning of the whole system. 3 How to restore/ clean heavily corroded and Varnished turbine oil system? When corrosion and/ or Varnish in machine oil system is observed effective and proven cleaning is necessary. Oil system made from carbon steel operated with increased water content are usually corroded due to this fact but not only. Most of available standards or recommendations or just industry practices put big attention to flushing process before system start-up. In fact, the common procedure of oil flushing base on the performance of oil system pumps, that generate limited flow. In the system where corrosion, sludge or varnish as well as deposited particles are present is very difficult to flush the system effectively. The flow is not big enough to loosen all parti- Figure 4: Photo of oil cooler covered by varnish tive layers such as tectyl, naphta) as well as hard deposits (such as corrosion products - rust, welding slag on welds, varnish residues, machining residues partially attached to surface). elements of the oil system (pumps, valves and fittings, coolers, etc.) must be disassembled. Completed cleaning is followed by immediate drying of cleaned surfaces using filtered compressed air and application of protection layer of turbine oil (oil spray) preventing secondary corrosion of cleaned oil system. Oil system remains completely dry after hydrodynamic cleaning phase therefore risk of ingression of water into oil during flushing is completely eliminated. Phase II: Flushing of oil system with fully filtered oil flowing at very high flow rates (high velocity oil flush) In order to remove impurities that were detached with high pressure water, but not successfully carried out by water stream, effective oil flushing is needed. Using external, high capacity oil pump and fine filters ensures reaching high velocities of the oil. By-passing the bearings, oil pumps of the system, servo valves, allows to perform this service in advance of the final startup and shorten the overhaul time. Aus Wissenschaft und Forschung 37 Tribologie + Schmierungstechnik · 69. Jahrgang · eOnly Sonderausgabe 1/ 2022 DOI 10.24053/ TuS-2022-0030 Figure 6: Oil pipeline after hydroblasting (compare to Figures 2,3) Figure 8: Turbulent flushing with full-flow absolute filtration (schematic) Figure 7: Thoroughly and perfectly cleaned oil cooler bundle Figure 5: Hydroblasting process (schematic and real) The following activities are carried out in the course of the cleaning process: ■ high pressure water cleaning (operating pressure 75-150MPa) of all interiors of pipelines and other elements of the oil system: pipelines - lube, seals, lever (jacking) and hydraulic systems; coolers and reservoirs; bearing stands etc.; using suitable equipment (elastic lances and nozzles; water guns etc.); ■ immediate drying of cleaned surfaces using filtered compressed air; ■ application of anticorrosive protection on dried surfaces until flushing (spraying of inner surfaces with lubricating turbine oil); ■ protection of open flanges against dust and dirt from ambient until the flushing process takes place. Comparing to other methods this technology does not require the disassembly of the whole system. Only few Phase III: By-pass oil filtration before or during system start-up In order to remove post-assembly impurities (introduced during assembly and disassembly works done after flushing) performing of by-pass oil filtration is done. Oil system pumps are in operation and oil flows already into the bearing, seals, hydraulic components and back to the oil tank. The filtration of the oil is done shortly reaching back the required cleanliness. Aus Wissenschaft und Forschung 38 Tribologie + Schmierungstechnik · 69. Jahrgang · eOnly Sonderausgabe 1/ 2022 DOI 10.24053/ TuS-2022-0030 Oil systems of the turbine or compressor are flushed using special filtration and pumping units (flushing skids equipped with absolute filters β5 > 1000) ensuring turbulent flows at flow rates ranging from 8,000 to 20,000 l/ min. The units have appropriate operating parameters and are connected to the oil system using hoses, manifolds, flow distributors where bearings, servomotors and other flow restricting-elements are by-passed. Figure 9: Flushing skid connected to the oil system of large utility steam turbine with high capacity oil filters (full flow filters) Figure 11: Off-line oil re-filtration before start up (schematics) Figure 10: High velocity oil flush - bypasses/ jumpers installed on large utility steam turbine Flushing is performed using fresh turbine oil, which will remain in the system for further use (extra batch of flushing oil is eliminated). The flushing process continues until predetermined purity criteria are reached in each location of the system. During this time oil temperature and flow direction are changed in order to move out remaining impurities. Effective flushing of the turbo compressor oil system is based on the following three important criteria: I. Flow rates at all pipeline sections should be sufficient to invoke turbulence (Reynolds number for the pipeline Re > 4000). In-pipeline flow velocities are measured using ultrasound flow rate meters. II. Oil cleanliness class better than required by turbine manufacturer (e.g. most often 16/ 14/ 11 or 17/ 15/ 12 acc. to ISO 4406). The cleanliness is measured in various locations of the system (inlets to the bearings, seals, servo valves). Common cleanliness after 3-4 days of flushing is 15/ 13/ 10 and better. III. No solid particles larger than 150 microns deposited on 150 µm mesh strainers installed in strategic locations of the system (inlets to friction nodes - lubricated elements). Other than 150 microns (smaller) sizes can also be warranted if agreed. 5 Conclusion The above described technology of hydrodynamic cleaning and turbulent flushing is very effective and advanced method of restoring old oil systems as well as preparing new systems for first start-up. It allows to run the machinery out of failure in the means of lubrication and secure trouble free operation to the next shutdown and even much longer. • The technology allows to renew less or more dirty and corrodes systems (to “like new” condition) and is also suitable for new assembled oil systems. • Hydroblasting shortens future flushing process because most of impurities are got out by water. Only little amount of loosen deposits remain in the system and are later easily flushed out. • Oil analyses performed in operation are providing adequate results that aren’t influenced by old deposits, debris, particles. Detecting wear process is precise and accurate (avoidance of confusing ‘background’ impurities). • Varnish and other aging products as well as chemicals are completely removed. No risk of contamination of the new oil or changing its parameters. It’s very useful before oil exchange. • The method is entirely safe for the natural environment, since pure water is the cleaning medium and the wastewater (rest of oil and water) is easy to dispose. • Flushing after hydroblasting is very fast and efficient. Time for flushing is easy to plan and schedule. No risk of long lasting flushing comparing to other methods. • Possibility of long-term warranty of the oil system cleanliness for the customer. It guarantees improve both, economical and technical factors: ■ long-term purity of oil and system itself ■ reduced quantities of flushing oil batch in the process ■ reduced wear of lubricated parts and extended MTBR ■ increased life time of the oil and machine components ■ higher equipment availability ■ significant reduction of oil filter consumption ■ no turbine outages due to dirt in the oil system ■ reduced total operation cost This method is becoming a preferred choice of OEM and maintenance/ repair companies. Now since year 1994, over 700 different turbines’ oil systems have been serviced by Ecol according to the presented technology. The references contain (new commissioned as well as overhauled and modernized machinery): ■ turbo-generators (up to 1070MW; steam and gas turbines; including rich experience in nuclear power plants) ■ process turbo-compressors and blowers (hydrocarbons, synthesis gas, hydrogen, air, ammonia etc.) ■ boiler feed pumps with hydrokinetic couplings and gearboxes ■ large industrial diesel engines (including auxiliary power supply in nuclear power plants) ■ large gas and diesel engines ■ large hydraulic and lubricating oil systems in steelworks and rolling mills ■ central lube oil distribution systems in the plants etc. About authors Wojciech Majka, MSc Eng. (mech), MBA, STLE Member, is the President of the Board and CEO of Ecol Sp. o.o. (LLC) of Rybnik, Poland. Established in 1992 company is the leading professional service company delivering lubrication reliability solutions for industrial plants, especially for power plants, petro-chemical plants and refineries as well as for light industry such as automotive and drink&food processing. Tomas Klima, MSc Eng. (mech), is the director of International Sales Division, responsible for market and business outside Poland. Responsible for development and rich experience with Ecol services in Nuclear Power Generation. Core of Ecol’s scope of services includes lubrication management and execution (industrial oil service/ fluid management), lubricants distribution for power industry. Services include also advisory and lubrication engineering. However, the most world-wide known service of Ecol is unique technology of cleaning and flushing of oil systems (dedicated to turbo-machinery, large industrial diesel engines and power hydraulics). References [1] Majka, Wojciech; Klima, Tomas. Ecol Sp. z o.o. - own materials and internal Ecol company materials Aus Wissenschaft und Forschung 39 Tribologie + Schmierungstechnik · 69. Jahrgang · eOnly Sonderausgabe 1/ 2022 DOI 10.24053/ TuS-2022-0030 [6] Fitch, Jim. Noria Corporation, When to Perform a Flush? ; Machinery Lubrication 5/ 2004; www.machinerylubrication.com [7] Fitch, Jim. Noria Corporation, Flushing Strategy Rationalization; Machinery Lubrication 9/ 2004; www.machinerylubrication.com [8] Hannon, James B., ExxonMobil, How to select and service Turbine Oils; Machinery Lubrication 7/ 2001; www.machinerylubrication.com Aus Wissenschaft und Forschung 40 Tribologie + Schmierungstechnik · 69. Jahrgang · eOnly Sonderausgabe 1/ 2022 DOI 10.24053/ TuS-2022-0030 [2] Najfus, Jan. Comprehensive safeguard of the maintenance of the machinery room in Dukovany nuclear power plant; All for Power. Published 2/ 2010; pages 28-33. [3] ASTM D6439-05 - Standard Guide for Cleaning, Flushing, and Purification of Steam, Gas, and Hydroelectric Turbine Lubrication Systems; [4] Manuals and oil specifications of turbine manufacturers (Alstom Power; Siemens, GE, Doosan Skoda); [5] ASTM D4378-08 - Standard Practice for In-Service Monitoring of Mineral Turbine Oils for Steam and Gas Turbines;