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1 Purpose 1). Appropriate measures should be taken to remove rust and scale from within the pipes, as well as other debris attached to them. This also helps to save time spent on oil flushing. 2). The acid cleaning of oil and auxiliary pipelines should be carried out in accordance with the operational guidelines outlined in the diagram. 2 Acid Cleaning Procedures Acid cleaning of carbon steel pipes Generally, for acid cleaning carbon steel pipes, liquid phosphoric acid is preferred to prevent rust from adhering to the pipes after cleaning. However, if hydrochloric acid or sulfuric acid must be used, appropriate inhibitors should be employed, and the acid must be in liquid form to avoid over-cleaning. Acid cleaning of stainless steel pipes For stainless steel pipes, a solution of nitric acid and fluorinated acid should be used. Nevertheless, nitric acid produces toxic gases, and fluorinated acids can damage human nerves; therefore, special attention must be paid to ventilation to eliminate this risk. Additionally, fluorinated acids can destroy cell tissue upon contact with the human body. In case of exposure, the affected area should be rinsed thoroughly with water immediately, and appropriate medical treatment should be sought. The procedures for pipe acid cleaning are as follows. Preparations for oil flushing Temporary filtration 1). Install a temporary filter made of wire mesh with 100–120 mesh density in the manhole at the top of the oil tank, or fit a conical temporary filter on the oil return pipe of the tank. When the amount of dust filtered by these filters decreases, replace them with wire mesh having 200 mesh density until the process is completed. 2). Temporary filters are used to check the condition of supply pipes for lubricating oil, sealant oil, and/or governor oil. All supply pipes should pass through bypass pipes connected to the pipes used for flushing the oil lines. Temporary bypass pipes Temporary pipes should be constructed using steel pipes and/or reinforced high-strength polyethylene hoses or rubber hoses, in the order specified below. Bypass pipes made of carbon steel must be thoroughly acid cleaned. Polyethylene or rubber hoses must be able to withstand high temperatures (80°C) and must be new hoses, meaning those without any impurities inside. 1). The installation of temporary bypass pipes should start from all supply pipes located near the compressor’s flanges and those on the bearing housings of its drive motor, all the way to the flanges of the pipes used for flushing on the oil drain pipes. 2). Install temporary pipes to replace control valves. 3). If the compressor is driven by a steam turbine, temporary bypass pipes equipped with valves or flow control orifices with a diameter of 10–15 mm should be installed on the governor oil supply pipes located on the bearing flanges of the steam turbine. These bearing flanges are closest to the flanges of the pipes used for flushing on the oil drain pipes. At the points where temporary pipes are installed between the oil supply pipes and the drain pipes, near the throttle valve cylinders and/or extraction check valve cylinders, the connections between the supply pipes and the drain pipes should be disconnected. The oil used for flushing should be supplied from the governor oil supply pipes closest to the steam turbine’s governor flanges. The typical procedure for oil flushing is shown in the diagram below. Notes: 1). It is recommended not to use rags to replace control valves; cloth fibers can easily get damaged and fall off. 2). Once the above tasks are completed, close the manhole and shut off all valves. 3). Use wire mesh with 200 mesh density to pour the flushing oil into the oil tank. The recommended flushing oil is described in separate documents; the amount of oil used should be kept above the minimum operating level while the oil pump is running and both oil coolers and oil filters are filled with oil. Flushing pump During oil flushing, a motor-driven oil pump should be used. 11.2.7 Operations for heating and cooling oil 1). Heat the oil in the oil tank using steam-heated coils and/or embedded electric heaters in the tank. 2). Cool the oil by using the oil coolers installed in the oil operation panel. Tools and instruments required for oil flushing Before starting the flushing process, the following tools and instruments should be prepared: 1). Tools: Chisels with wooden handles, wrenches, etc. 2). Instruments: Pressure gauges and thermometers. 3). Various other equipment. Oil tanks and/or barrels for transporting oil and containing leaks, as well as any materials needed for flushing. 4). Mesh sizes of wire mesh: 100 and 200 mesh. Oil flushing procedure Once the preparations for oil flushing are complete and it is confirmed that the oil circulation is normal, the oil flushing process can begin. Oil flushing flow rate The greater the oil circulation rate, the higher the flow velocity, and thus the better the flushing effect. However, care must be taken to ensure that the pump and drive motor do not exceed their capacity limits. Adjusting the flow velocity by manually operating the valves on the various pipes can also improve the flushing effect.