How to clean the crane's hydraulic system
The cleaning ensures that the hydraulic system can work normally and the work tasks can be completed efficiently. 1. Hydraulic component cleanliness requirements Some components and assemblies are connected to the cleaned main system, and the cleanliness of these components is much better than the cleanliness of the system. The proof of the cleanliness of the components that the hydraulic component supplier should provide can be found. If component cleanliness cannot be found from the component supplier, the system installer must follow these specific procedures to clean these components. However, if the supplier's cleaning does not meet the requirements, the cleanliness certification cannot be considered valid. Note: If components have anti-corrosion additives that are incompatible with the hydraulic media, they should be rinsed with 5%-10% degreasing additives. The degreasing additive must not be selected to damage the component seals. 2. System flush preparation 2.1. Pipeline Mechanical Cleaning Length of steel pipe - cutting, bending, welding and removing scales and corrosives - chemical cleaning and hot oil flushing. The welded pipe should use plastic pigs for internal mechanical cleaning. A plastic pig is a plug with a brush, a scraper and a roller on its outer surface. It moves within the pipe under the effect of oil pressure to achieve a cleaning effect. This will ensure that the flanges of the pipe and pipe are smooth and remove weld slag and foreign particles. All steel pipes and hoses must be carefully inspected and purged with highly filtered industrial compressed air. This removes the larger particles that occur when the steel pipe is cut and the hose joint is installed. 2.2. Short circuit of important components In order to effectively clean all components in the system and to avoid damage to sensitive components, the relevant components must be short-circuited or removed from the flush circuit. Each component or subsystem must be thoroughly cleaned to meet the cleanliness requirements. When flushing the piping system, disconnect all components and systems that will restrict flow and components that may be damaged during flushing. 3. Chemical cleaning and hot oil flushing Each flush circuit must be connected to obtain a specific flow rate and Reynolds number, and all components, piping, and fittings have sufficient fluid pressure to avoid particles remaining in the forbidden areas and dead ends. The flushing flow and pressure must also be taken into account. 3.1. Chemical cleaning According to the DEWA DPI system, chemical cleaning consists of special chemicals that are placed in the same acid-alkaline tank. DEWA is Greek for “strong and vitality†and DPI stands for Degreasing, Pickling, and Inhibiting, developed by DPI Chemical Industries, Norway. All chemicals are water-soluble, environmentally friendly and inorganic. The cleaning process consists of the following 5 stages. a. Degreasing and caustic washing The tank is filled with fresh water, heated to 50C (up to 80C), and chemical substance A is added to PH 14. At maximum flow for 30 minutes, any grease and oil film should have been removed. The pH and temperature should be controlled during operation. b. Pickling Chemical substance B was added to reduce the pH to 5.5 and 10% (by volume) of chemical substance C was added. Cycle at maximum flow for 60 minutes. Pay attention to control the pH and temperature. c. Neutralization Chemical substance D was added and the cycle was continued until the pH was 7.5 and the temperature was maintained at the temperature of the procedure a. And circulate at maximum flow for 30 minutes. Pay attention to control the pH and temperature. d. Chemical preservation If the interval between chemical cleaning and hot oil flushing is less than 24 hours, do not add preservatives. If the interval is greater than 24 hours, 2% (volume ratio) of chemical substance E must be added, and heating is continued for 30 minutes without heating. These liquids must be filled with 4-5% water before dilution to control the pH. e. Drying After neutralization, the pipe was dried with dry hot air for 30 minutes. Use effectively filtered oil-free dry compressed air or clean nitrogen. f. Flushing equipment · Acid and alkali washing station: oil tank, oil pump, filter and heating equipment. The flushing flow rate is preferably 3m/s. The filter should be chosen the same as when cleaning with hot oil. · Equipment that supplies dry, clean hot air or nitrogen. The air must be absolutely free of oil. Special flanges, valve blocks and fittings, and cleaned in advance. g. Control during cleaning In order to identify whether chemical cleaning is correct, the following test data must be recorded: · PH value · Temperature · The amount of chemical substance added at each step · Traffic 3.2. Hot oil flushing In general, the target cleanliness of the system flush should be better than the cleanliness during normal operation. If the cleanliness requirement for the normal operation of the system is ISO 15/13/11, then the system should be flushed to at least ISO 14/12/10. Flushing must meet both the cleanliness requirements of solid particles and moisture 3.2.1. Flushing media The flushing medium must have good compatibility with the medium during normal operation of the system and should give viscosity at different temperatures. If the rinsing oil has a viscosity of 10-15 cSt at 40C, a standard rinsing station can provide sufficient turbulent flow. In theory, as long as the temperature is not higher than 70C, the viscosity can be achieved by flushing the oil. In actual operation, the working medium is usually selected as the rinsing medium. 3.2.2. Turbulence, flow rate, temperature and pressure Turbulence and Reynolds number When the Reynolds number is greater than or equal to 4000, fluid movement will naturally be turbulent. The turbulent flow can effectively wash away the particles in the pipeline and avoid the suspended pollutants in the oil during operation. The Reynolds number at which flushing is required is greater than or equal to 1.2 times the Reynolds number in normal operation, but should be at least 4,000. For example, the Reynolds number of a hydraulic system during normal operation is 3400, and the Reynolds number during flushing should be at least 4080. The Reynolds number Nr is a laminar or turbulent flow that is used to determine the flow of a fluid in a pipeline. Its calculation formula is: Nr = ÏνD/η Ï = fluid density ν = average flow rate D = pipe inside diameter η = dynamic viscosity The dynamic viscosity η = Ïμ (μ is the fluid kinematic viscosity), solid Nr can also be calculated by the following formula: Nr= νD/μ For example, a hydraulic fluid with a viscosity of 46 cSt flows in a pipe with an internal diameter of 800 px at a flow rate of 4 m/s. Its Reynolds number is: Nr=(10000px/s)(800px)/(11.5px2/s)=2000 On the surface of experience, it is laminar flow when Nr<2000; Nr>3000 is turbulent flow; Nr is unstable flow between 2000-3000, changing between the two modes. · Flow rate The flow rate should not be less than 2-3m/s in any flush circuit, which prevents particles from remaining in the pipe unit. · Temperature The temperature of the coldest part of the flushing circuit should be higher than 50C. This can be achieved by providing 60C flushing oil. · Stress Measured from the downstream return filter of the flush circuit and before the sampling port, the pressure should be greater than 3-5 bar. To ensure that all areas are effectively cleaned, the hydraulic components should be fully open. 3.2.3. Cleaning of tanks, filters, cylinders, accumulators, pumps, and motors These components should be cleaned in different circuits. • Tank: This is one of the most difficult components to clean in the system. The tank should be manually cleaned and then flushed with a flushing pump and filter to form a circuit for flushing. • Filter: A flush circuit or a separate tank flush circuit can be connected. · Cylinder, accumulator, motor and oil pump: cleaned separately. 3.2.4. Shortest flushing time Once the rinse oil sample shows that the cleanliness level has been achieved, it is flushed for an additional 30 minutes in turbulent flow to increase the reliability of the rinse. 3.2.5. Evaluation of Rinse Results Each flush circuit should be unique and trackable. Establish the actual intent of the flushing circuit and the corresponding piping, marking temperature points, flow detection points and sampling points. All parameters are documented, such as the start of flushing time, temperature, flow, particle contamination, moisture, and end time. If you may be looking for a third party to assess the cleanliness of the system flush. 4. Flushing equipment 4.1. Filtration System The filtration system should have sufficient capacity and high performance to be able to filter out solid particles and moisture in a reasonable amount of time and achieve cleanliness requirements. The original filter in the system should not be used as a flush filter. The latest practice shows that with a pressure differential signaling device, there is a large enough volume to contain contamination, and a filter with β3 > 100 is very effective. The sending device shall give an alarm before the filter is actually bypassed (the filter does not function as a filter). Moisture removal can be done in a number of ways: using water-absorbent filter elements, combined filters, oil purifiers (eg vacuum distillation), or simply changing the oil. In general, absorbent filters are effective. Note: Do not replace the filter that filters solid particles with a water removal filter! 4.2. Pump Station The pump station should provide enough flow, flow rate, viscosity and pressure to clean the system. 4.3. Temperature Regulation System The temperature should be constantly checked and adjusted to ensure that the rinse oil has the proper viscosity so that turbulent flow forms throughout the flushing circuit while satisfying the lubrication requirements of the flushing oil pump. 5. Detection of system cleanliness during flushing 5.1. Cleanliness of the system during normal operation (NAS or ISO 4406): According to the equipment manufacturer The requirements are ok. If equipment manufacturers do not explicitly request, it is recommended not to be lower than ISO 4406 17/14 or NAS Level 8 5.2. Target cleanliness of the system flush: Two orders of magnitude lower than normal operation. Normal work When working in NAS level 8, the target cleanliness level for rinsing should be NAS level 6. 5.3. Detection of cleanliness: Can be performed in a laboratory or portable cleanliness detector On-site inspection. The following figure shows the PALL portable contamination tester, which can be inspected by Meifu engineers on site. Cleanliness detection cycle: It is specifically formulated according to site conditions. Sampling: It is best to take a sample at the return tank of the return header (sampling valve must be installed on the return header). Sampling Container: Clean sampling bottle. The above is the hydraulic system cleaning of the crane. I hope it will help everyone. Prefab Container,Equipment Container Integration,Prefab Equipment Container,Integrated Container For Equipment Yangzhou Tonglee Reefer Container Co., Ltd. , https://www.cimctlc.com