Preventive Maintenance Strategy of Environmental Test Chamber Based on Particle Swarm Optimization Algorithm

With the development of various physical industries, people pay more attention to reliability tests and test equipment. To solve the problem of making maintenance strategy of an environmental test chamber for reliability test, a periodic preventive maintenance strategy based on RCM(Reliability Centre Maintenance) is proposed. Firstly, a multi-objective optimization model of reliability and maintenance cost is established by combining reliability theory and life distribution theory, and two objectives of equipment reliability and maintenance cost are considered. Secondly, the actual environmental test chamber fault maintenance data is analyzed, and it is found the fault distribution meets the dual parameter Weibull. Finally, the particle swarm optimization algorithm is used to solve the multi-objective model optimization, and a series of Pareto optimal solutions are obtained, that is, the number of maintenance times and the corresponding time interval in the operation cycle of the environmental test chamber, and these solutions might be good references for maintenance management personnel.

Measurement of indoor environmental parameters and analysis of the condensation phenomenon in urban utility tunnels

Condensation is a major issue in the safe operation of utility tunnels. To address the condensation problem, the indoor air temperature, relative humidity (RH) and surface temperature in an urban utility tunnel in Jining were continuously measured, and the condensation conditions were surveyed and analysed. The results indicated that under natural ventilation conditions, the air temperature in the comprehensive cabin varied from 23.4°C to 24.5°C, the RH fluctuated between 86.4% and 95.3%, and the corresponding air dew point temperature (DPT) remained in the range of 22.2°C–22.9°C. The surface temperature of the water supply pipeline ranged from 17.8°C to 18.5°C, which was far lower than the DPT in the tunnel, resulting in serious condensation. A water supply pipeline with an anti-condensation design was developed based on environmental test data. A 25-mm-thick rubber plastic sponge insulation layer was used to thermally insulate the water supply pipeline, preventing further dew condensation. Furthermore, mechanical ventilation had little effect on reducing the RH in the tunnel and may actually cause dew condensation; therefore, a ventilation control mode was proposed in this study. These results are expected to provide basic data for further research and reference for the safe management of utility tunnels.

Environmental test of improved in vitro potato varieties in the conditions of Central Yakutia

Ecological tests of improved in vitro plants - potato regenerants of promising and zoned in Central Yakutia varieties have been carried out on cryogenic flood plain fibrous saline soils. To conduct a field experiment, clones adapted to the soil (2019) and their tuberous offspring (2020) were planted at the end of May. It was revealed that the most resistant to open ground conditions were regenerants of the Krasavchik variety (survival rate - 28.0 %); the least adapted variety was Vasilek (1.0 %). It has been established that among improved zoned varieties the most tolerant to arid conditions of vegetation (hydrothermal coefficient 0.4) and more productive (average tuber weight 213.9 g) was the Adretta variety. High index of tuber safety (100.0±5.0 %) was observed in Adretta variety (37 pcs.) and promising varieties Riviera (18 pcs.), Triumf (40 pcs.) and Rodrigo variety (16 pcs., 94.1±4.7 %). Zoned variety Vasilek (12 pcs., 80.0±4.0 %) and promising variety Assol (77.3±3.9 %, 17 pcs.) had no statistical difference in these indexes. The safety of Krasavchik variety tubers was 69.1±4.0 % (241pcs.). Zoned variety Rozard (65 pcs., 55.6±2.8 %) and promising Ilona variety had the same tuber safety. Minimum level of tuber safety was observed in Velina variety (18 pcs., 33.3±1.7 %).

Control of low frequency noise from an environmental test facility

Environmental test chambers are used in the automotive industry to verify the resilience of vehicles. In just a few hours it is possible to take a car from mid-winter in the artic, via a high mountain range, to mid-summer in a desert. Powerful ventilation systems are used to change the temperature, pressure and humidity of the air in the chamber, and the variable speed blowers are a major source of low frequency noise, which can cause significant disturbance at neighbouring properties if there are gaps in silencer performance. This paper details a study to assess the attenuation requirements for a system to meet a standard criterion for low frequency far-field noise levels, and to select a reactive silencer system to achieve that specification under all circumstances. The system used standard silencer components where possible, but needed to take account of long pipe runs through the facility, with tailpipe resonances being a particular issue, and was further constrained by space and loading limits for the building. Design layouts were verified using the Actran FE code, taking account of interactions with existing silencers and transfer functions to the far-field, in order to have very high confidence of a successful outcome.