Pressure and air leakage assessment Shanghai Ingersoll Rand Compressor Co., Ltd. (200000) Pan Zhi compressed air leakage principle, the impact of leakage on production and management, three different methods and steps for leak detection, quantitative calculation of leakage The principle and introduction of the main means of repairing compressed air leaks. It has certain application value to enterprise management personnel and leak detection practitioners.
The front acre compressed air is one of the most widely used power sources in the industrial field. Due to its advantages of safety, pollution-free, good regulation performance and convenient transportation, it is widely used in the field of automation. Compressed air is also an expensive source of energy. Continuously reducing the operating costs of compressed air is an important issue for every plant manager.
Compressed air leakage is almost the most common energy waste in the factory. The average compressed air leaks 30% of the total compressed air, which means that tens of thousands of electricity bills are leaked every year. Some leaks are very obvious. Not only does it emit a lot of noise, it can even detect leaks through touch and vision. Some leaks are very concealed. In addition to being too small to hear sounds, "hidden" leaks often occur in environments with high background noise in the workplace. All of the above leaks constitute a source of leakage throughout the system. Leaks typically occur in pipe joints, push-in fittings, pressure regulators (FRL), frequently opened condensate drain valves, broken hoses, and broken pipes.
Leakage is a common phenomenon in air systems. A properly functioning system is difficult to avoid. According to the results of the US Department of Energy (D0E) survey and the author's long-term experience, there is a leak in every system, and nearly 60% of the factories have not taken any measures for leakage in the air system.
Leaks in the factory are ubiquitous. If a factory wants to completely eliminate the leak, it is almost impossible. What we can do is to control the leakage of compressed air within a reasonable range. This "reasonable" range and the size of the plant have a lot to do with the old and new: 1) For new systems (less than 1 year) or small factories, the leak rate is controlled at 5% 7%. 2) For 25 years of system or For medium-sized plants, the leakage rate is 7% 10%. 3) For systems or large plants over 10 years, the leakage rate is 10% and 12%. Leakage not only directly leads to energy waste, but also indirectly leads to energy waste. When the leakage increases, the pressure of the entire compressed air system will drop. If it is desired to maintain the pressure of the air system, additional compressors must be opened, which will further increase the cost of electricity throughout the plant. In some plants, there are a large number of intermittent discharge devices, such as electronic drain valves, which discharge condensate or other waste liquid at regular intervals. When the waste liquid has been drained during the discharge time, a large amount of compressed air will be Leave the compressed air system. At some point, there may be multiple discharge valves simultaneously venting, and the pressure of the entire system will suddenly drop, even exceeding the minimum pressure that the system can accept, causing the entire system to stop production. This is a typical operational accident.
General-purpose machinery Since compressed air is produced by the work of an air compressor, and the air compressor is dragged by the motor, the leakage of air indirectly means waste of electric energy. Quantitative compressed air leakage is a relatively complicated task. Under different air pressures, different sizes of leakage points and leaking air apertures / mm leakage points gauge pressure / MPa leakage / in practice, there are three methods often used to quantify Evaluate the amount of leakage of compressed air.
(1) The gas storage volume measurement method assumes that an air system is closed, and only the leakage is the only way to exit the air system as compressed air. For the compressed air system, the following leakage calculation formula is: p absolute pressure, unit is bar; V - leakage The amount of air, in units of in3; T test time, in min. If an air system, its total gas storage volume (including gas storage tanks and pipelines, etc.) is 6rn3, the leakage of compressed air leads to the 3rnin inner gas storage tank The pressure dropped from 7bai' to 6bai', then the leakage amount Q=2inVinin, and a total of 6m3 of air was leaked within 3min.
(2) Compressor operation measurement shuts down all gas equipment in the air system to ensure that all air in the compressed air system leaves the system in a leaky manner. Open a compressor, use the unloading die, still supplying air, but the unstarted machine, drain valve, quick-connect connector, etc., can draw a most suitable detection route during the inspection process, and draw a pipeline diagram when possible. It is very helpful to determine the leak point in the future.
Some air lines, remember to wear headphones all the time, when it is difficult to determine the leakage direction, you can adjust the sensitivity.
The direction finding uses the end to advance.
Enter the hall to avoid repeated inspections or missed inspections.
Mark the position to ensure that the leak label can be hung at the leak point at least until the leak is eliminated (recommended not to be removed for retesting).
6) Test again after the leak has been repaired. Sometimes the repair will result in a new leak.
In practice, the leak detection service work often combines the above multiple methods: the total leakage of the air system is calculated by the gas storage volume measurement method and the air compressor operation measurement method, and the result is used as a management decision to determine whether to perform specific leak detection. Basis. The ultrasonic leak check method measures and marks each specific leak point. After finding and quantifying the compressed air leak point, using the data statistics method, you can easily get a leak list and plan the scope of the next step to repair the leak. Since repairing leaks can incur costs, Pareto optimal analysis is often used in practice to determine the priority of repair. The following figure is a Pareto analysis of all leaks commonly found in leak detection reports. Only need to leak the largest leakage of general machinery
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